The object was small, dry, and dark.<\/p>\n
It had survived in the sediment of an Oregon cave for thousands of years, long enough to become mineralized into a compact mass that archaeologists call a coprolite \u2014 ancient preserved feces.<\/p>\n
It did not look like evidence of anything extraordinary.<\/p>\n
It looked like something that should be ignored.<\/p>\n
Scientists did not ignore it.<\/p>\n
When researchers extracted material from coprolites found in Paisley 5 Mile Point Caves in south-central Oregon and ran it through ancient DNA analysis, they found human mitochondrial DNA.<\/p>\n
Specifically, they found genetic sequences belonging to Native American founding haplogroups \u2014 the maternal lineage markers that trace a continuous thread from the first people who entered the Americas to Indigenous communities living today.<\/p>\n
The coprolites were directly radiocarbon dated.<\/p>\n
When those dates were calibrated to calendar years, the oldest specimens fell in a range that researchers have characterized as approximately 14,200 to 14,300 years ago.<\/p>\n
That placed them before Clovis.<\/p>\n
The Clovis culture \u2014 defined by its distinctive fluted stone points, found at sites across North America \u2014 had been understood for decades as the earliest clearly documented human presence on the continent.<\/p>\n
Its archaeological horizon sat at roughly 13,000 to 14,000 calibrated years before present.<\/p>\n
The Paisley coprolites appeared to predate that by a meaningful margin.<\/p>\n
A discovery that should have closed an argument instead opened a fight.<\/p>\n
Within a year of the original publication in Science in 2008, published scientific criticisms appeared in the same journal.<\/p>\n
Was the mitochondrial DNA actually inside the coprolites when they were deposited \u2014 or had it migrated downward through the sediment from later layers?<\/p>\n
Could a non-human coprolite, lying in sediment where humans had also been present, absorb environmental human DNA?<\/p>\n
Were the cave’s stratigraphic layers genuinely undisturbed, or had mixing occurred?<\/p>\n
<\/p>\n
Was the radiocarbon dating compromised by contamination from old carbon in the groundwater?<\/p>\n
These were not hostile questions from people who wanted the discovery to fail.<\/p>\n
They were the normal and necessary questions that any extraordinary scientific claim should face.<\/p>\n
And the researchers who had made the original claim took those questions seriously enough to go back to Paisley Caves and build an entirely different kind of case.<\/p>\n
What followed is a story about how scientific skepticism, applied rigorously, sometimes makes a discovery stronger rather than weaker.<\/p>\n
The Caves at the Edge of an Ancient Lake World<\/p>\n
The landscape of south-central Oregon today is high desert \u2014 a spare, beautiful terrain of sagebrush flats, lava formations, and alkali lake basins that feels remote from almost everything.<\/p>\n
Summer temperatures can exceed 100 degrees Fahrenheit.<\/p>\n
Winter brings sharp cold.<\/p>\n
Rainfall is sparse.<\/p>\n
The dominant vegetation is the gray-green shrub carpet of the Great Basin, stretching to the horizon in every direction interrupted only by distant rimrock.<\/p>\n
It did not always look this way.<\/p>\n
During the late Pleistocene \u2014 the period relevant to the Paisley evidence \u2014 the northern Great Basin was a fundamentally different landscape.<\/p>\n
Pluvial lakes, fed by glacial melt and a wetter climate, filled basins across the region.<\/p>\n
<\/p>\n
Lake Chewaucan, which occupied the Summer Lake and Abert Lake basins of south-central Oregon, was one of these pluvial systems.<\/p>\n
At its maximum extent, it was far larger and deeper than the shallow remnant lakes and dry playas that mark its former extent today.<\/p>\n
The Paisley 5 Mile Point Caves are carved into a rimrock ridge above what was once the shoreline of Lake Chewaucan.<\/p>\n
The caves are solution cavities formed by geological processes in the volcanic rock, opening as south-facing shelters that look out over the basin.<\/p>\n
In the Pleistocene, they would have overlooked a lake ecosystem \u2014 water, aquatic birds, fish, and the plants and animals that concentrate wherever reliable water exists in an otherwise arid landscape.<\/p>\n
<\/p>\n
For people moving through the northern Great Basin approximately 14,000 years ago, this combination would have been highly attractive.<\/p>\n
A south-facing cave above a lake provides shelter, warmth in winter, a commanding view of the surrounding terrain, and proximity to the diverse resources of a lake-edge environment.<\/p>\n
The caves are not hidden or inaccessible; they sit in a position that any competent land-reading person moving through the basin would recognize as valuable.<\/p>\n
The caves have multiple chambers and alcoves \u2014 sufficient to shelter small groups, to store materials, to provide a semi-permanent habitation site that people could return to across seasons.<\/p>\n
The sediment that has accumulated on the cave floors over thousands of years preserves not just the artifacts that people left behind but the organic residues of daily life: food processing, fire use, sleep, and \u2014 critically for the Paisley story \u2014 biological waste.<\/p>\n
<\/p>\n
The preservation conditions in the caves are what made the coprolite evidence possible.<\/p>\n
Caves provide several preservation advantages over open-air sites.<\/p>\n
They protect organic material from the direct weathering of precipitation and sunlight.<\/p>\n
The alkaline chemistry of the volcanic and carbonate sediments in many cave environments inhibits the microbial decomposition that would destroy organic materials in more chemically active soils.<\/p>\n
And the consistently dry conditions of the Great Basin interior \u2014 even though the regional climate was wetter during the late Pleistocene than today \u2014 helped maintain the desiccation that is one of the most important factors in the preservation of both the coprolites and their organic contents.<\/p>\n
This preservation context is worth dwelling on, because it explains something about why the Paisley evidence takes the specific form that it does.<\/p>\n
<\/p>\n
Skeletal material from the relevant period, in this part of North America, is extraordinarily rare.<\/p>\n
The Great Basin environment, while preserving some categories of organic material very well, is not consistently favorable for bone preservation.<\/p>\n
The Paisley caves did not produce a human skeleton from 14,000 years ago.<\/p>\n
What they produced was something far more humble but, in the specific questions it could address, surprisingly informative.<\/p>\n
Long Before the DNA Laboratory<\/p>\n
The history of archaeological attention to the Paisley Caves stretches back well before the era of ancient DNA analysis.<\/p>\n
Luther Cressman, the prominent Oregon archaeologist often described as the father of Oregon archaeology, conducted excavations at Paisley Caves beginning in the 1930s.<\/p>\n
<\/p>\n
Cressman was a systematic and productive researcher who worked across a wide range of Great Basin sites, documenting the archaeological record of a region that had received little systematic attention before his work.<\/p>\n
Cressman recovered evidence of human occupation at the Paisley Caves from layers that he and his colleagues argued were geologically old.<\/p>\n
He found artifacts and other evidence of human presence, and he argued that some of this evidence was from the Pleistocene period \u2014 a claim that, in the academic climate of the mid-twentieth century, was viewed with considerable caution by many of his colleagues in the field.<\/p>\n
The specific nature of the evidence Cressman found, and the arguments he made about its age, are worth understanding as context for the later DNA research.<\/p>\n
<\/p>\n
The Great Basin archaeological record from this period includes a range of evidence \u2014 stone tools, fire-cracked rock, plant processing debris, and occasional faunal remains \u2014 that collectively suggests human occupation of the region extends well back into the late Pleistocene.<\/p>\n
But establishing the specific age and cultural affiliation of this evidence, in a region where the sediment record can be complex and where many of the most diagnostic artifact types are similar across long time periods, has always been challenging.<\/p>\n
The caves received additional archaeological attention in the years and decades following Cressman’s work.<\/p>\n
Dennis Jenkins of the University of Oregon Museum of Natural and Cultural History led the excavations that produced the coprolite evidence reported in 2008, building on the site’s earlier archaeological history and applying the more sophisticated dating and analytical methods that had become available by the late twentieth and early twenty-first centuries.<\/p>\n
Jenkins and his team excavated with careful attention to stratigraphic context \u2014 the vertical sequence of sediment layers that records the accumulation of material over time.<\/p>\n
<\/p>\n
Documenting stratigraphy carefully is essential in any archaeological excavation, but it is particularly important in caves, where the complexity of depositional processes \u2014 including both natural accumulation of windblown sediment and the activities of both humans and animals \u2014 can create situations where materials from different time periods end up in the same layer, or where materials from one layer get displaced into another through processes that can be difficult to identify without careful observation.<\/p>\n
The Jenkins excavations documented multiple stratigraphic layers at the caves, each with its own character and associated materials.<\/p>\n
The deepest layers \u2014 the ones most relevant to the pre-Clovis question \u2014 were the focus of the most intense analytical attention after the initial DNA results were obtained.<\/p>\n
What a Coprolite Can Tell You<\/p>\n
The word “coprolite” comes from Greek roots meaning “dung stone,” and while the colloquial description of these objects is inevitable, it tends to obscure how scientifically remarkable they can be as archaeological specimens.<\/p>\n
A coprolite is not simply old feces.<\/p>\n
<\/p>\n
It is a biological time capsule.<\/p>\n
When biological waste desiccates rapidly and is subsequently buried in dry, stable sediment, it can preserve an extraordinary range of information about the organism that produced it and about the environment in which that organism was living.<\/p>\n
Food remains are among the most commonly preserved contents of coprolites.<\/p>\n
The hard parts of plant foods \u2014 seed coats, pollen grains, plant phytoliths \u2014 survive desiccation far better than soft tissue, and their presence in a coprolite can identify specific plant foods consumed by the producer.<\/p>\n
The bones and scales of fish, the hair of mammals, and the hard parts of invertebrates can also survive in coprolites and identify dietary items.<\/p>\n
<\/p>\n
For archaeologists interested in understanding what people ate, how they processed their food, and what plant and animal resources they were exploiting in a specific time and place, a directly dated coprolite is a uniquely informative specimen.<\/p>\n
Parasites are another category of preserved content.<\/p>\n
The eggs of intestinal parasites \u2014 roundworms, hookworms, and other helminths \u2014 are remarkably resistant to decay and can survive in coprolites for thousands of years.<\/p>\n
The presence of specific parasite species in a coprolite can reveal something about the general health status of the producing population and, in some cases, about the geographic origins of those people, since different human populations carried different parasite assemblages depending on the specific environments they had inhabited.<\/p>\n
Pollen preserved in coprolites documents the plants that were seasonally active in the environment when the feces were deposited \u2014 contributing to paleoecological reconstruction and, in some cases, helping to confirm the season during which a site was occupied.<\/p>\n
<\/p>\n
And, crucially for the Paisley story, coprolites can preserve DNA.<\/p>\n
The cells that line the digestive tract are shed continuously during the passage of food, and some of these cells become incorporated into feces as it moves through the intestine.<\/p>\n
These cells carry DNA, and in conditions of rapid desiccation and cool, stable burial, that DNA can be preserved for thousands of years \u2014 degraded, fragmented, but potentially extractable and analyzable using the methods of ancient DNA research.<\/p>\n
The direct radiocarbon dating of coprolites is another significant advantage.<\/p>\n
<\/p>\n
Coprolites are composed of organic material, and the carbon in that material can be dated directly by radiocarbon methods.<\/p>\n
Unlike dating the context around a stone tool \u2014 where the tool itself is not datable and the surrounding sediment may have complex relationships to when the tool was deposited \u2014 dating a coprolite directly produces an age for the organic material itself.<\/p>\n
If that material contains human DNA, the combination of a direct date and a biological identification is extraordinarily powerful evidence.<\/p>\n
The Paisley coprolites offered exactly this combination.<\/p>\n
<\/p>\n
But extracting reliable information from each line of evidence proved more complicated than it initially appeared.<\/p>\n
The 2008 Discovery and What It Claimed<\/p>\n
The 2008 paper by M.<\/p>\n
Thomas P.<\/p>\n
Gilbert and colleagues, published in Science, reported results from the analysis of coprolites recovered from Paisley Caves during the Jenkins excavations.<\/p>\n
The paper focused specifically on specimens from the deepest layers of the site \u2014 layers that Jenkins and his team believed, based on stratigraphic analysis and associated radiocarbon dates, to represent occupation during the late Pleistocene.<\/p>\n
The analytical work was conducted at multiple independent ancient DNA laboratories \u2014 a methodological precaution designed to reduce the risk of contamination and to allow cross-checking of results.<\/p>\n
<\/p>\n
Ancient DNA analysis requires working in environments that are as free as possible from modern human DNA, which is present essentially everywhere that human beings work and live.<\/p>\n
Any lapse in contamination control risks introducing modern sequences into the analysis that could be mistaken for authentic ancient sequences.<\/p>\n
The results were significant.<\/p>\n
Mitochondrial DNA was recovered from multiple coprolite specimens.<\/p>\n
The sequences identified belonged to haplogroups that are recognized as Native American founding lineages \u2014 specifically haplogroup A2 and haplogroup B2, which are among the maternal lineages that trace their origin to the ancestral populations that crossed into the Americas from northeastern Asia through Beringia.<\/p>\n
The radiocarbon dates associated with the human-positive coprolites placed some specimens at ages that, when calibrated to calendar years, fell in the range of approximately 14,200 to 14,300 years before present.<\/p>\n
<\/p>\n
The specific dates reported in the paper were expressed in radiocarbon years before present, and the conversion to calibrated calendar years requires application of calibration curves that account for the known variations in atmospheric radiocarbon concentration over time.<\/p>\n
The calibrated range placed the specimens roughly 1,000 or more radiocarbon years before the conventional Clovis horizon.<\/p>\n
The combination \u2014 human mitochondrial DNA, directly dated to before Clovis \u2014 was, as the paper’s authors understood, a remarkable result.<\/p>\n
It placed people in the Oregon Great Basin at a time when, according to the Clovis-first model that had dominated North American archaeology for decades, humans were not yet supposed to be there.<\/p>\n
The paper was careful in its framing.<\/p>\n
<\/p>\n
The authors acknowledged the limitations of mitochondrial DNA analysis \u2014 specifically, that mitochondrial DNA establishes maternal lineage but does not provide a complete picture of biological ancestry, does not identify individuals, and cannot establish cultural affiliation with any specific modern community.<\/p>\n
They acknowledged that the coprolite identification was based on a combination of physical morphology, dietary content, and the DNA results themselves.<\/p>\n
They acknowledged that contamination was an ever-present concern in ancient DNA work and described the precautions taken.<\/p>\n
But the headline result was impossible to misunderstand: human DNA in directly dated coprolites from a layer older than Clovis, from the Oregon Great Basin.<\/p>\n
What Haplogroups A2 and B2 Actually Mean<\/p>\n
<\/p>\n
The mitochondrial haplogroups identified in the Paisley coprolites \u2014 A2 and B2 \u2014 are part of a classification system that organizes the diversity of human mitochondrial DNA into related groups based on shared mutations.<\/p>\n
Mitochondrial DNA is inherited exclusively through the maternal line.<\/p>\n
Unlike the nuclear DNA that we inherit from both parents, mitochondrial DNA is passed from mother to child without recombination \u2014 it is a direct copy, with only rare mutations accumulating over time.<\/p>\n
This makes mitochondrial DNA a powerful tool for tracing maternal lineage over many generations.<\/p>\n
Haplogroups are defined by specific sets of mutations that accumulated in ancestral mitochondrial genomes at specific points in human prehistory.<\/p>\n
If two individuals share the same haplogroup, they share a common maternal ancestor at some point in the past \u2014 potentially very distant, but documentably connected through the unbroken maternal line.<\/p>\n
<\/p>\n
The haplogroups found in Native American populations trace their origin to northeastern Asian populations.<\/p>\n
The founding Native American haplogroups \u2014 labeled A, B, C, D, and X, with various subcategories including A2 and B2 \u2014 are found almost exclusively in Indigenous peoples of the Americas and in specific northeastern Asian populations that are most closely related to the founding Beringian population.<\/p>\n
The presence of haplogroup A2 and B2 sequences in the Paisley coprolites indicated that the individuals who produced those specimens had maternal ancestry traceable to the same founding lineages as modern Native American peoples.<\/p>\n
This finding was significant because it established a biological connection between the ancient coprolite producers and the Indigenous people of the Americas \u2014 not a connection to European populations, not a connection to African populations, not a connection to Asian populations in general, but specifically to the founding lineages of Native America.<\/p>\n
<\/p>\n
It is important, however, to be precise about what mitochondrial haplogroup identification does and does not establish.<\/p>\n
A haplogroup is not a complete genetic portrait of an individual.<\/p>\n
It reflects only the maternal lineage \u2014 one thread in the complex tapestry of an individual’s ancestry.<\/p>\n
Two people can share a haplogroup and be only distantly related through their maternal lines, while having very different ancestry on their paternal sides and through all the other lineages that contribute to their genetic composition.<\/p>\n
Haplogroup identification also does not establish a specific cultural, linguistic, or tribal identity.<\/p>\n
<\/p>\n
The founding Native American haplogroups were established in the ancestral Beringian population before the dispersal into the Americas, and they have been carried by the descendants of that founding population through thousands of years of population differentiation, cultural diversification, and geographic spread.<\/p>\n
Knowing that a 14,000-year-old individual had mitochondrial haplogroup A2 tells us something important about their ancestry.<\/p>\n
It does not tell us which language their descendants spoke, which cultural traditions they maintained, or which modern tribal nations are most directly descended from their specific community.<\/p>\n
These distinctions matter, and any responsible presentation of the Paisley evidence has to maintain them.<\/p>\n
Why the Timing Was Extraordinary<\/p>\n
<\/p>\n
The 2008 Paisley result arrived in a specific intellectual context that made it explosive, and that context needs to be understood to appreciate why the claim generated such intense scrutiny.<\/p>\n
The Clovis-first model \u2014 the hypothesis that the Clovis culture represented the first human presence in the Americas, and that all Native Americans descended from a single founding Clovis-era population \u2014 had been the dominant paradigm in North American archaeology for roughly fifty years by the time the Paisley results were published.<\/p>\n
It was not merely an academic hypothesis; it was a deeply entrenched framework that had shaped how archaeologists evaluated evidence, trained students, allocated research resources, and interpreted the significance of new findings.<\/p>\n
Under the Clovis-first model, any site claiming to show human presence before the Clovis horizon faced an extraordinarily high evidentiary bar.<\/p>\n
<\/p>\n
The model’s defenders were not simply being conservative \u2014 they had genuine reasons for their skepticism.<\/p>\n
A long history of spectacular pre-Clovis claims had preceded Paisley, and many of those claims had eventually been undermined by methodological problems: contaminated radiocarbon samples, natural processes that mimicked human artifact production, stratigraphic mixing that placed materials from different periods in the same layers, or simply the overenthusiastic interpretation of ambiguous evidence.<\/p>\n
The accumulated experience of seeing dramatic pre-Clovis claims collapse under scrutiny had made many researchers in the field reflexively suspicious of new ones.<\/p>\n
This was not unreasonable caution \u2014 it was calibrated skepticism based on a pattern that genuinely existed.<\/p>\n
<\/p>\n
The track record of pre-Clovis claims, through the middle of the twentieth century and into the later decades, was not encouraging.<\/p>\n
By 2008, however, the Clovis-first model was already under pressure from multiple directions.<\/p>\n
Monte Verde in southern Chile \u2014 a site with compelling evidence for human presence approximately 14,500 years ago, verified by independent researchers \u2014 had by then been accepted as a genuine pre-Clovis site by most specialists, though some holdouts remained.<\/p>\n
The geographic argument was damning: if people were at the southern tip of South America 14,500 years ago, they must have entered the Americas before that \u2014 probably well before \u2014 to have had time to travel that far from the entry point in Beringia.<\/p>\n
The Clovis-first model had been weakening for years before Paisley was published.<\/p>\n
<\/p>\n
What the Paisley result did was add another line of evidence from a different geographic region, with a different type of evidence \u2014 ancient DNA in directly dated biological material \u2014 pointing toward the same conclusion that Monte Verde and other sites had been suggesting: the Americas were inhabited before Clovis.<\/p>\n
But the specific nature of the Paisley evidence \u2014 ancient DNA analysis, a technique with specific vulnerabilities to contamination and misinterpretation \u2014 made the result particularly easy to attack on methodological grounds.<\/p>\n
And the critics who attacked it were not wrong to do so.<\/p>\n
The First Wave of Doubt<\/p>\n
The published criticism of the 2008 Paisley paper appeared in Science in 2009, from two groups of researchers who raised specific, technical objections that could not be dismissed.<\/p>\n
Hendrik Poinar and colleagues identified several concerns about the evidence’s reliability.<\/p>\n
<\/p>\n
Their most significant objection was about DNA movement through sediment \u2014 the possibility that human DNA from later layers could have migrated downward through the cave sediment and become incorporated into older coprolites, making the ancient specimens appear to contain human DNA that was not present when the coprolites were originally deposited.<\/p>\n
This is not a hypothetical concern invented to oppose unwelcome results.<\/p>\n
It is a genuine phenomenon documented in multiple archaeological contexts.<\/p>\n
DNA can move through sediment in several ways.<\/p>\n
It can be carried by percolating water, which transports dissolved organic material downward through sediment profiles.<\/p>\n
It can be carried by organic particles that are physically transported during periods when the sediment is disturbed or when the cave floor is wetted and dries.<\/p>\n
And it can be transported by fungal networks \u2014 the mycelia that thread through soil and sediment can take up DNA from the environment and spread it horizontally and vertically in ways that bear no relationship to the original depositional context.<\/p>\n
<\/p>\n
The specific concern at Paisley was that if the cave had been occupied by people at multiple time periods \u2014 which it clearly had been, given the archaeological evidence from multiple sediment layers \u2014 then DNA from more recent occupants could potentially have moved downward through the sediment and contaminated the older layers.<\/p>\n
The coprolites from the oldest layers, lying in sediment that also contained DNA from later periods of occupation, might have absorbed some of that later DNA, making ancient non-human coprolites appear to contain human sequences.<\/p>\n
This concern was sharpened by a second category of objection: the question of whether the coprolites identified as human were in fact human.<\/p>\n
Coprolite identification is not always straightforward.<\/p>\n
Human feces and the feces of other omnivorous mammals can be morphologically similar, particularly after thousands of years of desiccation and mineralization have altered their original character.<\/p>\n
<\/p>\n
Chemical analysis of the coprolites’ composition was needed to confirm that the specimens containing human DNA had actually been produced by humans rather than by another mammal that had subsequently been exposed to environmental human DNA.<\/p>\n
Paul Goldberg and colleagues raised a third category of concern: the stratigraphic integrity of the cave deposits.<\/p>\n
If the sediment layers at Paisley had been disturbed by natural processes \u2014 frost heaving, bioturbation by burrowing animals, the activities of carnivores, or water movement \u2014 then materials from different time periods could have been mixed into the same apparent layer.<\/p>\n
The radiocarbon dates associated with a specific layer might not accurately reflect the age of all the materials in that layer.<\/p>\n
The stratigraphy of caves is inherently complex.<\/p>\n
<\/p>\n
Caves are not simply filled gradually from bottom to top as sediment accumulates.<\/p>\n
They are dynamic environments in which sediment is deposited, eroded, and redeposited; in which the activities of animals can create complex mixing of materials; and in which the physical structure of the cave itself \u2014 overhanging walls, alcoves, irregularities in the floor \u2014 creates microenvironments with different depositional histories.<\/p>\n
These were not frivolous objections.<\/p>\n
They identified genuine vulnerabilities in the original evidence that needed to be addressed.<\/p>\n
The question was whether the Paisley evidence could survive them.<\/p>\n
<\/p>\n
How DNA Moves Through the Ground<\/p>\n
Understanding why the DNA movement concern was taken so seriously requires a brief explanation of how organic material behaves in sediment \u2014 something that has become much better understood in the decades since ancient DNA analysis became a standard archaeological tool.<\/p>\n
Sediment is not an inert storage medium.<\/p>\n
It is a complex chemical and biological environment in which organic molecules are constantly being transformed by chemical reactions, consumed and transported by microorganisms, and physically moved by water and other agents.<\/p>\n
The assumption that organic material stays precisely where it was deposited \u2014 that the carbon, nitrogen, and other elements in an ancient coprolite are the same carbon and nitrogen that entered the sediment when the feces were originally deposited \u2014 is often an approximation that must be carefully evaluated.<\/p>\n
<\/p>\n
The DNA concern is particularly acute because DNA is not simply a passive molecule embedded in a fixed structure.<\/p>\n
When organisms die and their tissues decompose, the DNA they contained is released into the surrounding environment.<\/p>\n
In soil and sediment, this environmental DNA \u2014 sometimes called eDNA \u2014 can persist for varying periods depending on temperature, pH, and the presence of protective mineral surfaces that can shield DNA molecules from enzymatic degradation.<\/p>\n
Environmental DNA in sediment can be transported by percolating water.<\/p>\n
As rainwater or snowmelt moves downward through a sediment profile, it carries dissolved and suspended organic material \u2014 including DNA fragments \u2014 with it.<\/p>\n
<\/p>\n
This downward transport can result in DNA from surface or near-surface environments contaminating deeper, older sediment layers.<\/p>\n
The phenomenon is well-documented and is a recognized source of error in the analysis of sediment cores for ancient DNA.<\/p>\n
The specific application to Paisley is straightforward to state: if the cave floor had been occupied at multiple time periods, human DNA from more recent occupants would be present in the sediment of the upper layers.<\/p>\n
If water had percolated through those upper layers and carried human DNA downward, it could have reached the older, deeper layers where the pre-Clovis coprolites were located.<\/p>\n
Those coprolites, lying in sediment enriched with environmental human DNA, could have absorbed that DNA \u2014 creating the appearance of ancient human sequences in specimens that might actually have been produced by non-human mammals.<\/p>\n
<\/p>\n
The response to this concern required demonstrating that the DNA found in the Paisley coprolites was genuinely ancient \u2014 that it showed the chemical characteristics of aged material rather than fresh contamination \u2014 and that the coprolites themselves were genuinely human rather than non-human specimens that had absorbed environmental human DNA.<\/p>\n
Ancient DNA has specific chemical signatures that distinguish it from modern DNA.<\/p>\n
The most important is a pattern of chemical damage called cytosine deamination, in which cytosine bases at the ends of DNA fragments are chemically modified to uracil.<\/p>\n
This damage pattern accumulates predictably with time and is present in genuinely ancient sequences but not in modern contamination.<\/p>\n
Demonstrating this damage pattern in the Paisley coprolite sequences was one way to establish that the DNA was genuinely ancient rather than modern contamination.<\/p>\n
But even ancient DNA could potentially have moved through the sediment from more recent ancient layers rather than from the very oldest ones.<\/p>\n
<\/p>\n
Addressing this concern required additional evidence \u2014 specifically, evidence that the coprolites themselves were human, not just evidence that the DNA in them was genuinely old.<\/p>\n
The Coprolite Identity Problem<\/p>\n
The identification of a coprolite as human is not as simple as it might initially appear.<\/p>\n
Dried feces from different species can be surprisingly similar in gross morphology, particularly after the taphonomic processes of desiccation, compaction, and mineralization have modified their original character.<\/p>\n
And in a cave that has been used by multiple species \u2014 humans, carnivores, rodents, and other animals \u2014 over thousands of years, the coprolites from different producers will all be mixed together in the same sediment.<\/p>\n
The 2008 paper had relied on a combination of morphological assessment (the physical characteristics of the coprolites, including their shape, size, and apparent internal structure), dietary content (the types of food remains identifiable within the specimens), and the DNA results themselves to identify specific specimens as human.<\/p>\n
<\/p>\n
Critics argued that this combination was insufficient \u2014 that morphology alone is unreliable for distinguishing human from non-human coprolites, and that using DNA evidence to support the identification of specimens whose DNA was itself the main evidence being presented created a circular argument.<\/p>\n
What was needed was an independent line of evidence that could confirm the human origin of the coprolites without relying on the DNA results.<\/p>\n
The answer, which would not arrive until 2020, was fecal lipid biomarkers.<\/p>\n
Fecal lipid biomarkers are specific compounds produced during the metabolism of cholesterol and other sterols in the digestive system.<\/p>\n
Different species of mammals have different sterol metabolic pathways, and the specific compounds they produce in their intestines \u2014 and subsequently excrete \u2014 differ in ways that can be identified by chemical analysis even after thousands of years in the archaeological record.<\/p>\n
The most important distinction is between the fecal biomarker profile of humans and the fecal biomarker profile of other mammals.<\/p>\n
<\/p>\n
Human intestinal bacteria transform dietary cholesterol into specific compounds, including coprostanol and its related molecules, through a well-characterized metabolic pathway.<\/p>\n
While other mammals also produce fecal sterols, the specific ratios and the specific compounds produced by different species differ in ways that can be used to distinguish human from non-human fecal material.<\/p>\n
This approach is fundamentally independent of DNA analysis.<\/p>\n
It addresses the question “was this coprolite produced by a human or a non-human animal?” through a biochemical route that does not rely on the sequence of the DNA found in the specimen.<\/p>\n
If the lipid biomarker analysis identifies a coprolite as human, and the DNA analysis independently identifies human DNA in the same specimen, the two lines of evidence are mutually reinforcing in a way that neither could be alone.<\/p>\n
<\/p>\n
The 2020 study by Sistiaga and colleagues applied fecal lipid biomarker analysis to the Paisley coprolites.<\/p>\n
The results confirmed that three pre-Clovis coprolites showed biomarker profiles consistent with human origin.<\/p>\n
This was a genuinely significant contribution \u2014 it addressed one of the central criticisms of the 2008 paper through a method that the original criticism could not have anticipated.<\/p>\n
But the 2020 paper also addressed the DNA movement concern in a way that was more candid than the 2008 paper had been: the authors acknowledged that DNA movement through the sediment was a real phenomenon that could not be ruled out for all specimens, and that the biomarker evidence was valuable precisely because it could establish human origin independently of the DNA evidence.<\/p>\n
This was not a concession that the original DNA evidence was fraudulent \u2014 it was an honest acknowledgment that the DNA evidence alone had been insufficient to answer the coprolite identity question, and that the biomarker evidence was filling that gap.<\/p>\n
<\/p>\n
The Stratigraphy Problem in Detail<\/p>\n
The criticism of the cave’s stratigraphic integrity \u2014 the concern that the sediment layers might not represent a reliable record of the chronological sequence of human occupation \u2014 was among the more complex challenges facing the Paisley evidence, and addressing it required the most sustained and detailed archaeological response.<\/p>\n
Stratigraphic analysis is the foundation of archaeological dating.<\/p>\n
The principle of superposition \u2014 the observation that in an undisturbed sediment sequence, older materials are below younger materials \u2014 allows archaeologists to establish relative chronologies from the vertical position of materials in a site.<\/p>\n
When that principle is violated by natural or human disturbance, the relative chronology becomes unreliable, and radiocarbon dates associated with a disturbed layer may not accurately reflect the age of all the materials in that layer.<\/p>\n
<\/p>\n
In caves, multiple processes can disturb stratigraphic integrity.<\/p>\n
Frost heaving \u2014 the movement of sediment particles caused by the expansion of water as it freezes \u2014 can displace materials vertically, moving older objects upward and newer objects downward in ways that confound the expected stratigraphic sequence.<\/p>\n
Burrowing animals \u2014 rodents, in particular \u2014 create tunnels through sediment that mix materials from different layers.<\/p>\n
Carnivores occupying caves as dens carry material in and out and may rearrange existing deposits.<\/p>\n
Water infiltration through the cave ceiling or walls can transport materials both horizontally and vertically.<\/p>\n
<\/p>\n
And human occupation itself \u2014 digging hearths, creating storage features, or simply walking across a sediment surface \u2014 can disturb earlier deposits.<\/p>\n
The Goldberg et al. critique specifically raised concerns about whether the cave sediments at Paisley showed evidence of the kinds of disturbance that could undermine the stratigraphic integrity of the pre-Clovis layers.<\/p>\n
The concerns were not without basis \u2014 cave sediments routinely show evidence of multiple types of disturbance, and the complexity of cave depositional processes means that even careful excavation and documentation may not capture all the nuances of how a specific layer formed and was subsequently modified.<\/p>\n
Addressing these concerns required more than asserting that the original excavation had been careful.<\/p>\n
<\/p>\n
It required going back to the site, conducting additional excavation with even more rigorous stratigraphic documentation, collecting a much denser set of radiocarbon dates from materials distributed throughout the sediment sequence, and applying detailed micromorphological analysis \u2014 the examination of thin sections of sediment under a microscope \u2014 to characterize the depositional processes that had formed each layer.<\/p>\n
This is exactly what the research team did.<\/p>\n
Going Back Into the Caves<\/p>\n
The renewed excavation at Paisley Caves, reported in the 2012 Jenkins et al. paper in Science, was a systematic response to the specific criticisms that had been raised about the 2008 evidence.<\/p>\n
Rather than simply asserting that the original work had been correct, the researchers returned to the site with a research design specifically intended to address each category of concern.<\/p>\n
The 2012 excavations were more extensive than the original work, opening larger areas of the cave floor and documenting the stratigraphy in greater detail.<\/p>\n
<\/p>\n
The documentation included both standard archaeological recording methods \u2014 measured profile drawings, detailed written descriptions of each sediment layer \u2014 and micromorphological sampling, in which blocks of undisturbed sediment were removed intact, hardened with resin, sectioned into thin slices, and examined under microscopes in a laboratory.<\/p>\n
Micromorphology allows archaeologists to see the detailed structure of sediment at a scale that is invisible to the naked eye \u2014 the arrangement of particles, the presence of biological remains, the chemical stains that indicate past processes \u2014 and to characterize the specific events that formed each layer.<\/p>\n
The radiocarbon dating program was dramatically expanded.<\/p>\n
The 2008 paper had relied on a relatively small number of radiocarbon dates to establish the age of the pre-Clovis layers.<\/p>\n
The 2012 program added many more dates, from a wider range of materials distributed throughout the sediment sequence.<\/p>\n
<\/p>\n
This dense dating program served several purposes: it allowed researchers to identify any inconsistencies in the stratigraphic sequence (dates that were in the wrong order relative to their stratigraphic position would indicate disturbance), it provided much stronger statistical confidence in the age estimates for specific layers, and it extended the chronological documentation of the site to cover periods both before and after the pre-Clovis deposits, providing context for interpreting the oldest evidence.<\/p>\n
The independent testing component of the 2012 research was particularly important.<\/p>\n
The original coprolite DNA analysis had been conducted at specific laboratories.<\/p>\n
For the 2012 paper, additional coprolite specimens were analyzed at different, independent laboratories whose personnel did not know the stratigraphic context or the results of the original analysis \u2014 a “blind” test designed to prevent any inadvertent bias in the results.<\/p>\n
If the original DNA results were genuine and reproducible, independent laboratories analyzing different specimens from the same context should obtain similar results.<\/p>\n
<\/p>\n
If the results were artifacts of contamination at specific laboratories or of some other systematic error, independent analysis should produce different results.<\/p>\n
The results of the independent testing were consistent with the original findings.<\/p>\n
Human mitochondrial DNA was again identified in coprolites from the pre-Clovis layers, and the haplogroups identified were again consistent with Native American founding lineages.<\/p>\n
This consistency across independent laboratories, analyzing different specimens from the same context, substantially strengthened the credibility of the DNA evidence.<\/p>\n
The 2012 paper also reported the discovery of artifacts that added an important new dimension to the Paisley evidence.<\/p>\n
Western Stemmed Points and the Technology Question<\/p>\n
<\/p>\n
One of the significant findings reported in the 2012 Jenkins et al. paper was the recovery of stone artifacts from contexts contemporaneous with or older than Clovis technology in western North America.<\/p>\n
Specifically, the paper reported Western Stemmed projectile points from the Paisley Caves.<\/p>\n
Western Stemmed technology is a broad category of stone point production that includes a range of point types with a distinctive design feature: a narrowed stem at the base of the point that facilitates hafting to a wooden or bone shaft.<\/p>\n
The stem contrasts with the concave base of Clovis points, which are thinned through the distinctive fluting process, and with other hafting solutions used by contemporary or later cultures.<\/p>\n
Western Stemmed technology appears across a wide geographic range in the western United States and has been documented from multiple sites in the Great Basin, the Columbia Plateau, and surrounding regions.<\/p>\n
<\/p>\n
The 2012 Paisley paper argued that the Western Stemmed points from the caves were found in contexts demonstrating that this technology was present in the region at least as early as Clovis \u2014 and possibly earlier, depending on how the specific dates were interpreted.<\/p>\n
The significance of this finding for the broader debate about the peopling of the Americas was considerable.<\/p>\n
If Clovis technology had been the first technology to spread across the Americas \u2014 as the Clovis-first model implied \u2014 then Western Stemmed technology should either postdate Clovis or derive from it.<\/p>\n
The Paisley evidence suggested instead that Western Stemmed technology was contemporaneous with Clovis in at least some regions of the Far West, and that the two technological traditions might have developed in parallel rather than in a simple linear succession from one to the other.<\/p>\n
This parallel development hypothesis had significant implications for models of the initial American dispersal.<\/p>\n
<\/p>\n
If there were multiple technological traditions present in the Americas at roughly the same time, it suggests either that there were multiple founding populations that developed different technologies, or that a single founding population rapidly differentiated into regional technological traditions as it spread through different environments.<\/p>\n
The Paisley evidence alone could not distinguish between these possibilities, but it added to a growing body of evidence suggesting that the early archaeological record of the Americas was more complex than the Clovis-first model had allowed for.<\/p>\n
Critically, the 2012 paper also noted the absence of diagnostic Clovis technology from the Paisley Caves assemblage.<\/p>\n
The caves did not contain the distinctive fluted Clovis points that would be expected if the site’s occupants were part of the Clovis cultural tradition.<\/p>\n
This absence \u2014 which is never straightforward to interpret, since the absence of specific artifacts can reflect sampling bias, functional specialization, or genuine cultural difference \u2014 was argued by the authors to support the interpretation that the Paisley people were not Clovis but instead were part of a separate technological tradition that was present in the Far West at or before the time of the Clovis expansion.<\/p>\n
<\/p>\n
The Expanded Radiocarbon Program and What It Showed<\/p>\n
The dense radiocarbon dating program reported in the 2012 paper is worth examining in some detail, because it illustrates how the approach to establishing the age of the Paisley evidence was fundamentally different from the approach used in the 2008 paper.<\/p>\n
The 2008 paper relied primarily on direct radiocarbon dates from the coprolites themselves.<\/p>\n
This approach has obvious appeal \u2014 dating the specimens directly is more powerful than dating associated materials whose relationship to the specimens might be questioned.<\/p>\n
But direct dating of a small number of specimens, without broader chronological context from the surrounding sediment, is vulnerable to the objection that the dated specimens might not be representative of their apparent stratigraphic context.<\/p>\n
<\/p>\n
The 2012 program addressed this vulnerability by establishing what archaeologists sometimes call a “radiocarbon chronological framework” \u2014 a network of dates from multiple different types of material distributed throughout the site’s stratigraphic sequence.<\/p>\n
This network included dates from plant materials, animal bones, charcoal from hearths, and the coprolites themselves, distributed across multiple different excavation areas and multiple different stratigraphic layers.<\/p>\n
When a dense network of dates is consistent with the expected stratigraphic sequence \u2014 when older layers consistently produce older dates and younger layers consistently produce younger dates, without anomalies that would indicate mixing \u2014 it provides much stronger evidence for the integrity of the stratigraphy than any single date could provide.<\/p>\n
And when specific specimens \u2014 like the pre-Clovis coprolites \u2014 produce dates consistent with the broader network of dates from the same layer, the case that those specimens are genuinely from that layer becomes much more robust.<\/p>\n
<\/p>\n
The 2012 radiocarbon program produced results that were broadly consistent with the stratigraphic sequence documented by the excavations.<\/p>\n
The pre-Clovis layers produced dates in the expected range.<\/p>\n
The dates from materials throughout the sequence were consistent with the stratigraphic positions of those materials.<\/p>\n
The anomalies that would indicate major stratigraphic mixing \u2014 dates in the wrong order relative to their position, or dates that were wildly inconsistent with the surrounding materials \u2014 were not apparent.<\/p>\n
This does not prove that every coprolite in the oldest layers was exactly where it was originally deposited, or that no DNA movement through sediment had occurred at all.<\/p>\n
It does substantially strengthen the case that the stratigraphic integrity of the site was sufficient to support the interpretation that the pre-Clovis materials were genuinely from the period indicated by the dates.<\/p>\n
<\/p>\n
The Second Opening: The Fecal Lipid Biomarkers<\/p>\n
The 2020 paper by Sistiaga and colleagues represents the most methodologically innovative contribution to the Paisley story, and it merits careful attention because of what it adds \u2014 and what it honestly acknowledges.<\/p>\n
The paper reported the application of fecal lipid biomarker analysis to Paisley coprolites.<\/p>\n
The specific biomarkers analyzed were fecal stanols \u2014 compounds produced by the bacterial reduction of sterols in the intestine, with different mammals producing different characteristic stanol profiles.<\/p>\n
The human-specific stanol profile \u2014 dominated by coprostanol, 5\u03b2-cholestan-3\u03b2-ol \u2014 is well-documented in fresh and ancient human fecal material and has been used extensively as a tracer for human sewage in environmental archaeology.<\/p>\n
<\/p>\n
The application to the Paisley coprolites required adapting methods developed primarily for environmental sample analysis to the challenge of identifying human fecal material within individual solid coprolite specimens from a specific archaeological context.<\/p>\n
This is analytically more demanding than identifying the presence of human-specific biomarkers in sediment cores or water samples, where the relevant compounds may be present in measurable quantities without the need to attribute them to specific discrete specimens.<\/p>\n
The 2020 analysis successfully identified three coprolites from the pre-Clovis layers of Paisley Caves as having fecal biomarker profiles consistent with human origin.<\/p>\n
The biomarker evidence was independent of the DNA evidence \u2014 it was produced by a fundamentally different biochemical pathway and analyzed through fundamentally different chemical methods.<\/p>\n
<\/p>\n
The two lines of evidence \u2014 human mitochondrial DNA and human-consistent fecal biomarkers \u2014 pointed to the same conclusion through independent routes.<\/p>\n
This convergence is exactly the kind of evidence that is most compelling in science.<\/p>\n
When two independent methods, using different types of data and different analytical techniques, produce results consistent with the same interpretation, the probability that both are artifacts of error or contamination decreases substantially.<\/p>\n
It is possible to imagine how contamination or other problems could produce a false positive in DNA analysis alone.<\/p>\n
It is possible to imagine how a coprolite misidentification could produce a false positive in DNA analysis.<\/p>\n
<\/p>\n
It is much more difficult to imagine how both the DNA evidence and the biomarker evidence could independently produce false positives pointing to the same conclusion.<\/p>\n
The 2020 paper was also honest about the limitations of the fecal biomarker evidence.<\/p>\n
The authors acknowledged that the preservation of biomarkers over thousands of years is not uniform and that some specimens may have lost their biomarker signal through degradation or contamination.<\/p>\n
They acknowledged that the distinction between human and some other omnivorous mammals in the fecal biomarker profile is not always perfectly sharp.<\/p>\n
And they acknowledged \u2014 importantly \u2014 that the question of whether DNA had moved through the Paisley sediments from younger to older contexts remained a concern that the biomarker evidence could not entirely resolve, since the biomarkers themselves could potentially be subject to some forms of post-depositional movement.<\/p>\n
<\/p>\n
This acknowledgment was not a concession of defeat.<\/p>\n
It was an honest characterization of the complexity of the evidence and the limits of what any single method can establish.<\/p>\n
What the fecal biomarker paper accomplished was not to make the Paisley evidence bulletproof \u2014 no evidence of this type ever is \u2014 but to add a powerful independent line of evidence that substantially strengthened the case while being transparent about its own limitations.<\/p>\n
The Fiber Artifact and Independent Temporal Anchors<\/p>\n
<\/p>\n
In addition to the coprolite evidence, the Paisley Caves have produced other materials that contribute to establishing the site’s occupation history.<\/p>\n
Among the most interesting is the evidence from directly dated fiber or organic artifacts recovered from the pre-Clovis layers.<\/p>\n
The recovery and dating of fiber artifacts \u2014 items made from plant fibers, such as basketry, cordage, or other woven materials \u2014 from archaeological contexts is rarely straightforward, because organic materials are among the most vulnerable to post-depositional contamination and degradation.<\/p>\n
But when fiber artifacts can be securely dated and their stratigraphic context established, they provide an independent temporal anchor for human occupation that is distinct from both the coprolite evidence and the lithic artifact evidence.<\/p>\n
The Paisley Caves produced evidence of twisted fiber \u2014 materials consistent with human-made cordage or basketry \u2014 from contexts that, based on stratigraphic position and associated radiocarbon dates, appeared to fall within the pre-Clovis or approximately Clovis-age portion of the site’s sequence.<\/p>\n
<\/p>\n
The direct dating of these materials contributed to the overall chronological framework for early occupation at the site.<\/p>\n
The significance of fiber artifacts in this context goes beyond the date alone.<\/p>\n
The manufacture of twisted fiber cordage is a cognitively and technically demanding craft that requires knowledge of appropriate plant materials, understanding of fiber preparation techniques, and the manual dexterity and patience to produce functional cordage.<\/p>\n
It is a craft associated with technologically sophisticated people \u2014 people who understood that binding, bundling, and constructing with flexible fiber materials extended their ability to accomplish tasks that could not be achieved with rigid materials like stone or bone.<\/p>\n
People who were making cordage 14,000 years ago in the Oregon Great Basin were not primitive opportunists barely surviving in a hostile landscape.<\/p>\n
<\/p>\n
They were skilled craftworkers with a comprehensive material toolkit, using the full range of available materials \u2014 stone, bone, fiber, and others \u2014 to meet the demands of daily life in a challenging but resource-rich environment.<\/p>\n
The Landscape and the People Who Used It<\/p>\n
The Great Basin of the late Pleistocene was not the barren landscape that the term “desert” might suggest to modern readers.<\/p>\n
The presence of Lake Chewaucan \u2014 and of dozens of other pluvial lakes across the basin \u2014 created a network of resource-rich environments embedded within an otherwise arid matrix.<\/p>\n
The lake edges provided water, aquatic birds, fish, and diverse plant communities.<\/p>\n
The upland areas between the lakes offered a different set of resources \u2014 seed-bearing plants, rodents, and periodically, larger game animals.<\/p>\n
<\/p>\n
People moving through this landscape were not moving through emptiness.<\/p>\n
They were moving through a known world \u2014 a world mapped in memory and transmitted through generations as knowledge of where reliable water could be found, where particular plant foods peaked in productivity in different seasons, where game animals could be reliably intercepted, and where shelter could be found against the cold and wind.<\/p>\n
The Paisley Caves would have been a known location in this mental landscape \u2014 a south-facing shelter above a lake, reliably present, reliably sheltered, reliably close to water.<\/p>\n
People who knew the landscape well would have known about these caves and returned to them.<\/p>\n
<\/p>\n
The multi-period occupation documented in the Paisley sediment record is consistent with a pattern of regular, repeated use of a known, valued location \u2014 not a random encounter with an unknown cave, but a deliberate visit to a place that had been part of the community’s knowledge for generations.<\/p>\n
The dietary content of the Paisley coprolites contributes to understanding what these people were eating and how they were exploiting the resources of the lake basin.<\/p>\n
The plant remains identifiable in the coprolites include species consistent with the Great Basin flora of the late Pleistocene.<\/p>\n
The presence of specific seed types and plant parts that require processing \u2014 grinding, soaking, or heating to be digestible \u2014 indicates that the Paisley people were not simply consuming raw plant foods but were applying the processing knowledge necessary to make otherwise indigestible or toxic plant materials edible.<\/p>\n
This processing knowledge is another form of technological sophistication that is easy to overlook in discussions focused on stone tools.<\/p>\n
<\/p>\n
The ability to identify, harvest, prepare, and store plant foods is a complex body of knowledge that takes years to develop and generations to transmit.<\/p>\n
The people at Paisley Caves 14,000 years ago were not surviving by luck; they were applying a comprehensive knowledge of the resources available in their environment and of the techniques required to exploit those resources effectively.<\/p>\n
Placing Paisley in the Broader Pre-Clovis Picture<\/p>\n
Paisley Caves does not stand alone in the evidence for pre-Clovis human presence in the Americas.<\/p>\n
It is one piece in a growing body of evidence from multiple sites across both continents that collectively indicates the Americas were inhabited before the Clovis horizon.<\/p>\n
<\/p>\n
The most securely dated and most widely accepted pre-Clovis site is Monte Verde in southern Chile, where direct radiocarbon dates on organic materials associated with human artifacts have consistently produced ages of approximately 14,500 calibrated years before present.<\/p>\n
The significance of this date is amplified by Monte Verde’s geographic location \u2014 at the southern tip of South America, far from any proposed point of entry into the Americas.<\/p>\n
For people to have been at Monte Verde 14,500 years ago, they must have entered the Americas considerably earlier, requiring enough time for a human population to disperse from the entry point in Beringia to the southern end of South America.<\/p>\n
Cooper’s Ferry in Idaho has produced lithic artifacts from a context that has been dated to approximately 15,000 years before present \u2014 older than Paisley, and farther north, closer to the proposed entry point.<\/p>\n
<\/p>\n
The technology at Cooper’s Ferry shows some similarities to technologies used in northeastern Asia during the same period, supporting the Beringian origin model for the first Americans.<\/p>\n
The Cooper’s Ferry evidence suggests that the initial dispersal into the Americas was underway by at least 15,000 years ago.<\/p>\n
The Manis mastodon site in Washington State produced evidence of a projectile point \u2014 made from the bone of a mastodon, a distinctive and technically demanding material \u2014 embedded in the rib of a mastodon that has been dated to approximately 13,800 calibrated years before present.<\/p>\n
This date places it somewhat before or contemporaneous with Clovis, and the embedded bone point indicates not just human presence but active, sophisticated hunting of very large animals.<\/p>\n
<\/p>\n
White Sands National Park in New Mexico has produced what may be the most striking recent addition to the pre-Clovis evidence: footprints \u2014 actual human footprints, preserved in ancient lake sediment \u2014 that have been dated by multiple methods, including the radiocarbon dating of seeds embedded in the sediment at the level of the footprints, to approximately 21,000 to 23,000 years before present.<\/p>\n
These dates, if sustained, would push the evidence for human presence in the Americas back substantially further than the Paisley evidence.<\/p>\n
The White Sands footprint dating has been questioned by some researchers on methodological grounds \u2014 concerns about the specific radiocarbon reservoir effects in ancient lake sediment \u2014 and the debate continues.<\/p>\n
And from the Yukon, Bluefish Caves has produced directly dated, human-modified animal bones at approximately 24,000 calibrated years before present \u2014 evidence, as discussed elsewhere in this series, of human presence in eastern Beringia during the Last Glacial Maximum.<\/p>\n
Paisley fits into this picture as a particularly well-documented piece of evidence with multiple independent lines of confirmation.<\/p>\n
<\/p>\n
It is not the oldest claim in the pre-Clovis literature, and it is not without its own remaining uncertainties.<\/p>\n
But the combination of directly dated coprolites, independent DNA testing, expanded radiocarbon chronology, associated artifacts, and fecal lipid biomarkers makes it among the most methodologically robust contributions to the pre-Clovis evidence base.<\/p>\n
Why the Critics Were Right to Ask<\/p>\n
It is tempting, in telling the story of how the Paisley evidence survived scientific scrutiny, to frame the critics as obstacles who tried and failed to undermine a discovery that was correct all along.<\/p>\n
That framing would be both unfair and misleading.<\/p>\n
<\/p>\n
The critics of the 2008 Paisley paper raised legitimate questions that the original evidence genuinely could not answer.<\/p>\n
The concerns about DNA movement through sediment were not invented \u2014 they were based on documented phenomena with real implications for the interpretation of the evidence.<\/p>\n
The concerns about coprolite identity were not pedantic \u2014 they identified a genuine gap in the evidentiary chain that needed to be filled.<\/p>\n
The concerns about stratigraphic integrity were not obstructionism \u2014 they reflected genuine knowledge of how caves work and how archaeological evidence can become unreliable through post-depositional processes.<\/p>\n
The critics were right to ask these questions, and the Paisley evidence is stronger because they did.<\/p>\n
<\/p>\n
The expanded radiocarbon dating program that characterized the 2012 work was conducted specifically because the original program was insufficient to answer the stratigraphic integrity concerns.<\/p>\n
The fecal lipid biomarker analysis reported in 2020 was developed specifically because the DNA evidence alone was insufficient to answer the coprolite identity concerns.<\/p>\n
The independent blind testing of additional specimens was done specifically because the original analysis needed independent verification.<\/p>\n
Without the criticism, there would have been no incentive to do any of this additional work.<\/p>\n
The 2008 paper, left unchallenged, would have remained a remarkable claim with insufficient supporting evidence.<\/p>\n
The challenge forced the researchers to build the much stronger evidentiary case that now exists.<\/p>\n
<\/p>\n
This is how science is supposed to work.<\/p>\n
An extraordinary claim generates extraordinary scrutiny.<\/p>\n
The scrutiny identifies specific weaknesses in the evidence.<\/p>\n
The researchers respond to those weaknesses by finding new evidence that addresses them through independent methods.<\/p>\n
The result is an evidentiary case that is far more robust than any single piece of evidence could be, precisely because it has been tested from multiple directions and has emerged stronger rather than weaker.<\/p>\n
The Paisley story is a good example of this process at work \u2014 and a reminder that scientific skepticism is not the enemy of discovery.<\/p>\n
<\/p>\n
It is what separates genuine knowledge from wishful thinking.<\/p>\n
The Deeper Uncertainties That Remain<\/p>\n
The Paisley evidence, for all its strength, does not answer every important question about the peopling of the Americas, and any honest account of what the site has contributed must be explicit about what it does not tell us.<\/p>\n
The Paisley evidence does not establish when people first entered the Americas.<\/p>\n
It establishes that people were in Oregon approximately 14,200 to 14,300 years ago.<\/p>\n
This is a local date for a specific geographic location, not a record of the first human entry into the hemisphere.<\/p>\n
<\/p>\n
If people were at Paisley 14,200 years ago, they had already been in the Americas long enough to have moved from the entry point in Beringia to Oregon \u2014 which implies an earlier entry.<\/p>\n
But how much earlier, by which route, and through what specific dispersal pattern are questions that the Paisley evidence does not directly address.<\/p>\n
The Paisley evidence does not establish a specific migration route.<\/p>\n
The people who left the coprolites at Paisley Caves arrived in Oregon somehow, but whether they came by a coastal route, through the ice-free corridor between the Laurentide and Cordilleran ice sheets, or by some other path is not determinable from the Paisley evidence alone.<\/p>\n
The Paisley evidence does not establish the genetic identity of the pre-Clovis people in the complete sense that a whole-genome analysis would provide.<\/p>\n
<\/p>\n
The mitochondrial DNA evidence establishes maternal haplogroups \u2014 one thread in the complex tapestry of ancestry.<\/p>\n
It does not provide paternal lineage, nuclear genome profile, or the kind of comprehensive genetic portrait that would allow detailed comparison with specific modern populations.<\/p>\n
And critically, the Paisley evidence does not establish the cultural identity of the people who occupied the site.<\/p>\n
The archaeological materials \u2014 the coprolites, the Western Stemmed points, the fiber artifacts \u2014 document technological behavior, dietary practice, and the use of space.<\/p>\n
They do not document the language those people spoke, the social organization of their communities, the specific spiritual practices they maintained, or the relationships between their community and other contemporary communities in the region.<\/p>\n
<\/p>\n
The attempt to connect ancient archaeological evidence to specific modern tribal identities is a recurring source of tension in American archaeology, and for good reasons.<\/p>\n
The temporal distance between 14,000-year-old evidence and any modern community is enormous \u2014 enormous enough for populations to move, languages to change, cultural traditions to transform, and biological ancestry to be diluted through admixture with other groups.<\/p>\n
Drawing straight lines from ancient coprolites to modern tribal identities requires much more evidence than the Paisley site alone provides.<\/p>\n
This does not mean that the Paisley evidence is irrelevant to Indigenous peoples and their histories.<\/p>\n
It is deeply relevant.<\/p>\n
<\/p>\n
The evidence demonstrates human presence in the Great Basin region thousands of years before Clovis, establishing the deep antiquity of Indigenous occupation of this part of North America.<\/p>\n
The mitochondrial haplogroups identified are founding lineages of Native American ancestry.<\/p>\n
The archaeological evidence documents specific adaptations to the Great Basin environment that are ancestral, in a broad sense, to the cultural traditions of the Indigenous peoples who have occupied this region through the historical period and the present.<\/p>\n
But the connection is general rather than specific, ancestral rather than genealogically precise, and any attempt to use the Paisley evidence to claim or assign specific tribal identities should be resisted.<\/p>\n
The Indigenous Context of Paisley Caves<\/p>\n
<\/p>\n
The land where the Paisley Caves are located is within the ancestral territory of multiple Indigenous nations of the northern Great Basin, including the Northern Paiute and Klamath peoples.<\/p>\n
These nations have their own oral traditions, their own accounts of their relationships to the land and its history, and their own perspectives on what the archaeological evidence means for their communities.<\/p>\n
The relationship between ancient archaeological evidence and living Indigenous communities is not simply one of passive reception \u2014 of communities waiting to learn from scientists what their own history was.<\/p>\n
Indigenous peoples have maintained continuous relationships with their ancestral landscapes through the generations, and the knowledge embedded in those relationships \u2014 oral traditions, place names, ecological knowledge, ceremonial practices \u2014 represents a different kind of historical record that can complement and enrich the archaeological and genetic evidence.<\/p>\n
<\/p>\n
At the same time, the connection between the specific people who occupied the Paisley Caves 14,000 years ago and any specific modern Indigenous community cannot be established by archaeological evidence alone.<\/p>\n
The scale of demographic change \u2014 the movements of populations, the replacement of some groups by others, the mixing of different populations over thousands of years \u2014 that has occurred since the late Pleistocene means that the genetic and cultural continuity between ancient and modern populations is a complex question that requires its own specific evidence.<\/p>\n
What the Paisley evidence does establish, with considerable strength, is the deep antiquity of human presence in the Great Basin.<\/p>\n
It establishes that people were living in this landscape, exploiting its resources, and using the specific caves that are part of the ancestral land of the Indigenous peoples who have occupied the region through the historical period.<\/p>\n
<\/p>\n
This deep antiquity is consistent with and supports the Indigenous communities’ understanding of their long presence in their homelands.<\/p>\n
The repatriation frameworks established by the Native American Graves Protection and Repatriation Act apply to the Paisley material, and consultation with affiliated tribes has been part of the research process at the site.<\/p>\n
The cultural affiliation of the Paisley remains is a matter that the relevant federal agencies and tribal nations have addressed through the required consultation process.<\/p>\n
The researchers who have worked at Paisley have, in varying degrees, engaged with the Indigenous communities of the region as part of their research activities.<\/p>\n
The University of Oregon Museum of Natural and Cultural History, which has been the primary institutional home for the Paisley research, has responsibilities under NAGPRA and under its own institutional values to engage respectfully with the descendant communities connected to the materials it holds.<\/p>\n
<\/p>\n
What Comes After Clovis and What Paisley Tells Us About It<\/p>\n
The relationship between the Paisley Caves evidence and the post-Clovis archaeological record of the Great Basin and surrounding regions is an important part of the site’s significance, and one that is sometimes underemphasized in accounts focused on the pre-Clovis headline.<\/p>\n
The Western Stemmed point tradition documented at Paisley did not simply appear and disappear.<\/p>\n
It was part of a technological tradition that extended through the early Holocene and that contributed to the development of the diverse archaeological cultures of the western Great Basin in the subsequent millennia.<\/p>\n
Understanding the Paisley evidence requires understanding it not just as a pre-Clovis episode but as the beginning of a long regional occupation history that connects to the archaeological record of the Great Basin through thousands of years of subsequent development.<\/p>\n
<\/p>\n
The early Holocene archaeological record of the Great Basin documents the rapid adaptation of human populations to the changing conditions that followed the end of the last Ice Age.<\/p>\n
As Lake Chewaucan shrank to its modern remnant, as the mammoth steppe gave way to sagebrush and other xeric-adapted communities, as the large game animals of the Pleistocene disappeared from the region, the people of the Great Basin adapted.<\/p>\n
They developed increasingly sophisticated strategies for exploiting the plant resources of the arid basin, for managing the episodic availability of water in a landscape where water sources could be separated by many miles, and for maintaining viable populations through periods of environmental stress that would have been challenging even for well-adapted communities.<\/p>\n
This adaptive capacity \u2014 the ability to respond to major environmental change by modifying subsistence strategies, technological systems, and potentially settlement patterns \u2014 is one of the most impressive aspects of the archaeological record of the Great Basin.<\/p>\n
<\/p>\n
The people who were at Paisley Caves 14,000 years ago were the ancestors, in a biological and cultural sense, of the people who would navigate the profound environmental changes of the early Holocene and establish the long-term patterns of Great Basin occupation that continue in modified form to the present.<\/p>\n
The Cave as Document<\/p>\n
One of the ways to appreciate what Paisley Caves has contributed is to think about what kind of document a cave is \u2014 what it records, how it records it, and what can be read from the record it creates.<\/p>\n
A cave is, in one sense, a passive collector.<\/p>\n
It receives what falls into it, blows into it, is carried into it by animals, or is deliberately deposited in it by human visitors.<\/p>\n
Over thousands of years, this accumulation creates a sediment archive that preserves materials from many different time periods in a roughly chronological sequence.<\/p>\n
<\/p>\n
The older materials are generally deeper, the newer materials are generally closer to the surface, and the vertical position of materials within the sequence provides a relative chronology that can be converted to an absolute chronology through radiocarbon dating.<\/p>\n
But a cave is also an active environment.<\/p>\n
The same wind that blows sediment into a cave can also rearrange what is already there.<\/p>\n
The animals that use the cave \u2014 including the humans who visit it \u2014 can disturb the accumulated sediment.<\/p>\n
Water infiltrating through the cave ceiling or floor can transport materials horizontally and vertically.<\/p>\n
The very processes that make caves good preservation sites also introduce complexity into the stratigraphic record that must be carefully documented and understood.<\/p>\n
The Paisley Caves record, read carefully and with appropriate attention to its complexities, preserves a detailed archive of environmental and human history in the northern Great Basin spanning more than 14,000 years.<\/p>\n
<\/p>\n
That archive includes direct evidence of human presence \u2014 the coprolites, the artifacts, the organic materials \u2014 but it also includes environmental information: pollen from plants growing in and around the cave, the bones of animals that were killed or consumed nearby, and chemical records of changing conditions preserved in the sediment itself.<\/p>\n
Reading this archive requires the full range of methodological tools available to modern archaeology and natural science \u2014 radiocarbon dating, ancient DNA analysis, fecal lipid biomarker chemistry, micromorphology, isotopic analysis, palynology, and archaeological artifact analysis.<\/p>\n
No single method is sufficient.<\/p>\n
The power of the Paisley evidence comes from the convergence of multiple independent methods, each with its own limitations and its own strengths, pointing to the same general conclusion through different routes.<\/p>\n
The Scale of the Question the Caves Could Not Have Known They Were Answering<\/p>\n
<\/p>\n
When the people who left the coprolites at Paisley Caves 14,200 years ago made their camp above Lake Chewaucan, they were not thinking about the peopling of the Americas.<\/p>\n
They were not trying to answer a question that had not yet been asked in any form they would have recognized.<\/p>\n
They were doing what people do: finding shelter, processing food, managing their biological needs, and living the specific daily life of their specific time and place.<\/p>\n
The coprolites they left behind were not intended as a message to the future.<\/p>\n
They were a biological trace of ordinary life, no more remarkable to the people who produced them than the waste of any other day’s existence.<\/p>\n
<\/p>\n
They happened to desiccate rapidly, to be buried in sediment that preserved their organic chemistry, to be located in a cave that maintained the right conditions for preservation across 14,000 years, and to survive the accidental disturbances \u2014 animal activity, occasional water movement, the inevitable geological processes of a dynamic landscape \u2014 that might have destroyed them at any point.<\/p>\n
That they survived, and that the chemistry of their organic content turned out to carry the specific information needed to place their producers within the founding lineages of the Indigenous peoples of the Americas, is the kind of improbable gift that archaeological science occasionally receives from the past.<\/p>\n
The people at Paisley 14,000 years ago were, by every available measure, full human beings.<\/p>\n
They had a material culture sophisticated enough to produce the Western Stemmed points found in the caves.<\/p>\n
<\/p>\n
They had a dietary knowledge comprehensive enough to process the plant foods identified in the coprolites.<\/p>\n
They had the organizational capacity to maintain themselves in a challenging landscape.<\/p>\n
They had relationships with each other, knowledge of the landscape they inhabited, and \u2014 almost certainly \u2014 the full range of social, spiritual, and cultural life that we associate with human communities everywhere.<\/p>\n
The specific content of that cultural life \u2014 the languages they spoke, the stories they told, the ceremonies they conducted, the relationships that structured their communities \u2014 is not preserved in the Paisley Caves archive.<\/p>\n
The sediment is not a complete record.<\/p>\n
<\/p>\n
It is a partial record, preserving the hardest and most chemically stable aspects of daily life while the softer, more ephemeral aspects of culture dissolve with time.<\/p>\n
What survives is enough to establish their presence, to situate them within the biological lineage of the founding populations of the Americas, and to document some of the specific ways in which they were exploiting the resources of the Great Basin landscape 14,000 years ago.<\/p>\n
It is not enough to give them names, to reconstruct their social world in detail, or to determine the precise mechanisms by which their descendants came to occupy the full range of Great Basin environments in the subsequent millennia.<\/p>\n
Those questions remain open, as they should \u2014 not as failures of research, but as honest characterizations of the limits of what the preserved record can tell us.<\/p>\n
<\/p>\n
The Evidence That Survived by Surviving Challenge<\/p>\n
The Paisley Caves story is ultimately a story about what happens when a remarkable claim is subjected to the kind of rigorous, sustained scientific challenge that distinguishes genuine knowledge from unsubstantiated assertion.<\/p>\n
The original 2008 claim was remarkable: human mitochondrial DNA, directly dated to before Clovis, from preserved feces in an Oregon cave.<\/p>\n
It was the kind of result that could have been dismissed \u2014 and nearly was, by critics who raised legitimate concerns about every specific element of the evidentiary chain.<\/p>\n
But the researchers who made the original claim did not simply reassert that they were right.<\/p>\n
<\/p>\n
They went back to the caves with more tools, more methods, more questions, and more rigorous documentation.<\/p>\n
They collected hundreds of radiocarbon dates instead of a handful.<\/p>\n
They subjected additional coprolites to independent blind testing at different laboratories.<\/p>\n
They engaged the specific objections about stratigraphic integrity with detailed micromorphological analysis.<\/p>\n
And eventually, years after the original publication, their colleagues applied fecal lipid biomarker chemistry to provide the independent confirmation of coprolite identity that DNA analysis alone could not supply.<\/p>\n
The result is an evidentiary case that is far stronger than the 2008 paper alone.<\/p>\n
<\/p>\n
It is not perfect \u2014 no archaeological evidence of this kind ever is, and honest researchers acknowledge the specific remaining uncertainties.<\/p>\n
But it is the kind of evidence that comes from a claim that has been tested from multiple directions and has emerged from each test with its core interpretation intact and supported.<\/p>\n
The central finding \u2014 that people were in the Oregon Great Basin before the conventional Clovis horizon, approximately 14,200 years ago, carrying the founding maternal lineages of Native American ancestry \u2014 is supported by directly dated biological specimens, confirmed by independent DNA analysis, corroborated by fecal lipid biomarker chemistry, consistent with a dense network of associated radiocarbon dates, and accompanied by a contemporaneous lithic technology distinct from Clovis.<\/p>\n
This is strong evidence.<\/p>\n
<\/p>\n
It is not proof of everything that the most enthusiastic early accounts claimed, and it should not be presented that way.<\/p>\n
It does not tell us exactly when the first Americans entered the hemisphere.<\/p>\n
It does not tell us how many founding populations there were or exactly what routes they used.<\/p>\n
It does not tell us the specific cultural or social identities of the pre-Clovis people whose traces are preserved in the cave sediment.<\/p>\n
What it does, firmly and with considerable supporting detail, is place people in the Far West of North America before the Clovis horizon.<\/p>\n
It contributes, alongside the evidence from Monte Verde, Cooper’s Ferry, White Sands, Bluefish Caves, and a growing list of other sites, to a picture of the Americas as a hemisphere that was inhabited before Clovis \u2014 by people who were the founders of the same maternal lineages carried by Native American peoples today.<\/p>\n
<\/p>\n
The dried biological trace that could have been ignored \u2014 one small dark mass in the sediment of an Oregon cave \u2014 became evidence in one of the most important debates in the history of American archaeology.<\/p>\n
Its power lay not in what it initially claimed, but in what it demonstrated when it was challenged: that the presence of people in Oregon before Clovis was not a spectacular artifact of methodological error, but a genuine historical fact that new methods and new scrutiny only confirmed more firmly.<\/p>\n
The question the coprolite answered was smaller than the question it opened.<\/p>\n
That is often how science works.<\/p>\n
<\/p>\n
And the question it opened \u2014 about who the first Americans were, how they arrived, by what routes and in what numbers, and how the diverse peoples of the Americas descended from that founding event \u2014 remains one of the most fascinating unresolved questions in the study of human prehistory.<\/p>\n
The caves at the edge of Lake Chewaucan are still there, in south-central Oregon, above the dry basin where a great lake used to be.<\/p>\n
They have not finished yielding their evidence.<\/p>\n
The science has not finished asking its questions.<\/p>\n
The people who left those traces 14,000 years ago could not have imagined that their biological waste would one day become evidence in a scientific controversy debated in peer-reviewed journals across the world.<\/p>\n
They could not have imagined the laboratories, the radiocarbon accelerators, the genetic sequencers, or the mass spectrometers that would eventually be brought to bear on what they left behind.<\/p>\n
<\/p>\n
What they could not have imagined, we can now begin to understand.<\/p>\n
And what we now understand points, through all the complexity and all the remaining uncertainty, to one durable fact: people were here, in this landscape, before Clovis \u2014 and the evidence they left behind, humble as it was, survived 14,000 years and a century of scientific argument to say so.<\/p>\n
\u2014 END \u2014<\/p>\n
\u2014 EXTENDED SECTIONS \u2014<\/p>\n
The Chemistry of Preservation: Why Great Basin Caves Work<\/p>\n
The specific preservation conditions that made the Paisley coprolites informative need to be understood in some detail, because the preservation is not accidental \u2014 it reflects specific chemical and physical characteristics of the cave environment that archaeologists have learned to recognize as predictors of organic material survival.<\/p>\n
<\/p>\n
The northern Great Basin environment during the late Pleistocene was significantly more humid than today \u2014 the presence of Lake Chewaucan demonstrates this plainly \u2014 but it was not as persistently wet as the environments of many other regions where organic preservation is poor.<\/p>\n
The caves above the lake shoreline experienced seasonal variation in humidity, but the consistent temperatures and the protection from direct precipitation provided by the overhanging rock created microenvironments that were, in the relevant periods, substantially drier than the surrounding landscape.<\/p>\n
Desiccation is the most important single factor in the preservation of biological material like feces.<\/p>\n
When biological tissue desiccates rapidly \u2014 when the water content drops below the threshold needed for microbial activity \u2014 the decomposition process is essentially suspended.<\/p>\n
The organic molecules that would otherwise be metabolized by bacteria, fungi, and other decomposers remain intact in the desiccated structure, including both the physical components of the feces (plant fiber, bone fragments, seed coats) and the molecular components (DNA, lipids, proteins).<\/p>\n
<\/p>\n
In the Paisley Caves, the combination of south-facing orientation (maximizing solar warming and evaporation during the summer season), the protection from rain, and the alkaline chemistry of the sediment created conditions where desiccation of deposited biological material could occur relatively quickly and where the desiccated material could remain in a stable state for extended periods.<\/p>\n
The alkaline chemistry of the cave sediment is particularly important for DNA preservation.<\/p>\n
DNA degrades through several mechanisms, and one of the most important is acid hydrolysis \u2014 the chemical breakdown of the DNA backbone by acidic conditions.<\/p>\n
In alkaline sediments, this mechanism is suppressed, allowing DNA to survive longer than it would in the acidic conditions of many forest soils or humid sediment environments.<\/p>\n
The Great Basin’s carbonate-rich sediments are naturally alkaline, contributing to the preservation of both the DNA and the lipid molecules that the 2020 study analyzed.<\/p>\n
<\/p>\n
The cooling of the cave environment at night and in winter also contributes to preservation by reducing the rate of chemical reactions that degrade organic molecules.<\/p>\n
Temperature is a critical determinant of the rate of chemical processes, including both the biological degradation of DNA and proteins and the non-biological chemical reactions that can alter organic molecules over time.<\/p>\n
Lower average temperatures slow all of these processes, extending the window of time during which ancient molecules remain intact and informative.<\/p>\n
Understanding these preservation conditions has practical implications for how archaeologists approach sites in arid cave environments.<\/p>\n
The same conditions that preserved the Paisley coprolites may preserve similar materials at other sites across the Great Basin and surrounding regions \u2014 sites that have not yet been systematically examined for coprolite content or that have not had their coprolite assemblages subjected to ancient DNA or lipid biomarker analysis.<\/p>\n
<\/p>\n
The Paisley work has opened a methodological window that is potentially applicable to a wide range of arid cave and rock shelter sites across the western United States.<\/p>\n
Dennis Jenkins and the Research Program<\/p>\n
The Paisley Caves research represents a sustained, multi-decade research program, not a single excavation season or a single paper.<\/p>\n
Understanding the scope and continuity of the research program helps explain why the evidentiary case for the site is as robust as it is.<\/p>\n
Dennis Jenkins of the University of Oregon Museum of Natural and Cultural History has been the lead archaeologist at the site across the period of the research that produced the coprolite evidence.<\/p>\n
Jenkins’s approach to the site has been characterized by systematic, careful excavation, detailed documentation, and a commitment to building a comprehensive understanding of the site’s history rather than simply extracting the most dramatic evidence.<\/p>\n
<\/p>\n
The multi-season nature of the research has allowed the team to expand the area of excavation incrementally, to apply new analytical methods as they became available, and to return to specific areas of the site with additional questions as the initial results generated those questions.<\/p>\n
This is the normal rhythm of productive archaeological research at complex sites, but it requires sustained institutional support and a long-term commitment from the researchers and their institutions that not all archaeological projects receive.<\/p>\n
The collaboration between Jenkins’s field program and the laboratory scientists who conducted the ancient DNA analysis and the fecal lipid biomarker work reflects another important aspect of modern archaeological research: the integration of specialist expertise across multiple disciplines.<\/p>\n
No single researcher or research group has the full range of expertise needed to carry out all aspects of the Paisley research program.<\/p>\n
<\/p>\n
The combination of field archaeology, radiocarbon dating expertise, ancient DNA analysis, and organic chemistry requires collaboration across disciplinary boundaries and across institutional affiliations.<\/p>\n
This kind of interdisciplinary collaboration is increasingly characteristic of cutting-edge archaeological research, and it is one of the factors that distinguishes the Paisley research from earlier work at the site.<\/p>\n
The methodological tools available to Cressman in the 1930s, or even to the researchers who worked at the site in the following decades, were fundamentally different from what Jenkins and his collaborators have been able to bring to bear.<\/p>\n
The availability of AMS radiocarbon dating, ancient DNA analysis, and mass spectrometry for lipid biomarker identification has transformed what can be learned from materials like the Paisley coprolites.<\/p>\n
<\/p>\n
The Radiocarbon Number Behind the Headlines<\/p>\n
The specific dates reported in the Paisley research deserve careful attention, because the way those dates are expressed in scientific publications differs from how they are typically reported in popular accounts, and the difference matters for accuracy.<\/p>\n
Radiocarbon dating produces dates expressed in radiocarbon years before present, where “before present” is standardly defined as before 1950 CE.<\/p>\n
The conversion from radiocarbon years to calibrated calendar years \u2014 the conversion required to express the age of a specimen in terms of actual elapsed calendar time \u2014 is not a simple linear conversion.<\/p>\n
The amount of radiocarbon-14 in the atmosphere has varied over time, and the calibration curve that converts radiocarbon years to calendar years reflects these variations.<\/p>\n
<\/p>\n
For the period around 14,000 to 14,500 years ago, the calibration curve has a specific shape that means that radiocarbon ages in a specific range map to a somewhat wider range of calibrated calendar ages.<\/p>\n
The specific calibrated ages reported for the Paisley coprolites in the original 2008 paper, and the refined dates from the expanded radiocarbon program of the 2012 paper, reflect this calibration.<\/p>\n
Popular summaries of the Paisley evidence frequently cite a round number \u2014 “14,300 years old” or “14,200 years old” \u2014 as the age of the oldest coprolites.<\/p>\n
These figures are reasonable approximations of the calibrated calendar age range reported in the primary literature, but they should be understood as approximations rather than precise measurements.<\/p>\n
The actual calibrated age distribution for the oldest specimens spans a range of years rather than a single point, and the central value of that range is what popular accounts typically report.<\/p>\n
<\/p>\n
The distinction between radiocarbon years and calibrated calendar years is particularly important when comparing the Paisley dates to the conventional Clovis horizon, which is also expressed in calibrated calendar years.<\/p>\n
The approximately 1,000-year difference between the oldest Paisley dates and the conventional Clovis horizon is expressed in calibrated calendar years, not radiocarbon years.<\/p>\n
Making this comparison correctly requires converting all dates to the same temporal framework \u2014 calibrated calendar years before present \u2014 before drawing conclusions about their relative positions in time.<\/p>\n
The 2012 Jenkins paper used a dense program of radiocarbon dates to build what is effectively a Bayesian chronological model of the site’s occupation sequence \u2014 a model that uses the stratigraphic order of the samples (older samples should be below younger samples in an undisturbed sequence) and the radiocarbon dates to produce refined probability distributions for the age of each phase of occupation.<\/p>\n
This approach produces more precise and more reliable age estimates than simple one-date-at-a-time comparisons, and it allows researchers to assess the consistency of the dates with the stratigraphic sequence \u2014 identifying any anomalies that might indicate disturbance.<\/p>\n
<\/p>\n
The result of the Bayesian chronological modeling was a well-supported age estimate for the pre-Clovis layers at Paisley that is consistent with, and substantially more precisely characterized than, the original estimates from the 2008 paper.<\/p>\n
The Parallel Technology Argument<\/p>\n
The argument made in the 2012 Jenkins paper that Western Stemmed technology was parallel to Clovis rather than derived from it deserves careful examination, because it touches on one of the most fundamental questions in the study of early Americans: how many founding dispersals were there, and what was the relationship between them?<\/p>\n
The Clovis-first model, in its strongest form, proposed a single founding dispersal into the Americas \u2014 a population that crossed from Beringia into North America and rapidly spread across both continents, bringing with it the Clovis technological tradition.<\/p>\n
Under this model, all subsequent technologies, including Western Stemmed technology, would be derived from Clovis \u2014 modifications and adaptations of the Clovis toolkit to different environments and different prey animals.<\/p>\n
<\/p>\n
The parallel technology argument challenges this model.<\/p>\n
If Western Stemmed technology appears in the archaeological record contemporaneously with Clovis technology, and if the two traditions show sufficient technical and morphological differences to suggest independent development rather than one being derived from the other, then the Clovis-first model in its strongest form cannot be correct.<\/p>\n
Either there were multiple founding dispersals \u2014 with different groups bringing different technological traditions \u2014 or the founding population was already technologically diverse before the dispersal into the Americas.<\/p>\n
The evidence for parallel development is not confined to Paisley.<\/p>\n
<\/p>\n
Multiple sites in the western United States have produced Western Stemmed points in contexts that appear to be contemporaneous with or older than the Clovis horizon, and the geographic distribution of Western Stemmed technology in the western Great Basin, the Columbia Plateau, and surrounding regions does not show the pattern of derivation from a Clovis founding that the Clovis-first model would predict.<\/p>\n
The most cautious interpretation of this evidence is that it complicates the Clovis-first model without definitively replacing it with an alternative.<\/p>\n
The archaeological evidence is consistent with multiple possible scenarios: a single founding dispersal that rapidly differentiated technologically as different groups adapted to different environments; a founding dispersal that was already diverse and that distributed different technological starting points to different geographic regions; or multiple independent founding dispersals that brought different technologies from different northeastern Asian source populations.<\/p>\n
Distinguishing among these possibilities requires evidence that goes beyond the archaeological record alone \u2014 specifically, the ancient DNA evidence that can characterize the genetic relationships among the earliest Americans and their northeastern Asian ancestors.<\/p>\n
<\/p>\n
The integration of archaeological and genetic evidence is one of the most productive research directions in the field, and the Paisley evidence has contributed to both sides of this integration.<\/p>\n
The Bone Tool and Fiber Evidence in Context<\/p>\n
The fiber and basketry evidence from Paisley Caves \u2014 twisted fiber materials that appear in contexts consistent with pre-Clovis or Clovis-contemporaneous occupation \u2014 connects the site to a broader archaeological record of early fiber technology in the western United States that has not received as much public attention as the lithic technology evidence.<\/p>\n
Fiber technologies \u2014 the production of cordage, basketry, netting, and textile materials from plant and animal fibers \u2014 are among the most important categories of human technological achievement, enabling a wide range of applications from carrying equipment to constructing shelter to capturing fish and small game.<\/p>\n
But fiber technologies leave an archaeological record that is far more fragile and far less well-preserved than stone tool technologies, because organic fiber degrades rapidly in most archaeological contexts.<\/p>\n
<\/p>\n
The preservation of fiber artifacts at Paisley Caves is exceptional precisely because of the same conditions that preserved the coprolites.<\/p>\n
Dry alkaline caves in arid environments are among the most favorable contexts for the preservation of organic materials, and the archaeological record of the Great Basin and surrounding regions has produced some of the best-preserved examples of early fiber technology anywhere in the Western Hemisphere.<\/p>\n
The age of the Paisley fiber evidence \u2014 whether it clearly predates Clovis or falls within the Clovis age range \u2014 is a question that requires careful stratigraphic attribution and dating.<\/p>\n
The materials reported in the Jenkins research program have been dated as part of the broader radiocarbon chronological framework for the site, and their relationship to the pre-Clovis layers has been part of the overall argument for early occupation.<\/p>\n
<\/p>\n
The significance of fiber technology in the Paisley context extends beyond the specific dates.<\/p>\n
The ability to produce twisted fiber cordage requires knowledge of appropriate plant sources, understanding of fiber preparation techniques (stripping, drying, or retting plant material to produce workable fiber), and the physical skill to twist fibers under consistent tension to produce strong, regular cordage.<\/p>\n
This is not a simple or rudimentary craft \u2014 it is a sophisticated and technically demanding technology that takes considerable practice and learning to master.<\/p>\n
Cordage enables other technologies: the hafting of stone tools to wooden or bone shafts requires binding material that holds reliably under the stress of use.<\/p>\n
<\/p>\n
Nets and snares for capturing small game require specific types of cordage and specific knotting techniques.<\/p>\n
Carrying devices \u2014 bags, baskets, nets \u2014 that extend the ability of people to transport food, water, and equipment are all fiber-dependent technologies.<\/p>\n
The presence of fiber production at Paisley, even in fragmentary evidence, documents a material culture that was substantially more comprehensive than the stone tool evidence alone would suggest.<\/p>\n
The Seasonal Dimension of Cave Occupation<\/p>\n
The Paisley Caves were not necessarily occupied year-round.<\/p>\n
The evidence from the coprolites and associated materials suggests that the site may have been a seasonal destination \u2014 one location in a broader pattern of movement through the Great Basin landscape that took people to different resources at different times of year.<\/p>\n
<\/p>\n
Understanding early hunter-gatherer occupation in terms of seasonal mobility patterns, rather than as simple year-round habitation of fixed sites, is one of the important insights that has developed in the archaeological study of the Great Basin and surrounding regions.<\/p>\n
The Great Basin environment is highly seasonal, with different resources available in different locations at different times of year.<\/p>\n
Effective exploitation of this environment requires knowledge of which resources are available where and when, and the ability to move through the landscape to be in the right place at the right time.<\/p>\n
The south-facing location of the Paisley Caves \u2014 which maximizes solar warming in winter \u2014 suggests that the caves may have been particularly attractive in the colder months of the year, when their thermal advantage would have been most significant.<\/p>\n
The caves’ position above the lake would have given occupants access to aquatic resources \u2014 waterfowl, fish \u2014 that would have been available in winter and early spring.<\/p>\n
<\/p>\n
The shelter from wind and cold that the cave architecture provided would have been particularly valuable in the coldest months.<\/p>\n
But the caves were not necessarily used exclusively in winter.<\/p>\n
The plant food evidence from the coprolites includes materials that would have been available in summer and fall \u2014 seed crops that ripen in late summer, for example, or plant parts that are harvested in the fall before frost destroys them.<\/p>\n
The temporal span of occupation at the site, documented across many coprolites from multiple periods, likely reflects multiple seasons and multiple years of use rather than a single extended occupation.<\/p>\n
The pattern of seasonal mobility associated with the Paisley site would have connected it to a network of other sites across the northern Great Basin \u2014 other caves, other rock shelters, other open-air camps \u2014 that formed a seasonal circuit through which a community moved over the course of a year.<\/p>\n
<\/p>\n
Understanding Paisley Caves fully requires understanding its place in this broader landscape of habitation, which remains only partially understood.<\/p>\n
The Macrobotanical Evidence and What People Were Eating<\/p>\n
The plant remains identified within the Paisley coprolites provide direct evidence of what the cave’s human occupants were eating \u2014 evidence that is not mediated by the preservation biases that affect botanical remains in open-air contexts, because the coprolites preserved plant materials that would have decayed rapidly if deposited in the sediment alone.<\/p>\n
The specific plant taxa identifiable from coprolite contents reflect the flora of the late Pleistocene Great Basin \u2014 a flora that included many of the same genera as the modern Great Basin, but with different proportional representations of species reflecting the cooler, somewhat wetter conditions of the late Pleistocene.<\/p>\n
<\/p>\n
Seed-bearing plants are among the most commonly identified items in Great Basin coprolites from all time periods, reflecting the importance of small seeds as a dietary staple in an environment where large-seeded cereal crops are not native.<\/p>\n
The processing of small seeds \u2014 grinding them with stone tools to produce a paste or flour, or cooking them in liquid to make a porridge or gruel \u2014 is documented both in the macrobotanical remains of the coprolites and in the ground stone tools (manos and metates) that appear in Great Basin archaeological sites from early periods.<\/p>\n
The presence of specific types of bulrush and other aquatic and riparian plant materials in some coprolites is consistent with the exploitation of the lake-edge environment \u2014 harvesting the starchy roots, seeds, and pollen of plants that grew in or near Lake Chewaucan.<\/p>\n
Bulrush and related plants are nutritionally dense and productive, and their exploitation would have been a logical component of the subsistence strategy of people living near a pluvial lake.<\/p>\n
<\/p>\n
Animal food evidence in the coprolites includes small rodent bones, fish scales and bones, and the occasional larger mammal hair or bone fragment.<\/p>\n
This evidence is consistent with a broad-spectrum diet \u2014 the exploitation of a wide range of animal food sources rather than specialization in a single prey type \u2014 that is characteristic of effective hunter-gatherer subsistence in environments where any single prey type can be unreliable.<\/p>\n
The combination of plant and animal evidence in the Paisley coprolites documents a human population that was not dependent on megafauna hunting alone.<\/p>\n
The Pleistocene megafauna \u2014 mammoths, horses, and the other large animals of the late Pleistocene \u2014 appear to have been part of the subsistence landscape of the earliest Americans, and some early sites document unambiguous evidence of megafauna hunting or processing.<\/p>\n
<\/p>\n
But the Paisley evidence suggests that the people who occupied these Oregon caves were exploiting a diverse array of resources \u2014 the plants of the lake margin, the fish of the lake, the small mammals of the surrounding shrublands, and potentially the larger animals of the region \u2014 in a pattern that is fundamentally opportunistic and ecologically sophisticated.<\/p>\n
This broad-spectrum dietary approach is consistent with what ecologists would predict for optimal foraging in the Great Basin environment: in a landscape where any single resource is spatially and temporally variable, diversifying across multiple resource types reduces the risk of starvation and maximizes the overall caloric efficiency of the food-getting strategy.<\/p>\n
The Contribution of Micromorphology<\/p>\n
The micromorphological analysis of the Paisley Cave sediments \u2014 the examination of thin sections of undisturbed sediment under a microscope \u2014 contributed to the evaluation of the stratigraphic integrity concerns in ways that deserve specific attention.<\/p>\n
Micromorphology is a specialized subfield that bridges geology, soil science, and archaeology.<\/p>\n
<\/p>\n
Micromorphologists take small blocks of sediment intact from an archaeological site, impregnate them with resin to hold their structure in place, slice them into thin sections approximately 30 micrometers thick, and examine those sections under transmitted light and polarized light microscopes.<\/p>\n
At this scale of observation, features that are invisible to the naked eye become apparent: the arrangement of sediment particles, the presence of biological remains (plant cells, fungal spores, bone fragments, charcoal), the chemical stains left by organic compounds, and the traces of biological activity (root channels, burrows, earthworm pedoturbation) that indicate post-depositional disturbance.<\/p>\n
The micromorphological analysis of the Paisley Caves sediment was conducted specifically to address the stratigraphic integrity concerns raised by the critics of the 2008 paper.<\/p>\n
The questions being asked were: do the deepest layers at the site show evidence of significant disturbance that would mix materials from different time periods?<\/p>\n
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Are there features in the sediment that would indicate vertical movement of materials from upper layers into lower ones?<\/p>\n
Are the coprolites in primary depositional context \u2014 lying where they were originally deposited \u2014 or have they been moved by post-depositional processes?<\/p>\n
The micromorphological results were generally supportive of stratigraphic integrity in the pre-Clovis layers, though they also documented the complexity of cave sediment processes in ways that required nuanced interpretation.<\/p>\n
The analysis identified the types of sediment that dominated different layers, documented the transitions between layers, and characterized the degree of biological and physical disturbance in each.<\/p>\n
The overall conclusion was that the pre-Clovis layers were sufficiently intact to support the interpretation that the materials recovered from them were in primary or near-primary depositional context.<\/p>\n
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This does not mean that the pre-Clovis layers were perfectly undisturbed \u2014 no cave sediment is.<\/p>\n
It means that the level of disturbance was insufficient to undermine the basic stratigraphic interpretation that the deepest layers contained material that was deposited before the Clovis horizon.<\/p>\n
The Interaction Between Evidence Types<\/p>\n
One of the most intellectually satisfying aspects of the Paisley Caves research program is the way in which different types of evidence have been brought into dialogue with each other, each addressing questions that other types of evidence cannot answer alone.<\/p>\n
The radiocarbon dates establish when things happened \u2014 or, more precisely, they establish the probability distribution of when specific organic materials were alive.<\/p>\n
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When radiocarbon dates from multiple different types of material in the same stratigraphic layer are consistent with each other, they provide strong evidence that those materials were deposited at approximately the same time.<\/p>\n
The ancient DNA provides information about who was present \u2014 specifically, about the maternal lineage of the people whose biological material is preserved in the coprolites.<\/p>\n
This information is powerful but limited: it establishes a biological connection to Native American founding populations without establishing specific cultural or tribal identity, and it is subject to the contamination and DNA movement concerns that the critics correctly identified.<\/p>\n
The fecal lipid biomarkers address the identity of the coprolite producer through an entirely different biochemical pathway.<\/p>\n
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They answer the question “did a human produce this specific specimen?” in a way that is independent of the DNA evidence, using chemical compounds that are produced by a fundamentally different biological process.<\/p>\n
The lithic artifacts document the presence of technological behavior \u2014 the production and use of stone tools \u2014 and the specific technology used (Western Stemmed rather than Clovis) addresses the broader question of the technological relationships among early American populations.<\/p>\n
The macrobotanical and faunal remains document the specific resources being exploited and the processing behaviors applied to those resources \u2014 information that is not available from the lithic or DNA evidence.<\/p>\n
And the micromorphological and stratigraphic analysis provides the spatial and temporal framework within which all the other evidence must be interpreted \u2014 establishing that the different categories of evidence were deposited at the same time, in the same place, and can be read as parts of a single coherent record of human occupation.<\/p>\n
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No single one of these evidence types is sufficient to establish the Paisley claim on its own.<\/p>\n
Together, converging from different analytical directions toward the same general conclusion, they constitute one of the most robust pre-Clovis evidentiary cases in North American archaeology.<\/p>\n
The Significance for Indigenous History<\/p>\n
The Paisley evidence and the broader debate about pre-Clovis human presence in the Americas are relevant to Indigenous peoples and their histories in ways that go beyond the academic question of when people first arrived in the hemisphere.<\/p>\n
The question of the antiquity of Indigenous occupation of North America has direct implications for how the relationship between Native peoples and their ancestral lands is understood \u2014 legally, politically, and culturally.<\/p>\n
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Indigenous peoples’ connections to their homelands are not simply matters of historical preference or cultural attachment; they are also the basis for legal rights, treaty obligations, and the recognition of sovereignty that has been the subject of centuries of political struggle.<\/p>\n
The recognition that Indigenous peoples have occupied North America for at least 14,000 years \u2014 and probably significantly longer, given the evidence from Bluefish Caves and other sites \u2014 establishes the deep antiquity of that occupation in a way that scientific evidence can support.<\/p>\n
This does not mean that archaeological science is the arbiter of Indigenous rights or identity; Indigenous communities’ relationships to their homelands do not depend on scientific validation.<\/p>\n
But the scientific record of deep Indigenous antiquity can be an important element in broader arguments about the legitimate place of Indigenous peoples in their ancestral territories.<\/p>\n
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The Paisley evidence specifically contributes to this record by documenting human presence in the northern Great Basin at approximately 14,200 years ago \u2014 a date that places people in the specific geographic region of the Great Basin well before any European could have argued that the land was unoccupied or belonged to no one.<\/p>\n
The specificity of the Paisley evidence \u2014 a specific cave, specific organic materials, specific dates \u2014 gives it a concreteness that general arguments about Indigenous antiquity sometimes lack.<\/p>\n
At the same time, the Paisley evidence should not be used to claim specific cultural or tribal identities for the people documented at the site.<\/p>\n
The distance of 14,000 years, and the complexity of the demographic and cultural changes that have occurred in the Great Basin since then, means that connecting the specific Paisley people to specific modern communities requires evidence beyond what the Paisley record alone provides.<\/p>\n
What the Paisley evidence does establish is the general fact of deep Indigenous presence in the northern Great Basin \u2014 a presence that predates Clovis and that is connected, through the founding maternal haplogroups identified in the coprolite DNA, to the lineages that gave rise to Native American peoples broadly.<\/p>\n
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This general fact is significant and worth establishing clearly, while the more specific questions of tribal affiliation and cultural identity are treated with the caution they require.<\/p>\n
The Great Basin in the Centuries After Paisley<\/p>\n
The Paisley evidence documents a moment \u2014 or rather a series of moments, spanning the period of pre-Clovis and Clovis-contemporaneous occupation \u2014 in the long human history of the northern Great Basin.<\/p>\n
Understanding what came after the Paisley period adds context to the site’s significance.<\/p>\n
In the centuries and millennia following the period documented by the Paisley coprolites, the northern Great Basin experienced significant environmental change.<\/p>\n
Lake Chewaucan, which had been a prominent feature of the landscape during the late Pleistocene, began to shrink as the climate warmed and the glacial melt that had fed it diminished.<\/p>\n
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By the middle Holocene \u2014 roughly 4,000 to 8,000 years ago \u2014 the lake had declined dramatically from its Pleistocene extent, and the Great Basin as a whole experienced a period of increased aridity.<\/p>\n
These environmental changes required significant adaptive responses from the human populations of the region.<\/p>\n
The aquatic resources that the lake had provided \u2014 fish, waterfowl, aquatic plants \u2014 became less abundant as the lake shrank.<\/p>\n
The plant community of the basin changed as species composition shifted in response to the warmer, drier conditions.<\/p>\n
The large game animals of the late Pleistocene \u2014 mammoths and horses \u2014 had gone extinct by the early Holocene, removing some of the largest food sources from the landscape.<\/p>\n
The archaeological record of the Great Basin through the Holocene documents the successive adaptations of human populations to these changing conditions.<\/p>\n
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The development of increasingly sophisticated plant food processing technology \u2014 ground stone tools, food storage technology, knowledge of plant toxins and how to neutralize them \u2014 reflects the growing importance of plant foods in a landscape where large game was less abundant than in the Pleistocene.<\/p>\n