The Genome That Didn’t Fit<\/p>\n
The genome was real.<\/p>\n
The dates were real.<\/p>\n
The burial context was real and carefully documented.<\/p>\n
And yet when the scientists finished their analysis and looked at where the ancient Alaskan infant fit in the growing family tree of ancient American populations, the result did not match what they had expected.<\/p>\n
The child \u2014 a female infant who had been buried approximately 11,500 years ago in a hearth feature at a site in interior Alaska \u2014 was not closely related to any of the Native American populations that geneticists had previously sequenced.<\/p>\n
She was not most similar to the people who had been analyzed from the Great Plains, the Pacific Coast, the Amazon, or any of the other regions where ancient or modern Indigenous American genomes had been studied.<\/p>\n
She was something different.<\/p>\n
Something older-looking, in the specific statistical sense that geneticists use when they describe one lineage as more basal than another.<\/p>\n
She belonged to a previously unidentified branch of the first Americans \u2014 a branch that scientists would call the Ancient Beringians.<\/p>\n
And finding her in Alaska, at a date that placed her among the earliest well-preserved ancient genomes from North America, immediately raised questions that researchers have been working to answer ever since.<\/p>\n
Not questions about whether she was Native American.<\/p>\n
She was \u2014 unambiguously, in every relevant genetic sense.<\/p>\n
The questions were more specific and more interesting than that.<\/p>\n
They were questions about the founding of the Americas itself: about whether the first people to populate the Western Hemisphere came in one founding event or several, about whether Beringia \u2014 the broad land connection between Asia and North America during the Ice Age \u2014 was a thoroughfare or a homeland, and about what happened to the lineage she represented in the thousands of years that followed her death.<\/p>\n
The answers that emerged from the analysis of her genome \u2014 and from the larger body of ancient American genomic research that the Upward Sun River findings fit into and helped reshape \u2014 are among the most significant developments in the study of human prehistory in the twenty-first century.<\/p>\n
This is the story of a small infant buried in a prehistoric hearth in Alaska, and of what her bones told the world about who the first Americans really were.<\/p>\n
The Landscape Above The Arctic Circle<\/p>\n
<\/p>\n
The Tanana River flows through the interior of Alaska, roughly a hundred miles southeast of Fairbanks, draining a broad valley between mountain ranges that define the middle of the state.<\/p>\n
The valley is subarctic \u2014 cold winters of genuine severity, summers short enough that the trees stay small and the ground never fully thaws, a landscape defined by spruce forests, river floodplains, wetlands, and the periodic drama of flood and fire that shape subarctic ecology.<\/p>\n
The Indigenous peoples of this region are the Athabascan-speaking nations \u2014 communities that have inhabited the Tanana Valley and its surrounding territory for thousands of years.<\/p>\n
Among them, the people who identify as Tanana Athabascans have the most direct historical connection to the landscape around the Upward Sun River site, which sits in their traditional territory.<\/p>\n
Their relationship to this land \u2014 and to the ancient people whose remains were found within it \u2014 would shape the terms under which the scientific research at Upward Sun River proceeded.<\/p>\n
The site itself is not dramatic in appearance.<\/p>\n
It occupies a low terrace above the Upward Sun River, a tributary of the Tanana.<\/p>\n
The terrace is the kind of location that prehistoric people chose repeatedly across North America and the rest of the world \u2014 elevated enough above the river to be protected from most floods, close enough to the water to have reliable access to fish and game, sheltered from the worst of the wind by the surrounding topography.<\/p>\n
Archaeological survey of the region had identified the site prior to the major excavations, and initial testing suggested the presence of cultural material at depths that indicated considerable age.<\/p>\n
Excavations led by Ben Potter of the University of Alaska Fairbanks began in earnest in the mid-2000s.<\/p>\n
Potter’s team worked systematically through the site’s stratigraphy \u2014 the layers of sediment that had accumulated over thousands of years \u2014 documenting the distribution and association of artifacts, animal bones, charcoal, and other materials that together built up a picture of human occupation through time.<\/p>\n
What the excavations found, over multiple seasons, was evidence of a campsite that had been used repeatedly during the late Pleistocene and early Holocene \u2014 the transition from the Ice Age to the modern geological epoch.<\/p>\n
People had camped here, processed game animals, made tools, and conducted the ordinary business of subsistence life in the subarctic.<\/p>\n
The animal bones recovered from the site documented a diet that included salmon, small mammals, and birds \u2014 the kinds of foods available in the Tanana Valley and that remain central to Indigenous subsistence economies in the region.<\/p>\n
<\/p>\n
The most significant find came in 2010 and 2013, when the excavation team uncovered the skeletal remains of two infants buried in what had been a hearth feature \u2014 a fire pit that had been used for cooking or warmth and that, at some point in the site’s history, had been repurposed as a burial location.<\/p>\n
The two infants would eventually be designated USR1 and USR2.<\/p>\n
Their discovery, and the scientific and ethical questions it raised, would transform Upward Sun River from a significant regional archaeological site into one of the most important locations in the study of early American prehistory.<\/p>\n
Two Infants In A Hearth<\/p>\n
The burial of very young children in or near hearths is not a practice unique to any single culture or time period.<\/p>\n
It appears in the archaeological record across the globe and across deep time, and while the specific beliefs and practices that motivated such burials varied enormously between cultures, the pattern itself speaks to something recognizable: the care that human communities invest in acknowledging the deaths of their youngest members, even when the practicalities of burial are constrained by season, location, or circumstance.<\/p>\n
<\/p>\n
At Upward Sun River, the hearth in which the infants were buried had been used as a cooking feature before the burials occurred.<\/p>\n
The transition from functional hearth to burial location \u2014 and the care with which the infants were placed within it \u2014 was clear from the archaeological evidence.<\/p>\n
The children were not randomly deposited or casually discarded.<\/p>\n
They were placed deliberately, in a specific configuration, in a location that had been part of the life of the people who buried them.<\/p>\n
USR1 was the more completely preserved of the two infants.<\/p>\n
Her skeletal remains were in sufficient condition to provide meaningful physical information and, crucially, to yield usable ancient DNA.<\/p>\n
<\/p>\n
She was a female, estimated at the time of analysis to have been somewhere between six weeks and about three months old at the time of her death \u2014 an infant in the earliest period of life, too young to have accumulated much experience of the world but old enough to have been known and mourned by the community she had briefly been part of.<\/p>\n
USR2 was in worse condition \u2014 the preservation of the skeletal material was poorer, and the remains were more fragmentary.<\/p>\n
A third set of remains was eventually identified through analysis of the burial context, possibly representing a fetus.<\/p>\n
The specifics of USR2’s analysis have been less completely published than those of USR1, partly because the material was less amenable to the kinds of genetic analysis that proved so powerful in USR1’s case.<\/p>\n
The radiocarbon dates obtained from the USR1 burial placed it at approximately 11,500 years before the present.<\/p>\n
<\/p>\n
This date, which would be refined through subsequent work, made the Upward Sun River infants among the oldest human remains found in Alaska and among the earliest from anywhere in North America that have yielded recoverable ancient DNA.<\/p>\n
The implications of that date extended well beyond Alaskan archaeology.<\/p>\n
At 11,500 years ago, the last Ice Age had recently ended.<\/p>\n
The ice sheets that had covered much of North America were in retreat, though residual glaciation remained in many areas.<\/p>\n
The Bering land bridge \u2014 the broad land connection between northeastern Asia and Alaska that had been exposed during the lowered sea levels of the glacial maximum \u2014 was in the process of being submerged as sea levels rose.<\/p>\n
The landscape of Alaska was in rapid ecological transition, with the cold, dry steppe-tundra of the late Pleistocene giving way to the wetter, more forested conditions of the Holocene.<\/p>\n
<\/p>\n
The people who lived at Upward Sun River 11,500 years ago were living at the end of the world they had known \u2014 or at the beginning of a new one, depending on how one frames the transition from Ice Age to post-glacial.<\/p>\n
They were among the earliest well-documented inhabitants of the interior of North America north of the ice, navigating a landscape that was changing around them with a speed that, measured in ecological time, was rapid and disorienting.<\/p>\n
They buried their dead with care.<\/p>\n
Why The Site Already Mattered<\/p>\n
Before the genome of USR1 was sequenced, before the term Ancient Beringian was coined, before the 2018 Nature paper that would make Upward Sun River globally significant in the study of ancient Americans \u2014 the site already mattered for reasons that were entirely archaeological.<\/p>\n
One of the persistent problems in the study of the earliest Americans is the scarcity of well-preserved, well-documented sites from the critical period of initial peopling and early post-colonization spread.<\/p>\n
<\/p>\n
Most early sites are known primarily from stone tools \u2014 durable objects that survive the thousands of years that separate us from the earliest Americans, but that provide limited information about the people who made and used them.<\/p>\n
Sites that preserve organic material \u2014 bone, charcoal, plant material \u2014 allow for radiocarbon dating and dietary analysis that stone tools alone cannot provide.<\/p>\n
Sites that preserve human skeletal remains are rarer still, and sites that preserve human skeletal remains in burial context, with clear documentation of the spatial and stratigraphic relationships that define the burial, are genuinely exceptional.<\/p>\n
Upward Sun River was exceptional in all of these respects.<\/p>\n
The site preserved animal bones in good enough condition for dietary analysis.<\/p>\n
<\/p>\n
The charcoal from the hearth features provided high-quality radiocarbon dates.<\/p>\n
And the infant burials, documented with the systematic care that Ben Potter’s team brought to the excavation, preserved not just the skeletal remains themselves but the context that made those remains interpretable.<\/p>\n
The animal bones associated with the site’s occupation horizons told a story about the diet and subsistence strategies of the people who had camped there repeatedly over the late Pleistocene and early Holocene.<\/p>\n
Salmon bones indicated that the river had been fished \u2014 that the people at the site had access to and were using the fish runs that remain a defining feature of Alaskan subsistence economies.<\/p>\n
<\/p>\n
Small mammal bones and bird bones added to the dietary picture.<\/p>\n
The presence of stone tools in styles consistent with the regional archaeological tradition of the late Pleistocene allowed the site to be placed within the broader framework of Alaskan and subarctic prehistory.<\/p>\n
The hearth features themselves were informative.<\/p>\n
The site showed evidence of repeated use \u2014 people had returned to this location multiple times over a period of years or decades or longer, using it as a base camp from which to exploit the surrounding landscape’s resources.<\/p>\n
The repeated use of a specific location implies a community’s knowledge of that landscape and a pattern of seasonal or opportunistic return that is characteristic of mobile hunter-gatherer groups in productive but challenging environments.<\/p>\n
<\/p>\n
The burial of the infants within a former cooking hearth added another dimension to this picture.<\/p>\n
The choice of that location \u2014 a place that had been central to the life and warmth of the camp \u2014 for the burial of the community’s youngest members speaks to relationships between the living and the dead that we can recognize as human even if we cannot know the specific cultural logic that motivated the choice.<\/p>\n
All of this made Upward Sun River a site of considerable archaeological significance before anyone had sequenced a single base pair of ancient DNA from it.<\/p>\n
The DNA would not change the archaeological findings.<\/p>\n
<\/p>\n
It would add a completely different and revolutionary layer of information to a picture that was already extraordinarily rich by the standards of early American archaeology.<\/p>\n
Why Ancient DNA Is So Hard<\/p>\n
To understand what the sequencing of USR1’s genome accomplished, it helps to understand how difficult the process is and why ancient DNA from Arctic sites is both more and less tractable than ancient DNA from other environments.<\/p>\n
DNA is an unstable molecule.<\/p>\n
After an organism dies, the DNA in its cells begins to fragment and chemically degrade.<\/p>\n
Bacteria colonize the remains and begin to break down organic material, including DNA.<\/p>\n
<\/p>\n
The specific chemistry of the burial environment determines how quickly and how thoroughly this degradation occurs.<\/p>\n
Cold, dry conditions slow degradation.<\/p>\n
The permafrost and near-permafrost conditions of subarctic Alaska \u2014 where ground temperatures remain low even in summer and where frozen ground can preserve organic material for thousands of years \u2014 might seem ideal for ancient DNA preservation.<\/p>\n
And in some respects they are: many extraordinary ancient specimens have been recovered from permafrost across Siberia and Alaska, including woolly mammoths with intact hair, skin, and even stomach contents.<\/p>\n
But human skeletal material presents specific challenges.<\/p>\n
<\/p>\n
The bones of humans are less dense than those of large mammals, and they are more readily affected by the freeze-thaw cycles that occur at the margins of permafrost zones.<\/p>\n
Repeated freezing and thawing physically damages bone structure and accelerates the chemical processes that degrade DNA.<\/p>\n
The specific burial conditions at Upward Sun River \u2014 including the depth of burial, the surrounding sediment matrix, and the specific temperature regime experienced by the remains over eleven and a half thousand years \u2014 would determine whether usable ancient DNA had survived.<\/p>\n
The answer, for USR1, was a qualified yes.<\/p>\n
The skeletal material preserved ancient DNA, but the preservation was imperfect.<\/p>\n
<\/p>\n
The DNA was fragmented \u2014 broken into short pieces, as ancient DNA always is \u2014 and chemically damaged, with the specific patterns of deamination (a chemical alteration that affects cytosine bases) that are characteristic of authentic ancient DNA and that laboratory methods are specifically designed to detect and accommodate.<\/p>\n
The research team that conducted the genome analysis worked at the Centre for GeoGenetics at the University of Copenhagen, the same institution associated with Eske Willerslev and his colleagues who had been central to several other landmark ancient American DNA studies.<\/p>\n
The analysis used the next-generation sequencing methods that had transformed the field over the preceding decade, combined with the sophisticated computational approaches for filtering contamination, correcting for damage patterns, and assembling coherent genomic sequences from millions of short, degraded fragments.<\/p>\n
The genome they obtained from USR1 was not perfect.<\/p>\n
<\/p>\n
It did not have the coverage depth of a modern genome sequenced from a fresh sample.<\/p>\n
But it was complete enough \u2014 with sufficient coverage of the genome to allow reliable population genetic comparisons \u2014 to address the fundamental questions about where this child fit in the family tree of ancient and modern human populations.<\/p>\n
What the analysis revealed was unexpected enough that the researchers checked their methods carefully before accepting the conclusion.<\/p>\n
The Genome Speaks<\/p>\n
When the population genetic analysis of the USR1 genome was completed and the results were compared against the growing library of ancient and modern human genomes from around the world, the statistical relationships were clear.<\/p>\n
USR1 was most closely related to Native American populations.<\/p>\n
<\/p>\n
This was the first and most fundamental result, and it established that whatever else the analysis would show about the child’s specific ancestry, she was unambiguously part of the founding population of the Americas \u2014 the population that had migrated from northeastern Asia during the Ice Age and eventually gave rise to all of the Indigenous peoples of the Western Hemisphere.<\/p>\n
This was important to establish clearly, because the morphological diversity of early American populations \u2014 the variation in skull shape that had led some researchers to propose multiple founding migrations \u2014 had created a scientific and sometimes politically charged context in which any finding that placed an early American outside the mainstream of later Native American populations could be misinterpreted or misused.<\/p>\n
USR1’s relationship to Native American populations was unambiguous: she was more closely related to Native Americans than to any non-American population.<\/p>\n
But the analysis also showed that within the broad category of Native American-related populations, USR1 occupied a specific and unusual position.<\/p>\n
<\/p>\n
When researchers examined the genetic distances between USR1 and the various ancient and modern Native American genomes available for comparison, they found that she was more distantly related to all of them than those populations were to each other.<\/p>\n
In population genetic terminology, she was basal to the sampled Native American populations.<\/p>\n
This means that in the family tree of Native American populations \u2014 the branching diagram that shows how different groups relate to each other and to their common ancestors \u2014 USR1 sat closer to the root of the tree than any previously sampled population.<\/p>\n
She belonged to a lineage that diverged from the ancestors of other Native American populations before those populations began to differentiate from each other.<\/p>\n
The researchers who published the 2018 Nature paper on USR1 \u2014 Moreno-Mayar and colleagues \u2014 described the lineage she represented as Ancient Beringians.<\/p>\n
<\/p>\n
The name was chosen to reflect both the geographic context (Beringia, the region connecting Asia and North America during the Ice Age) and the temporal position (ancient, in the sense of belonging to the deepest sampled stratum of Native American ancestry).<\/p>\n
The term Ancient Beringian is a scientific label, not a cultural designation.<\/p>\n
It describes a specific genetic lineage inferred from population genetic analysis.<\/p>\n
It does not refer to a named historical people, a documented cultural tradition, or a community that identified itself by any particular name.<\/p>\n
It is the name that science gave to a statistical relationship \u2014 the relationship between USR1 and the populations that descended from the same founding stock but through a different branch.<\/p>\n
Understanding what Ancient Beringian means \u2014 and what it does not mean \u2014 is essential to understanding what the USR1 genome actually revealed.<\/p>\n
<\/p>\n
What Basal Really Means<\/p>\n
The word basal is one of the most important terms in the USR1 story, and it is also one of the most easily misunderstood.<\/p>\n
In a phylogenetic tree \u2014 a branching diagram that represents the evolutionary or population genetic relationships between groups \u2014 basal means closer to the root.<\/p>\n
When researchers say that USR1 is basal to other Native American populations, they mean that in the family tree of Native Americans, the branch leading to USR1’s lineage diverged before the branches leading to other sampled populations.<\/p>\n
This does not mean that USR1 represents an older or more primitive form of humanity.<\/p>\n
<\/p>\n
It does not mean that her lineage was unchanged from the ancestral founding population while other populations evolved.<\/p>\n
It does not mean that she is the ancestor of all other Native Americans or that her lineage is in any way superior, inferior, or more authentic than other Native American lineages.<\/p>\n
It means something much more specific and much more modest: that when the founding population of the Americas began to differentiate into distinct subpopulations, the lineage leading to USR1 was one of the first to diverge, and the populations sampled for comparison had diversified further after that initial divergence.<\/p>\n
To make this concrete, imagine the founding population of the Americas as a single ancestral group.<\/p>\n
<\/p>\n
Over time, this group \u2014 spread across a large area and subject to the ordinary processes of isolation and genetic drift \u2014 begins to differentiate.<\/p>\n
One branch separates and continues along a distinct trajectory.<\/p>\n
The remaining population continues to differentiate, eventually producing the various lineages that we associate with North and South American Indigenous populations.<\/p>\n
Under the model proposed in the 2018 paper, the lineage leading to USR1 was one of the early branches \u2014 perhaps the earliest well-documented one.<\/p>\n
The fact that it diverged before other sampled populations does not make it the ancestor of those populations.<\/p>\n
It makes it a sister lineage \u2014 a branch that shares a common ancestor with the other branches but that represents a distinct trajectory from the point of divergence.<\/p>\n
<\/p>\n
The analogy to human family structures is imperfect, as all analogies in population genetics are, but it may help: USR1 is not the mother of other Native American lineages.<\/p>\n
She is more like a very distant great-aunt \u2014 someone who shares the same great-grandparent as all the others but who belongs to a branch of the family that went in a different direction from the others very early on.<\/p>\n
The branching that created the Ancient Beringian lineage appears, based on the demographic modeling in the 2018 paper, to have occurred at a specific and significant point in time: approximately 20,000 years ago.<\/p>\n
This date \u2014 rough, uncertain, carrying the standard uncertainty of population genetic estimates \u2014 placed the divergence of the Ancient Beringian lineage well before the arrival of the founding population in the Americas in the conventional sense, and approximately at the period that other lines of evidence associate with the Beringian standstill.<\/p>\n
<\/p>\n
The Beringian Standstill<\/p>\n
The Beringian standstill hypothesis is one of the most important and most discussed models in the study of the first Americans.<\/p>\n
Understanding it is essential to understanding what the USR1 genome revealed.<\/p>\n
During the Last Glacial Maximum \u2014 roughly 26,000 to 19,000 years ago \u2014 the ice sheets that covered much of North America were at their greatest extent.<\/p>\n
The Laurentide Ice Sheet reached from the Arctic to the northern United States.<\/p>\n
The Cordilleran Ice Sheet covered the western mountain ranges.<\/p>\n
<\/p>\n
Together, they formed a virtually impassable barrier across the northern part of the continent.<\/p>\n
At the same time, the land connection between Siberia and Alaska \u2014 Beringia \u2014 was wide open.<\/p>\n
Sea levels were much lower than today because so much of the world’s water was locked up in ice.<\/p>\n
The land bridge was not a narrow corridor but a broad, flat, vegetated landmass extending hundreds of miles from north to south.<\/p>\n
It was inhabited by large mammals \u2014 mammoths, horses, bison \u2014 and, according to the standstill hypothesis, by people.<\/p>\n
The standstill hypothesis proposes that the founding population of the Americas \u2014 the ancestral group that would eventually give rise to all Native American peoples \u2014 was present in Beringia during the Last Glacial Maximum but could not move south because of the ice sheets.<\/p>\n
<\/p>\n
For a period of perhaps several thousand years, this population was isolated in Beringia, accumulating genetic changes specific to the isolated population while the rest of the world continued to evolve along different trajectories.<\/p>\n
The genetic signature of this isolation \u2014 the specific pattern of genetic differentiation that accumulated during the standstill period \u2014 is reflected in the distinctive genetic makeup of Native American populations.<\/p>\n
Native Americans are more closely related to northeastern Asian populations than to any other non-American group, but they differ from those Asian populations in specific ways that reflect the genetic changes that occurred during the period of Beringian isolation.<\/p>\n
The standstill model proposes that these differences accumulated over the thousands of years when the founding population was isolated in Beringia before moving south.<\/p>\n
<\/p>\n
The demographic modeling associated with the USR1 analysis supports a picture consistent with the standstill hypothesis.<\/p>\n
The estimated date of divergence between the Ancient Beringian lineage and the ancestors of other Native American populations \u2014 around 20,000 years ago \u2014 is consistent with a split that occurred during the standstill period, before the southward expansion that would eventually populate the rest of the hemisphere.<\/p>\n
The simplest interpretation \u2014 the one that the 2018 paper proposed and that subsequent research has generally supported \u2014 is that the founding population of the Americas was present in Beringia during the glacial maximum, and that during this period, the population began to differentiate into at least two subgroups.<\/p>\n
One subgroup \u2014 the one that USR1 belonged to \u2014 remained in or near Beringia and eventually populated parts of Alaska and possibly adjacent areas.<\/p>\n
<\/p>\n
The other subgroup moved south as the ice retreated, eventually spreading through North America and into South America with the rapid geographic expansion that the archaeological and genetic evidence documents.<\/p>\n
What happened to the Ancient Beringian lineage \u2014 why USR1’s specific genetic profile is not clearly recognizable in modern populations \u2014 is one of the most interesting questions the discovery raised.<\/p>\n
Beringia As Homeland, Not Just Highway<\/p>\n
Much of the popular understanding of Beringia treats it as a transit zone \u2014 a land bridge that people crossed in order to reach the Americas.<\/p>\n
This framing is geographically and intellectually limiting, because it treats the land connection itself as empty or unimportant except as a path between two more significant places.<\/p>\n
<\/p>\n
The evidence from the genetics and the archaeology increasingly argues for a different understanding: Beringia was a homeland.<\/p>\n
For thousands of years during the Last Glacial Maximum, the broad expanse of land connecting Asia and North America was not just a throughway but a place \u2014 a productive, inhabited landscape where people lived for many generations, developing the specific cultural adaptations and genetic distinctiveness that characterize the founding population of the Americas.<\/p>\n
The ecology of Beringia during the Last Glacial Maximum was not what it might seem from a modern perspective.<\/p>\n
The central and eastern portions of Beringia that are now submerged under the Bering and Chukchi Seas were then dry land covered by vegetation \u2014 not the barren tundra of the modern Siberian and Alaskan coasts, but a productive steppe-tundra ecosystem that supported dense populations of large herbivores.<\/p>\n
<\/p>\n
Woolly mammoths, woolly rhinoceroses, bison, horses, and other megafauna grazed across this landscape.<\/p>\n
Predators \u2014 wolves, cave lions \u2014 followed the herds.<\/p>\n
And people followed the predators and the herds, living in a landscape that, while cold and demanding, was far from empty.<\/p>\n
The genetic evidence for the Beringian standstill \u2014 the period of population isolation that the demographic modeling implies \u2014 suggests that the founding population of the Americas spent an extended period in this homeland before the southward expansion began.<\/p>\n
The specific genetic signature that distinguishes Native Americans from their closest northeastern Asian relatives is the product of this isolation.<\/p>\n
<\/p>\n
New mutations accumulated during the standstill.<\/p>\n
Genetic variants that were present in the wider Asian population but were absent from the Beringian founding population were lost by genetic drift.<\/p>\n
Allele frequencies shifted in directions specific to the isolated population.<\/p>\n
The result was a founding population that was genetically distinct from the Asian populations it had originally been part of \u2014 distinct enough to be recognizable as specifically American in population genetic terms, even when we are comparing genomes from people who lived eleven thousand years ago.<\/p>\n
The Ancient Beringian lineage \u2014 the branch that USR1 belonged to \u2014 apparently remained in or near the Beringian homeland for an extended period, while the ancestors of most other Native Americans moved south through the ice-free corridors and coastal routes that became available as the glaciers retreated.<\/p>\n
<\/p>\n
What this means in practical terms \u2014 what the daily life of the Ancient Beringian people looked like, what territory they occupied, how they related to the people who eventually moved south \u2014 is not recoverable from a single genome.<\/p>\n
But the genetic evidence establishes that the split between USR1’s lineage and the ancestors of other sampled Native American populations occurred before the southward expansion and appears to have maintained a geographic footprint that was distinct from the populations that eventually populated the rest of the hemisphere.<\/p>\n
This is Beringia as homeland: not just a place people passed through, but a place where a distinct human population lived for long enough to develop its own genetic character \u2014 and where that character was preserved in the genome of a tiny infant buried in a hearth in Alaska eleven and a half thousand years ago.<\/p>\n
The First Major Model \u2014 And Why It Was Not The End Of The Story<\/p>\n
<\/p>\n
The 2018 Moreno-Mayar paper proposed a specific demographic model for the founding of the Americas based on the USR1 genome and comparison with previously published ancient and modern genomes.<\/p>\n
The model had several key components.<\/p>\n
First, it proposed that the founding population of the Americas \u2014 the group that entered the hemisphere from Beringia and eventually gave rise to all Native American populations \u2014 was a single founding population, not multiple independent founding groups.<\/p>\n
The diversity within the founding population, the model suggested, reflected differentiation that occurred within a single population that had been isolated in Beringia during the standstill period.<\/p>\n
Second, within this founding population, the model identified two main branches.<\/p>\n
<\/p>\n
One branch led to the Ancient Beringians \u2014 the lineage represented by USR1, which remained in or near the Beringian region.<\/p>\n
The other branch gave rise to what the paper called the “First Americans” \u2014 the ancestral population of most contemporary and ancient Native Americans sampled, which expanded southward as the ice retreated.<\/p>\n
Third, the model placed the divergence between these two branches at approximately 20,000 years before the present \u2014 consistent with the standstill period, before the southward expansion of the First American branch began.<\/p>\n
This model was not derived from the USR1 genome alone.<\/p>\n
<\/p>\n
It was the result of comparing USR1 to the other genomes available in 2018 and finding the model that best fitted the observed pattern of genetic relationships.<\/p>\n
The model was a hypothesis, not a certainty \u2014 it was the most parsimonious explanation of the available data, subject to revision as additional data became available.<\/p>\n
And revision, in the years since the 2018 paper, is exactly what happened.<\/p>\n
Not revision in the sense of the core findings being overturned \u2014 USR1’s position as basal to other sampled Native American populations and her classification as representing a previously unsampled ancient lineage have been robustly confirmed by subsequent research.<\/p>\n
But revision in the sense of increasing complexity and increasing uncertainty about the specific demographic history that produced the observed genetic patterns.<\/p>\n
<\/p>\n
The picture of the founding of the Americas that emerged in subsequent years \u2014 from additional ancient genomes, from improved demographic modeling methods, from the analysis of modern Native American genomes with greater depth and breadth than had been possible in 2018 \u2014 was more complex than the simple two-branch model suggested.<\/p>\n
The founding of the Americas, it increasingly appeared, involved not just one split but multiple splits, at different times, producing a pattern of population differentiation that is still being mapped with growing precision.<\/p>\n
The Northern And Southern Branches<\/p>\n
One of the most important findings to emerge from the broader body of ancient American genomics \u2014 supported by the USR1 analysis and by subsequent research \u2014 was the identification of two major branches within the main Native American founding population: the ancestors of Indigenous peoples in northern North America and the ancestors of Indigenous peoples in southern North America and South America.<\/p>\n
This north-south split was not a new idea in 2018, but the USR1 analysis contributed to its characterization and to the modeling of when it occurred.<\/p>\n
<\/p>\n
The two branches appear to have diverged relatively early in the history of the post-Beringian expansion \u2014 possibly before the spread of Clovis technology, and possibly before the main southward expansion had reached its greatest geographic extent.<\/p>\n
The northern branch is represented, in the ancient genomic record, by populations ancestral to many of the Indigenous peoples of the Arctic, Subarctic, and northern portions of the continent.<\/p>\n
The southern branch is represented by the Anzick-1 genome from Montana \u2014 the Clovis-period child whose genome showed a stronger affinity with populations from Central and South America than with those from northern North America.<\/p>\n
The USR1 genome \u2014 the Ancient Beringian lineage \u2014 sits outside this north-south split, representing a divergence that preceded the split between northern and southern branches.<\/p>\n
<\/p>\n
This structural position in the family tree is what makes USR1 so important as a data point for modeling the founding of the Americas.<\/p>\n
She provides information about the state of the founding population before the main diversification events that produced the north-south distinction, giving researchers a reference point for the deep ancestry that all Native Americans share.<\/p>\n
The north-south split, and the Ancient Beringian divergence that preceded it, together sketch a picture of the founding of the Americas as a multi-stage process: first, a period of isolation in Beringia that produced the founding population and began the process of differentiation; then, a divergence between the Ancient Beringian lineage and the ancestors of other Native Americans; then, a divergence within the main Native American ancestral population that produced the northern and southern branches; then, the geographic expansion of those branches through the hemisphere.<\/p>\n
Each stage of this process took time \u2014 time measured in thousands of years \u2014 and each stage was shaped by the specific geography, ecology, and demographic history of the populations involved.<\/p>\n
<\/p>\n
The Americas were not populated in a single generation or even a single century.<\/p>\n
They were populated over millennia, through a process of gradual expansion and differentiation that built up the human diversity of the hemisphere layer by layer.<\/p>\n
What Happened To The Ancient Beringians<\/p>\n
One of the most intriguing questions raised by the USR1 discovery is what became of the Ancient Beringian lineage.<\/p>\n
If a distinct genetic branch diverged from the main Native American founding population approximately 20,000 years ago and maintained a distinct identity long enough to be preserved in the genome of an 11,500-year-old infant in Alaska, where is that lineage in the modern genetic record?<\/p>\n
The honest answer is that it is not clearly identifiable.<\/p>\n
<\/p>\n
No modern Indigenous American population has been shown to carry a clear and unambiguous signal of exclusively Ancient Beringian ancestry.<\/p>\n
The lineage appears, in the current genetic data, to have either gone extinct, to have been absorbed into other populations through admixture, or to have persisted in forms that are not easily distinguishable from the admixed genetic backgrounds of modern populations.<\/p>\n
The most likely explanation, given what the genetic data shows, is admixture \u2014 the mixing of the Ancient Beringian lineage with the populations that expanded northward from the south as the climate warmed and human populations grew.<\/p>\n
The fossil genetic record from Alaska and adjacent areas from the period after USR1 shows a shift toward the genetic profiles associated with the main Native American branches \u2014 a shift that suggests the Ancient Beringian lineage was gradually diluted through mixing with populations moving in from the south.<\/p>\n
<\/p>\n
This process \u2014 of a distinct genetic lineage being absorbed into a larger, expanding population through admixture \u2014 is not unusual in population genetic history.<\/p>\n
It has occurred in many parts of the world, and the genomic traces of absorbed populations can often be detected in the admixed descendants as subtle but statistically identifiable signals.<\/p>\n
Researchers studying modern Indigenous Alaskan and subarctic populations have found some evidence of Ancient Beringian-like ancestry signals in certain populations, but the evidence is not strong enough to clearly identify any specific modern community as primarily descended from the Ancient Beringian lineage.<\/p>\n
The question of extinction versus absorption is not merely academic.<\/p>\n
<\/p>\n
If the Ancient Beringian lineage went entirely extinct \u2014 if the people who represented this distinct early American branch died out without any descendants \u2014 then USR1’s genome is the only direct evidence of their existence.<\/p>\n
If they were absorbed through admixture, then their genetic legacy is distributed, in diluted form, among the descendants of the populations that mixed with them.<\/p>\n
Current evidence cannot definitively distinguish between these possibilities, and subsequent ancient DNA studies from Alaska and adjacent areas will be important in characterizing what happened to the Ancient Beringian lineage in the millennia after USR1 lived.<\/p>\n
What can be said is that the Ancient Beringian lineage was real, was distinct, and persisted long enough \u2014 at least until 11,500 years ago \u2014 to be preserved in the genome of a child buried in the interior of Alaska.<\/p>\n
<\/p>\n
Beyond that, the genetic record is currently silent.<\/p>\n
The Ethics Of The Infant’s Genome<\/p>\n
Before the genome of USR1 could be analyzed, and before any publication could proceed, a set of ethical questions had to be addressed \u2014 questions that were particularly acute because the remains were those of an infant, recovered from the traditional territory of living Athabascan communities who had an obvious and direct interest in how those remains were treated.<\/p>\n
The regulatory framework governing the treatment of ancient Native American remains in Alaska is complex.<\/p>\n
<\/p>\n
The Native American Graves Protection and Repatriation Act (NAGPRA) applies on federal lands and to federally funded institutions, but its application to ancient remains from archaeological sites \u2014 particularly remains old enough that cultural affiliation with any specific modern tribe cannot be established under the law’s standards \u2014 has been a source of ongoing legal and ethical debate.<\/p>\n
The Upward Sun River site was excavated under permits from the relevant federal and state authorities.<\/p>\n
The Native communities with traditional territory at and around the site \u2014 primarily Athabascan-speaking nations with historical and cultural connections to the Tanana Valley \u2014 were consulted as part of the research process.<\/p>\n
The nature and extent of those consultations, and the specific concerns and perspectives that community representatives brought to them, shaped the way the research was conducted and the way the findings were communicated.<\/p>\n
Ben Potter and his colleagues have described the consultation process as ongoing and respectful, with community members participating in discussions about the significance of the findings and the appropriate ways to communicate them publicly.<\/p>\n
<\/p>\n
The Healy Lake Village Council and other Athabascan community representatives were engaged with the research, and some have expressed views about the significance of the USR1 findings that reflect Indigenous understandings of ancestry and historical presence that align with \u2014 though are not reducible to \u2014 the scientific findings.<\/p>\n
The specific question of whether and how to conduct invasive analysis on the remains of very young children \u2014 infants who had not yet developed a social identity in the community and whose lives were brief enough that their individual personhood raises particular ethical sensitivities \u2014 was addressed within the consultation framework.<\/p>\n
The decision to proceed with genetic analysis was made within a process that included Indigenous participation, though the degree to which that participation constituted genuine informed consent by the affected communities is a question that Indigenous scholars continue to discuss.<\/p>\n
The broader ethics of ancient DNA research on Indigenous remains \u2014 questions about who controls the data, who benefits from the findings, what happens to the genetic information after analysis, and how Indigenous communities can meaningfully participate in decisions about research on their ancestors \u2014 are actively discussed in the scientific community and in Indigenous scholarship.<\/p>\n
<\/p>\n
The Upward Sun River project was conducted within a framework that, by the standards of its time, represented genuine engagement with these questions.<\/p>\n
Whether that framework was sufficient, or whether more could and should have been done, is a judgment that belongs partly to the communities most directly affected.<\/p>\n
What the research community can say is that the findings from USR1 have been communicated publicly in ways that have been broadly welcomed by many Indigenous scholars and community members, partly because those findings specifically undercut the kinds of claims about multiple founding populations and non-Native early Americans that have sometimes been used to complicate Indigenous rights arguments.<\/p>\n
Why Eleven Thousand Years Is Not The Oldest<\/p>\n
<\/p>\n
The age of the USR1 burial \u2014 approximately 11,500 years before the present \u2014 is often presented as placing the Upward Sun River infant among the very earliest Americans.<\/p>\n
This is accurate in a specific sense: she is among the oldest Americans whose remains have been recovered and whose genome has been successfully analyzed.<\/p>\n
But it is important to understand that 11,500 years is not close to the actual beginning of human presence in the Americas.<\/p>\n
The evidence for human presence in the Americas before 11,500 years ago is now extensive and comes from multiple independent lines of inquiry.<\/p>\n
The footprints at White Sands National Park in New Mexico \u2014 dated by multiple independent methods to approximately 21,000 to 23,000 years before the present \u2014 represent the most dramatic physical evidence of human presence during the Last Glacial Maximum.<\/p>\n
<\/p>\n
If those dates are correct, people were in the interior of North America more than ten thousand years before USR1 was born.<\/p>\n
The Monte Verde site in Chile, with well-documented occupation dating to approximately 14,500 to 15,000 years before the present, demonstrates that people had spread to the southern tip of South America well before the Clovis period \u2014 which itself predates the Upward Sun River burial by at least a thousand years.<\/p>\n
The Anzick burial in Montana, dated to approximately 12,600 years before the present, preserves the remains of a Clovis-period child whose genome has been analyzed and whose genetic profile shows the characteristics of the main Native American founding population.<\/p>\n
USR1 at 11,500 years is not the oldest evidence of Americans.<\/p>\n
<\/p>\n
She is, among the oldest Americans whose genome has been analyzed, one of the most important \u2014 but her importance derives from what her genome shows, not from the date alone.<\/p>\n
The combination of her age (old enough to be informative about the founding period), her location (Alaska, near the Beringian source region), and her genetic profile (basal to other sampled Native American populations) is what makes her remarkable.<\/p>\n
Understanding that USR1 existed well after the initial peopling of the Americas is important for interpreting what her genome tells us.<\/p>\n
She was not among the very first people in the Americas.<\/p>\n
She was a member of a lineage that had already diverged from other lineages some ten thousand years before her birth \u2014 a lineage that had maintained its distinct genetic character through the intervening period, in a region where the specific ecology and the specific history of the founding population’s differentiation had allowed that distinctiveness to persist.<\/p>\n
<\/p>\n
This is a story about a specific branch of an ancient family \u2014 not about the very beginning of the family, but about a branch that preserved the deepest-sitting genetic characteristics of the founding lineage that we have been able to directly observe.<\/p>\n
The Archaeology Beyond The DNA<\/p>\n
The genome of USR1 was the most globally significant finding from Upward Sun River, but the archaeology of the site \u2014 independent of the genetic analysis \u2014 has contributed substantially to the understanding of how people lived in interior Alaska during the late Pleistocene and early Holocene.<\/p>\n
The dietary evidence from the site is particularly informative.<\/p>\n
The combination of salmon bones, small mammal bones, and bird remains in the occupation horizons documents a subsistence strategy that combined fishing with hunting and gathering \u2014 a pattern that is recognizable in the historical and contemporary practices of Athabascan communities in the region and that reflects the specific productivity of subarctic river systems.<\/p>\n
The salmon run that provides the modern Tanana Valley with its most productive seasonal food resource was apparently already being exploited by people 11,500 years ago.<\/p>\n
<\/p>\n
This is significant for understanding the ecology of the early Holocene in interior Alaska and for understanding how the people of this period structured their annual round of resource exploitation.<\/p>\n
Salmon are available in enormous quantities during the run season but require processing and storage to sustain a community through the non-run period.<\/p>\n
The presence of salmon bones at Upward Sun River suggests that the people who camped there had either the capability to process and store salmon or were visiting the site specifically during the run season.<\/p>\n
The stone tools recovered from the site have been analyzed within the framework of Alaskan archaeological traditions, contributing to the understanding of the technological practices of the people who lived in the region during the period of transition from late Pleistocene to early Holocene.<\/p>\n
The specific tool types and manufacturing techniques present at Upward Sun River are being compared to those from other contemporaneous sites across interior Alaska and the broader subarctic, building a picture of the technological variation and cultural connections across the region during this period.<\/p>\n
<\/p>\n
The repeated use of the site \u2014 the evidence for multiple occupations at different levels within the stratigraphic sequence \u2014 documents a pattern of place use that speaks to the kind of landscape knowledge and seasonal planning that characterizes mobile hunter-gatherer groups in productive environments.<\/p>\n
Returning to a known, productive site is both a practical and a cognitive act: it requires memory of where good resources are, planning for when to be in a particular place, and the social organization needed to coordinate group movement across a landscape.<\/p>\n
These behavioral dimensions of the Upward Sun River evidence are not captured by the genome.<\/p>\n
They are captured by the archaeological record \u2014 by the bones and tools and charcoal and structural evidence of occupation that the excavation team documented with careful precision over multiple field seasons.<\/p>\n
The genome and the archaeology together tell a richer story than either could tell alone.<\/p>\n
<\/p>\n
The Problem With Statistical Populations<\/p>\n
One of the most important caveats that both researchers and journalists need to observe when discussing findings like those from USR1 is the distinction between a statistical population in the sense used by geneticists and an actual historical people \u2014 a specific community with a specific culture, language, territory, and identity.<\/p>\n
When population geneticists refer to the Ancient Beringians, they are referring to a statistical construct: a genetic lineage inferred from the patterns in one genome and from comparison with other available genomes.<\/p>\n
The label describes where USR1’s lineage sits in a mathematical model of population relationships.<\/p>\n
<\/p>\n
It does not describe a specific historical community that called itself Ancient Beringian, that had a specific language, that had a specific territory or ceremonial tradition or political organization.<\/p>\n
The founding population of the Americas, as described in the genetic literature, is similarly a statistical construct \u2014 an inferred ancestral population that is postulated because it is the best-fitting ancestor for the observed diversity of Native American genomes.<\/p>\n
The founding population did not call itself that.<\/p>\n
It was not a single community in the social sense.<\/p>\n
It was a collection of people who were related to each other more closely than to other human populations and who, together, represent the demographic source from which all later Native American populations descended.<\/p>\n
This distinction matters for several reasons.<\/p>\n
<\/p>\n
First, it prevents the misinterpretation of population genetic findings as direct evidence about the history of specific, named communities.<\/p>\n
The genome of USR1 tells us about the genetic lineage to which she belonged and about the broad population history of the Americas.<\/p>\n
It does not tell us anything directly about the history of any specific Native nation \u2014 not the Athabascan nations with traditional territory at Upward Sun River, not the Clovis people, not any specific contemporary community.<\/p>\n
Second, it prevents the inappropriate use of genetic findings to make claims about cultural continuity or discontinuity.<\/p>\n
Population genetics can tell us about the movement and differentiation of human populations as measured by genetic markers.<\/p>\n
<\/p>\n
It cannot tell us directly about the movement and differentiation of cultures, languages, or political identities, all of which can change more rapidly and by different mechanisms than genetic profiles.<\/p>\n
Third, it supports the recognition that living Indigenous communities are not simply the biological outcomes of ancient population processes.<\/p>\n
They are communities with their own histories, their own forms of self-knowledge, and their own accounts of who they are and where they come from \u2014 accounts that deserve to be taken seriously on their own terms, not just as data to be checked against the findings of population genetics.<\/p>\n
The Ancient Beringians were real, in the specific sense that USR1 represents a real genetic lineage that diverged from other Native American lineages at a specific point in the past.<\/p>\n
<\/p>\n
They were not a specific historical people in the sense of a named, self-identified community with a particular cultural tradition.<\/p>\n
The distinction is between a scientific inference and a historical reality \u2014 and both can be true simultaneously without contradiction.<\/p>\n
Later Genomes And Refinements<\/p>\n
The 2018 USR1 paper was not the last word on the Ancient Beringian lineage or on the founding of the Americas.<\/p>\n
In the years since its publication, the accumulating body of ancient American genomic data has refined, complicated, and in some cases revised aspects of the picture that the Moreno-Mayar paper proposed.<\/p>\n
One of the most significant developments has been the analysis of ancient genomes from other early American sites, which has added additional data points for modeling the early diversification of the founding population.<\/p>\n
<\/p>\n
Each new ancient genome contributes either additional support for the existing model or new constraints that force revision.<\/p>\n
Genomes from sites in Siberia and northeastern Asia have been particularly important for understanding the pre-divergence history of the founding population \u2014 the period before the people who would become the first Americans separated from their Asian relatives and began accumulating the distinct genetic character of Native Americans.<\/p>\n
These ancient genomes from the Asian side of the Bering region have helped researchers characterize the specific Asian populations that contributed to the founding of the Americas, refining the model of where the founding population came from and when it separated from its Asian relatives.<\/p>\n
The analysis of modern Native American genomes with increasing depth and breadth has also contributed to the refinement of the early American population models.<\/p>\n
<\/p>\n
Modern genomes contain the accumulated history of all the migrations, splits, and admixture events that have occurred since the founding period, and teasing apart these layers of history is a complex computational challenge.<\/p>\n
But as more modern Indigenous genomes are analyzed and as the computational methods improve, the signal of deep founding diversity \u2014 including signals that may reflect the Ancient Beringian contribution to modern populations \u2014 becomes more accessible.<\/p>\n
Some researchers have proposed, based on analysis of modern genomes, that the signal of Ancient Beringian ancestry may be detectable in certain modern populations \u2014 particularly in some Indigenous Alaskan communities, where the possibility of a geographic continuity between the Ancient Beringian region and later Athabascan communities has been suggested.<\/p>\n
These findings are preliminary and have not been universally accepted, but they raise the possibility that the Ancient Beringian lineage was not entirely replaced or absorbed but may have contributed a genetic component to some populations that persist to the present.<\/p>\n
<\/p>\n
The Pre-Clovis evidence and its implications for the founding models have also continued to develop.<\/p>\n
The White Sands dates, confirmed by multiple independent methods, establish that people were in the interior of North America during the Last Glacial Maximum \u2014 well before the earliest Clovis sites and well before the USR1 burial.<\/p>\n
This evidence forces the question of whether the White Sands people were related to the founding population that produced USR1 and the other well-documented early Americans, or whether they represent an earlier, separate founding event.<\/p>\n
No ancient genome from a pre-Clovis context has been successfully analyzed, so the genetic character of the White Sands people and their relationship to the USR1 lineage and to other ancient Americans remains unknown.<\/p>\n
<\/p>\n
This is one of the most significant gaps in the current understanding of early American genomic history, and filling it \u2014 if sites preserving ancient DNA from the relevant period can be identified \u2014 would substantially advance the field.<\/p>\n
Route And Timing \u2014 What Is Still Debated<\/p>\n
The specific route or routes by which the founding population of the Americas reached the hemisphere from northeastern Asia remains one of the most actively debated questions in the study of early Americans.<\/p>\n
The USR1 genome contributes to this debate but does not resolve it.<\/p>\n
Two main routes have been proposed and debated for decades.<\/p>\n
The first is the interior route \u2014 movement through the ice-free corridor that opened between the Laurentide and Cordilleran ice sheets as they retreated during the end of the Ice Age.<\/p>\n
<\/p>\n
The second is the coastal route \u2014 movement along the Pacific coast of Beringia and North America, following the productive kelp ecosystem that the coast supported.<\/p>\n
The ice-free corridor route is well-documented as a geographic reality.<\/p>\n
The corridor existed, it connected Alaska to the interior of the continent, and it was eventually traversed by people \u2014 the Clovis people and their successors clearly used the interior of the continent.<\/p>\n
The question is whether the corridor was available early enough, and whether it was ecologically productive enough, to support the passage of the founding population during the initial peopling of the Americas.<\/p>\n
The evidence increasingly suggests that the corridor was not available or productive enough during the very early period of human entry \u2014 roughly 20,000 to 14,000 years ago.<\/p>\n
<\/p>\n
Paleoecological reconstructions of the corridor indicate that it was a harsh, resource-poor environment during the period of maximum glaciation and the early phase of deglaciation.<\/p>\n
It may not have become a viable migration route until after 13,000 to 14,000 years ago \u2014 after the time when people were clearly present in South America and therefore after the initial southward expansion must have occurred.<\/p>\n
This chronological mismatch has strengthened the case for a coastal migration route as the primary pathway of the initial peopling.<\/p>\n
The Pacific coast of Beringia and North America offered a productive, resource-rich environment \u2014 the kelp ecosystem supported fish, shellfish, marine mammals, and seabirds \u2014 that could have sustained a mobile coastal people moving southward even during the period of maximum glaciation.<\/p>\n
The coast was also largely ice-free south of a certain latitude, unlike the interior, which was buried under ice.<\/p>\n
<\/p>\n
The USR1 genome does not directly address the route question, because it documents a population that was already in the interior of Alaska by 11,500 years ago \u2014 a date at which both the coastal route and the ice-free corridor were available, and which postdates the initial entry into the hemisphere regardless of the route taken.<\/p>\n
But the broader genomic evidence that the USR1 analysis fits within does contribute to the route debate.<\/p>\n
The Ancient Beringian lineage, if it reflects a population that remained in or near the Beringian region rather than following the main southward expansion, is consistent with a model in which the coastal migration moved south while a residual population \u2014 the Ancient Beringians \u2014 remained in the north.<\/p>\n
The geographic distribution of the Ancient Beringian lineage, as far as it can be characterized from a single genome, is consistent with a northern, interior Alaskan location rather than a coastal one.<\/p>\n
<\/p>\n
The specific route of the main southward expansion \u2014 the expansion that produced the ancestral population of most Native Americans \u2014 remains debated.<\/p>\n
The growing body of ancient DNA from early American sites will eventually provide more direct information about the routes taken, particularly if sites along the Pacific coast from the relevant period can be identified and sampled.<\/p>\n
The challenge is that coastal sites from the period of initial expansion are now largely underwater, submerged by the sea level rise that accompanied the melting of the glaciers.<\/p>\n
A Second Opening: The Genome Versus The People<\/p>\n
<\/p>\n
Around the point in any careful account of the USR1 findings where the scientific picture has been laid out \u2014 the basal position, the Ancient Beringian label, the demographic modeling, the questions about routes and timing \u2014 a different and in some ways more important question begins to demand attention.<\/p>\n
What does all of this mean for the people who are descended, in the relevant biological sense, from the founding population of the Americas?<\/p>\n
What does it mean for the Indigenous communities of Alaska, whose traditional territory includes the Upward Sun River site?<\/p>\n
What does it mean for the broader question of how we understand the history and the rights of Indigenous peoples in the Americas?<\/p>\n
The scientific findings from USR1 have specific and important implications for some of the political and legal debates about Indigenous history in the Americas.<\/p>\n
<\/p>\n
The finding that USR1 was most closely related to Native American populations \u2014 that the Ancient Beringians were not a separate, non-Native founding group but a distinct branch of the same Native American founding lineage \u2014 directly undercuts hypotheses that have been used to question the depth and exclusivity of Indigenous American presence.<\/p>\n
The two-migration or multiple-migration models that some researchers have proposed \u2014 models in which the first Americans were replaced by or supplemented by later, different populations \u2014 have sometimes been used in legal and political contexts to complicate Indigenous claims to the hemisphere.<\/p>\n
If the first Americans were not the ancestors of current Native peoples, the argument goes, then current Native peoples are not the original inhabitants in the relevant sense.<\/p>\n
The genetic evidence from USR1 and from the broader ancient American genomic record does not support this argument.<\/p>\n
<\/p>\n
The founding population of the Americas was the ancestor of all sampled Native American populations, including the Ancient Beringians.<\/p>\n
There is no genetic evidence of a separate, non-Native founding group that preceded the Native American founders.<\/p>\n
But the implications of the findings go deeper than the refutation of specific hypotheses.<\/p>\n
They speak to the question of what it means to know where you come from \u2014 and of the relationship between scientific knowledge and Indigenous knowledge about that question.<\/p>\n
The Athabascan communities with traditional territory at Upward Sun River know where they come from.<\/p>\n
They know it through their oral traditions, through their ceremonial practices, through their ecological knowledge of the landscape they have inhabited for as long as memory reaches, and through the specific cultural forms \u2014 language, kinship systems, spiritual practices \u2014 that connect them to their ancestors.<\/p>\n
<\/p>\n
That knowledge does not depend on genome sequencing, and it was not validated or invalidated by the USR1 findings.<\/p>\n
What the USR1 findings provided, for those communities, was not new knowledge about their origins but a scientific finding that was consistent with what they already knew: that their people are deeply and continuously connected to the landscape of Alaska, that their presence there is ancient, and that the specific genetic character of the founding population of the Americas was already in this region more than eleven thousand years ago.<\/p>\n
The consistency between the scientific finding and the Indigenous understanding is meaningful \u2014 not because Indigenous knowledge needed scientific validation, but because the two independent systems of knowing, working with very different methods and very different materials, arrived at a convergent conclusion about the antiquity and the continuity of human presence in this region.<\/p>\n
That convergence is something worth noting carefully, because it speaks to the specific question of what science can contribute to Indigenous history without displacing or replacing Indigenous ways of knowing that history.<\/p>\n
<\/p>\n
The Specific Value Of One Infant’s Genome<\/p>\n
It is worth being precise about what the USR1 genome can legitimately tell us and what it cannot, because the temptation \u2014 in scientific reporting and in popular accounts \u2014 is to claim too much for any single finding.<\/p>\n
What the USR1 genome tells us: that an infant who lived in interior Alaska approximately 11,500 years ago belonged to a genetic lineage that was basal to all other sampled Native American populations.<\/p>\n
That this lineage diverged from the ancestors of other Native Americans approximately 20,000 years ago, consistent with the Beringian standstill period.<\/p>\n
<\/p>\n
That the founding population of the Americas included at least two distinct branches \u2014 the Ancient Beringian lineage and the ancestors of other sampled Native Americans \u2014 before the main southward expansion began.<\/p>\n
That the Ancient Beringian lineage was genetically part of the Native American founding stock, not a separate non-Native population.<\/p>\n
What the USR1 genome does not tell us: the specific route by which the founding population reached the Americas.<\/p>\n
The exact timing of the initial entry into the hemisphere.<\/p>\n
Whether there were one or multiple distinct founding migrations from different Asian source populations.<\/p>\n
The cultural practices, language, social organization, or beliefs of the people USR1 belonged to.<\/p>\n
<\/p>\n
The specific fate of the Ancient Beringian lineage in the thousands of years after USR1.<\/p>\n
The genetic profiles of any other individuals in USR1’s community.<\/p>\n
One genome is a powerful data point.<\/p>\n
It is also one genome \u2014 one individual, representing one moment in a long and complex population history, sequenced to a depth that allows population genetic inference but not genealogical detail.<\/p>\n
The conclusions that can be drawn from it are probabilistic and population-level, not deterministic and individual.<\/p>\n
The appropriate response to the USR1 findings is neither to dismiss their importance \u2014 they are genuinely significant \u2014 nor to overclaim their reach.<\/p>\n
<\/p>\n
They tell us something specific and important about the early diversification of Native American populations.<\/p>\n
They do not tell us everything about that diversification, and the subsequent research that has built on and complicated the 2018 findings demonstrates that the story is more complex than the first publication could have revealed.<\/p>\n
The Weight Of A Tiny Skeleton<\/p>\n
All of the genetics and all of the demographics and all of the population tree diagrams and all of the routes and dates and model comparisons eventually return to a specific physical reality: a very small skeleton, found in a prehistoric hearth in Alaska, belonging to an infant who had lived approximately six weeks to three months and who had been buried with the care that the people who loved her could provide.<\/p>\n
USR1 was a person.<\/p>\n
<\/p>\n
She was the youngest person imaginable \u2014 a newborn, essentially, in her early weeks of life.<\/p>\n
She had not yet developed the social and cognitive complexity that we associate with older children and adults.<\/p>\n
She was not yet capable of many of the behaviors that would have defined her place in her community.<\/p>\n
She had not yet learned to walk or talk or understand the landscape she had been born into.<\/p>\n
And yet she was buried.<\/p>\n
The community she had been born into recognized her as a member of that community \u2014 as someone whose death required acknowledgment, whose passage from life to whatever they understood lay beyond required ceremony and care.<\/p>\n
<\/p>\n
The hearth in which she was placed had been the center of warmth and cooking and community life.<\/p>\n
Its repurposing as a burial space for the infant speaks to an understanding of the relationship between life and death \u2014 or between this world and the next \u2014 that connected the two in the specific geography of the hearth.<\/p>\n
What was thought, what was said, what was done, in the hours or days after her death \u2014 we cannot know.<\/p>\n
The record does not preserve words or gestures or grief.<\/p>\n
It preserves only the bones, carefully placed, and the ochre or other materials that accompanied her burial if any were used, and the stratigraphic evidence that tells us she was placed deliberately rather than randomly deposited.<\/p>\n
<\/p>\n
But the act of burial is itself a statement.<\/p>\n
It is the oldest and most universal human statement about the value of the individual \u2014 the assertion that this person mattered, that their passage from life required marking, that the community would not simply leave the dead where they fell but would invest time and care in giving them a proper place.<\/p>\n
USR1 was given that place.<\/p>\n
In a hearth, in the ground, in interior Alaska, eleven and a half thousand years ago.<\/p>\n
And the bones that were placed there with care by people who loved her have, in our time, become one of the most informative pieces of evidence we have about the founding of the human population of the Americas.<\/p>\n
<\/p>\n
The genome hidden in those tiny bones \u2014 degraded, fragmented, chemically damaged by eleven and a half millennia of burial \u2014 was still legible enough to reveal something that no amount of stone tool analysis or radiocarbon dating or isotopic study could have shown: that the first Americans were more diverse, their history more complex, their differentiation from each other more ancient, than the models of the twentieth century had imagined.<\/p>\n
She was basal to all of them.<\/p>\n
Not the ancestor of all of them \u2014 that is not what basal means.<\/p>\n
But the representative of a lineage that was there at the beginning, that split off before the main diversification began, that maintained its distinct genetic character for some ten thousand years after the split before she was born and before her tiny bones were placed in the hearth that held them for another eleven thousand years.<\/p>\n
A lost branch of the first Americans.<\/p>\n
<\/p>\n
Found in a baby.<\/p>\n
In Alaska.<\/p>\n
The story of who was first in the Americas has always been more complicated than any single model could contain.<\/p>\n
USR1 made it a little more complicated, and in doing so, a little more truthful.<\/p>\n
The Consultation That Shaped The Research<\/p>\n
The research at Upward Sun River was shaped, from its earliest phases, by consultation with Indigenous communities \u2014 a process that is worth describing in more detail than it typically receives in accounts of the scientific findings.<\/p>\n
Ben Potter and his team understood, from the beginning of their work at the site, that the Tanana Valley was the traditional territory of Athabascan communities who had both a legal interest in the treatment of ancient remains found within that territory and a cultural and historical interest in how those remains were interpreted and discussed.<\/p>\n
<\/p>\n
The Native Village of Tanana, the Healy Lake Village Council, and other Athabascan communities were engaged in conversations about the research as it developed.<\/p>\n
These conversations were not always simple.<\/p>\n
The communities involved have their own understandings of their history and their relationships to the landscape of the Tanana Valley \u2014 understandings that do not always map directly onto the categories and methods of population genetics.<\/p>\n
Questions about what the ancient remains could tell them, about who the infants were in terms of their community’s historical understanding, and about how the scientific findings should be communicated publicly, were discussed as part of an ongoing relationship between the researchers and the communities.<\/p>\n
The specific decision to pursue genetic analysis of the USR1 remains \u2014 a decision that required extracting material from the bones of an infant \u2014 was made within this consultation framework.<\/p>\n
<\/p>\n
The communities involved were informed about what the analysis would involve, what it might reveal, and what would be done with the remains after the analysis was complete.<\/p>\n
The findings from the USR1 analysis have been received with a range of responses by Athabascan communities and by the broader community of Indigenous scholars working in North America.<\/p>\n
Some have expressed the view that the findings \u2014 particularly the confirmation that the Ancient Beringians were genetically Native American, not a separate non-Native group \u2014 support Indigenous claims to ancient and continuous presence in the region.<\/p>\n
Others have raised questions about the appropriateness of genetic research on ancient remains, about the control of genetic data derived from Indigenous ancestors, and about the ways in which scientific categories like Ancient Beringian risk flattening and misrepresenting the complexity of Indigenous history.<\/p>\n
<\/p>\n
These responses are not mutually exclusive, and they are not all resolvable by additional scientific research.<\/p>\n
They reflect the genuine complexity of the relationship between Western science and Indigenous communities \u2014 a relationship shaped by a long history of research conducted without meaningful consent, findings used to serve non-Indigenous interests, and the systematic displacement of Indigenous knowledge by scientific authority.<\/p>\n
The Upward Sun River project has been, by most accounts, a more conscientious engagement with these questions than much previous ancient DNA research in North America.<\/p>\n
Whether it was sufficient \u2014 whether the consultation was genuinely meaningful, whether the communities affected had the power to shape the research in ways that mattered, whether the findings have been used and communicated in ways that serve Indigenous interests \u2014 is a question that the communities involved are best positioned to answer, and their answers are worth listening to.<\/p>\n
<\/p>\n
What The Landscape Remembers<\/p>\n
The Upward Sun River site is a specific place in the Tanana Valley of interior Alaska.<\/p>\n
The valley is wide and flat, bounded by mountain ranges that are visible on clear days from distances that make the mountains seem close even when they are not.<\/p>\n
The river \u2014 a tributary of the Tanana \u2014 runs through the valley, cutting through the glacial sediments that have accumulated since the Ice Age.<\/p>\n
The vegetation is the characteristic subarctic mix of black spruce, white spruce, birch, and willow, with wetlands in the lowlands and more open tundra on the higher ground.<\/p>\n
<\/p>\n
The landscape has changed since USR1 lived here.<\/p>\n
The specific configuration of spruce and birch in the valley \u2014 the tree line, the wetland margins, the river channels \u2014 is different from what it was 11,500 years ago, when the early Holocene warming was still transforming the late Pleistocene vegetation into the modern subarctic forest.<\/p>\n
The river itself has shifted in its channel multiple times since then, as rivers do.<\/p>\n
The animals that used the valley have changed \u2014 the woolly mammoths and horses of the late Pleistocene were gone by the early Holocene, replaced by the moose and caribou and bears and salmon that define the modern Alaskan interior ecosystem.<\/p>\n
<\/p>\n
But the mountains are still there.<\/p>\n
The valley is still there.<\/p>\n
The river is still there, feeding into the Tanana that feeds into the Yukon that finds its way to the Bering Sea.<\/p>\n
The Athabascan communities that have traditional territory throughout this landscape are still there \u2014 navigating the specific challenges of life in the subarctic in the twenty-first century, maintaining connections to the land and the river and the fish runs that have sustained human life in this region for as long as anyone can document.<\/p>\n
The infant buried in the hearth at Upward Sun River was part of a community that used this landscape in ways that were probably not entirely unlike the ways that Athabascan communities have used it in more recent times \u2014 following the salmon runs, hunting the mammals of the forest and the open country, moving through a familiar landscape with knowledge built up over generations of careful attention.<\/p>\n
<\/p>\n
The specific cultural forms of that ancient community are not recoverable.<\/p>\n
The specific language they spoke, the specific ceremonies they conducted, the specific social organization that structured their lives \u2014 all of this is gone.<\/p>\n
But the landscape itself persists.<\/p>\n
The salmon still run.<\/p>\n
The spruce still grow.<\/p>\n
The mountains are still visible on clear days.<\/p>\n
And in the ground \u2014 eleven and a half feet down, or wherever the specific stratigraphy placed her \u2014 the bones of a six-week-old infant were preserved long enough to tell a story about the founding of the human population of two continents.<\/p>\n
The landscape holds more than the bones.<\/p>\n
<\/p>\n
It holds the ongoing life of the communities that have been here since before the record that science can read \u2014 communities whose presence in this valley is older than 11,500 years, older than USR1 herself, extending back to the founding of the hemisphere’s human population and forward into a present that is still being made.<\/p>\n
Why Simplified Retellings Miss The Point<\/p>\n
There is a version of the Upward Sun River story \u2014 a simplified version \u2014 that says something like: scientists found a 12,000-year-old baby in Alaska, sequenced her DNA, and discovered a lost lineage of ancient people who were different from Native Americans.<\/p>\n
This version is wrong in its most important detail, and the detail matters.<\/p>\n
The Ancient Beringian lineage was not different from Native Americans.<\/p>\n
<\/p>\n
It was a branch of the Native American founding population \u2014 a distinct branch, one that diverged early and maintained its distinctiveness for thousands of years, but a branch of the same founding lineage that gave rise to all Native American peoples.<\/p>\n
USR1 was more closely related to Native Americans than to any non-American population.<\/p>\n
The Ancient Beringians were Native Americans in the deepest genetic sense \u2014 they were part of the founding population of the hemisphere.<\/p>\n
The simplified version that treats the Ancient Beringians as a separate, non-Native founding group \u2014 as a lost or vanished race that preceded the “real” Native Americans \u2014 is not only factually wrong but potentially harmful.<\/p>\n
It feeds a narrative that has been used repeatedly to question Indigenous claims to ancient presence in the Americas: the idea that there was a more ancient, mysterious people who were later replaced or displaced by the ancestors of contemporary Indigenous communities.<\/p>\n
<\/p>\n
This narrative has been applied to various early American sites and various anomalous-seeming early American skull morphologies, and it has been used to suggest that current Native peoples are not the original inhabitants of the hemisphere in the relevant sense.<\/p>\n
The USR1 genome does not support this narrative.<\/p>\n
It refutes it.<\/p>\n
The Ancient Beringians were part of the founding population of the Americas.<\/p>\n
The founding population of the Americas is the ancestor of all sampled Native American populations.<\/p>\n
The diversity within that founding population \u2014 the branching structure, the early divergences \u2014 reflects the natural processes of population differentiation that occur in any large, geographically spread population over thousands of years.<\/p>\n
It does not reflect the replacement of one people by another.<\/p>\n
<\/p>\n
The more accurate version of the story is also more interesting than the simplified version.<\/p>\n
It says: scientists found the genome of an 11,500-year-old infant in Alaska, and discovered that she belonged to a branch of the Native American founding lineage that had diverged from the ancestors of other Native Americans approximately 20,000 years ago \u2014 before the southward expansion that would eventually populate most of the hemisphere.<\/p>\n
This branch \u2014 the Ancient Beringians \u2014 had maintained its distinct genetic character for thousands of years and eventually became absorbed into or replaced by the populations that expanded into the region from the south.<\/p>\n
And this finding revealed that the founding of the Americas was more complex, the early diversity of the founding population more substantial, and the ancient history of Native Americans richer and more intricate than the models of the twentieth century had imagined.<\/p>\n
<\/p>\n
That is a true story.<\/p>\n
It is also a more respectful story \u2014 one that honors both the science and the people whose history the science is illuminating.<\/p>\n
The Infant As Data Point And As Person<\/p>\n
The scientific literature on USR1 refers to her as a genome, a specimen, an ancient individual.<\/p>\n
These are the appropriate terms for scientific discussion, and they reflect the legitimate needs of science to abstract from the specific to the general, to treat individuals as data points in the larger patterns that science is trying to identify.<\/p>\n
But USR1 was also a person.<\/p>\n
<\/p>\n
She was an infant who had been alive for perhaps six weeks \u2014 long enough to have been nursed, held, noticed, named.<\/p>\n
Long enough for the people around her to have begun the process of understanding who she was, what her personality might become, what role she would eventually play in the community into which she had been born.<\/p>\n
Long enough for them to love her, and to mourn her when she died.<\/p>\n
We do not know why she died.<\/p>\n
The skeletal evidence does not preserve the cause of death \u2014 infant mortality in pre-modern populations was high, and the causes were various.<\/p>\n
She may have died of illness.<\/p>\n
<\/p>\n
She may have died of exposure.<\/p>\n
She may have died of causes that left no trace in bone.<\/p>\n
We know only that she died, very young, and that the people who had been with her through her brief life buried her with care in a place that had been part of their daily existence.<\/p>\n
The hearth in which she was placed had been used for warmth and for cooking \u2014 for the most fundamental forms of sustaining life.<\/p>\n
Its repurposing as her resting place connected her departure from life to the center of life that the hearth represented.<\/p>\n
<\/p>\n
Whatever the specific meaning of that choice \u2014 and we cannot recover the specific meaning \u2014 it was a choice made by people who thought carefully about what her burial should be.<\/p>\n
Eleven and a half thousand years later, the care that those people invested in her burial was repaid in a way they could not have imagined: the bones they placed in the ground with love preserved enough biological material for scientists of the distant future to read the genetic story of the founding of the Americas.<\/p>\n
The people who buried her did not know they were doing this.<\/p>\n
They were doing something much simpler and much more human: they were honoring one of their own.<\/p>\n
<\/p>\n
They were saying, in the material language of burial, that this infant mattered.<\/p>\n
That her brief presence in their community had been real.<\/p>\n
That her departure from it required acknowledgment.<\/p>\n
Science has added a layer to that acknowledgment that spans eleven and a half millennia.<\/p>\n
The acknowledgment of the people who buried her spans the same distance, in a different but equally real form.<\/p>\n
Both forms of recognition \u2014 the scientific and the human \u2014 are valid.<\/p>\n
Neither replaces the other.<\/p>\n
<\/p>\n
The Most Important Genome In Alaskan Prehistory<\/p>\n
In the years since the 2018 paper, the USR1 genome has been reanalyzed, incorporated into larger comparative studies, and used as a reference point for understanding the early diversification of Native American populations.<\/p>\n
Its position in the growing database of ancient American genomes is secure: it remains, as of current research, the oldest genome recovered from Alaska and one of the most informative ancient American genomes ever analyzed.<\/p>\n
Its specific importance derives from several characteristics that work together to make it uniquely informative.<\/p>\n
<\/p>\n
First, the age: approximately 11,500 years before the present places USR1 in the critical period when the founding population of the Americas was still in the early stages of its geographic expansion and genetic diversification.<\/p>\n
Genomes from this period capture the founding diversity before it was diluted by subsequent migration, admixture, and population processes.<\/p>\n
Second, the location: interior Alaska is closer to the Beringian source region than almost any other location in North America, making it the most likely place to find representatives of the earliest and most deeply rooted branches of the Native American founding population.<\/p>\n
Third, the genetic position: the basal relationship of USR1’s lineage to all other sampled Native American populations means that she provides information about the founding population at its deepest sampled level.<\/p>\n
<\/p>\n
Genomes from populations that diverged later \u2014 after the main diversification events \u2014 carry the signal of those later divergences on top of the founding diversity.<\/p>\n
USR1 carries the founding diversity with less of the subsequent layering.<\/p>\n
The combination of these three characteristics \u2014 age, location, and genetic position \u2014 makes USR1 uniquely informative about the founding of the Americas and about the early history of the continent’s first human populations.<\/p>\n
Future research will add more ancient Alaskan and subarctic genomes, filling in the picture of how the ancient population of this region changed over time \u2014 how the Ancient Beringian lineage was gradually absorbed or replaced, when the populations ancestral to modern Athabascan communities arrived in the region, and how the specific genetic diversity of modern Indigenous Alaskans relates to the ancient diversity that USR1 represents.<\/p>\n
Those future findings will not diminish the importance of USR1.<\/p>\n
<\/p>\n
They will build on it.<\/p>\n
The infant from Upward Sun River has already told us something that no other data source \u2014 not the archaeology, not the isotopes, not the stone tools, not any other ancient genome \u2014 had been able to show: that the founding population of the Americas included a branch with a distinct and ancient character, rooted in Beringia, that diverged from the ancestors of other Native Americans before the great southward expansion began.<\/p>\n
That is a discovery that genuinely reshapes the story of the first Americans.<\/p>\n
Not because it introduces a separate, non-Native population \u2014 it does not.<\/p>\n
<\/p>\n
But because it reveals that the founding population of the Americas was more diverse, its internal structure more complex, its early history richer and more differentiated, than the models of the twentieth century allowed.<\/p>\n
The first Americans were not a monolith.<\/p>\n
They were a diverse founding population, carrying within themselves the seeds of the biological diversity that would eventually produce the hundreds of distinct Native nations of the hemisphere.<\/p>\n
USR1 \u2014 the Ancient Beringian infant from Upward Sun River \u2014 is the oldest and deepest window into that founding diversity that we have been able to read.<\/p>\n
She was Native American.<\/p>\n
<\/p>\n
She was basal.<\/p>\n
She was part of a lineage that diverged before the others.<\/p>\n
She was part of the founding.<\/p>\n
And she was a baby, buried in a hearth, in Alaska, eleven and a half thousand years ago, by people who loved her.<\/p>\n
Both things are true.<\/p>\n
Both things matter.<\/p>\n
The genome revealed the science.<\/p>\n
The burial revealed the humanity.<\/p>\n
<\/p>\n
Together, they tell the most important story in American prehistory: that the first Americans were here, they were diverse, they were human, and the people who came after them \u2014 all the people, all the nations, all the hundreds of distinct communities of the Americas \u2014 are their descendants and their inheritors.<\/p>\n
The story of who was first is also the story of who is here now.<\/p>\n
And that story is still being written, one genome at a time.<\/p>\n
The Deep Structure Of The Founding Population<\/p>\n
When researchers describe the founding population of the Americas, they are using language that can mislead if not unpacked carefully.<\/p>\n
The phrase implies a single, discrete group \u2014 a band of people who crossed from Asia at a specific moment and who can be identified as the source of all subsequent Native American populations.<\/p>\n
The reality that the genomic evidence reveals is considerably more complex.<\/p>\n
<\/p>\n
The founding population of the Americas was not a single band at a single moment.<\/p>\n
It was a set of people \u2014 probably numbering in the thousands, possibly more \u2014 who had been living in Beringia and adjacent parts of northeastern Asia for an extended period, accumulating the specific genetic character that distinguishes Native Americans from their Asian relatives, and gradually differentiating into subgroups through the ordinary processes of population structure that operate in any large, geographically distributed population.<\/p>\n
Within the founding population, some groups were in regular contact with others and therefore maintained gene flow \u2014 the exchange of genetic material through interbreeding that keeps populations genetically connected.<\/p>\n
Other groups became more isolated, either through geographic barriers or through the specific patterns of movement across the broad Beringian landscape, and began to accumulate distinct genetic signatures through the process of genetic drift.<\/p>\n
<\/p>\n
The Ancient Beringian lineage \u2014 the one represented by USR1 \u2014 was apparently one of these groups that became isolated early, before the main southward expansion began.<\/p>\n
The specific geographic and demographic circumstances that led to this isolation are not recoverable from the single genome of USR1.<\/p>\n
Was it a matter of the Ancient Beringians occupying a specific ecological niche or geographic territory that kept them separate from the proto-First American population?<\/p>\n
Was it a matter of the two groups being simply far enough apart that regular interbreeding was limited?<\/p>\n
Was it a matter of the specific movement patterns of different groups across the Beringian landscape?<\/p>\n
<\/p>\n
These questions are not answerable from the current data.<\/p>\n
What is answerable \u2014 at a rough level \u2014 is the approximate time of the divergence (around 20,000 years ago) and the approximate genetic distance between the two branches at the time of divergence.<\/p>\n
These parameters constrain the demographic models that researchers use to understand the founding of the Americas, and they contribute to the growing picture of a founding process that was more extended in time and more complex in its population structure than simple models suggest.<\/p>\n
The demographic modeling associated with the 2018 paper estimated the effective population size of the founding population \u2014 the number of individuals contributing to the genetic diversity of the population \u2014 in a range consistent with a relatively small but not tiny group.<\/p>\n
<\/p>\n
Estimates of this kind are highly uncertain, but they suggest a founding population of perhaps a few thousand individuals, distributed across the broad landscape of Beringia during the standstill period.<\/p>\n
A few thousand people distributed across a landscape the size of a large country, over a period of several thousand years, is not a single group in any sociological sense.<\/p>\n
It is many groups, in regular or occasional contact with each other, differentiated into local bands with their own knowledge of specific territories and their own cultural adaptations to specific ecological conditions.<\/p>\n
The genetic differentiation that produced the distinction between the Ancient Beringian lineage and the proto-First American lineage probably reflected a specific geographic and demographic configuration within this broader population \u2014 a configuration that the current evidence can describe only in the roughest outlines.<\/p>\n
<\/p>\n
The Salmon That Connects Past And Present<\/p>\n
There is a detail from the Upward Sun River site that is easy to overlook in the excitement about genomes and founding populations and demographic models, but that connects the ancient people of the site to the living communities of the Tanana Valley in an immediate and specific way.<\/p>\n
Salmon bones were found in the archaeological horizons at Upward Sun River.<\/p>\n
The people who camped at this site, 11,500 years ago, were fishing for salmon in the Tanana River system.<\/p>\n
<\/p>\n
Salmon are not native to the Tanana in the way that resident species like grayling are.<\/p>\n
They are anadromous \u2014 they spawn in the river, migrate to the ocean, and return to the river to spawn again after years at sea.<\/p>\n
The salmon runs are seasonal, predictable in their timing and location, and enormously productive when they occur.<\/p>\n
A community that knows when and where the salmon will arrive, and that has the means to harvest and process them in large quantities, can store enough protein to survive the winter months when other resources are scarce.<\/p>\n
This pattern \u2014 the exploitation of salmon runs as a core component of the annual subsistence cycle \u2014 is one of the most characteristic features of northern and northwestern North American Indigenous economies.<\/p>\n
<\/p>\n
It is a pattern that has defined the subsistence strategies of Athabascan communities in the Tanana Valley for as long as those communities have been in the region.<\/p>\n
And the salmon bones at Upward Sun River document that this pattern extends back at least 11,500 years \u2014 to the very beginning of the well-documented human occupation of the site.<\/p>\n
The implications are significant on several levels.<\/p>\n
They demonstrate that the people of the ancient site were not simply passing through, not explorers in the sense of people encountering an unfamiliar landscape for the first time.<\/p>\n
They were people who knew this landscape \u2014 who knew when the salmon would arrive, where the best fishing spots were, how to process and preserve the catch.<\/p>\n
<\/p>\n
This knowledge is the product of extended familiarity with a specific ecosystem, built up over generations of careful observation and transmitted from one generation to the next.<\/p>\n
This kind of ecological knowledge is exactly what living Athabascan communities have been developing and transmitting for as long as their communities have been in the region.<\/p>\n
The specific knowledge of salmon behavior, river conditions, and fishing techniques that contemporary Athabascan families use when they go to their fish camps on the Tanana and its tributaries is the current form of a knowledge tradition that extends back at least 11,500 years.<\/p>\n
The genetics can document the biological continuity between ancient and modern populations \u2014 or the lack thereof.<\/p>\n
<\/p>\n
But the salmon bones document something different: the continuity of a specific relationship between people and a specific ecosystem, maintained across thousands of years and expressed in practices that are alive and functional in the contemporary world.<\/p>\n
This is the kind of continuity that genetic analysis cannot capture but that is equally real and equally important for understanding what the first Americans were and who their descendants are.<\/p>\n
The Kelp Highway And Its Consequences<\/p>\n
The coastal migration hypothesis \u2014 sometimes called the kelp highway hypothesis because of the productive kelp ecosystems that would have lined the deglaciated Pacific coast \u2014 has been gaining support from multiple lines of evidence over the past two decades.<\/p>\n
The USR1 discovery does not directly address the coastal route, but understanding how USR1 fits within the broader context of early American migration requires engaging with the coastal hypothesis and its implications.<\/p>\n
<\/p>\n
The kelp highway hypothesis proposes that the primary route of the initial peopling of the Americas was along the Pacific coast, not through the ice-free interior corridor.<\/p>\n
The productive marine ecosystems of the North Pacific coast \u2014 the kelp forests that support dense populations of fish, shellfish, marine mammals, and seabirds \u2014 would have provided a rich and reliable food source for people moving southward along the coast.<\/p>\n
The coast was largely ice-free south of a certain latitude even during the Last Glacial Maximum, unlike the interior of the continent, which was covered by glaciers.<\/p>\n
And the coast offered a relatively direct path from the Beringian source region to the southern tip of the Americas.<\/p>\n
<\/p>\n
The challenge with the coastal hypothesis is the same one that confronts any hypothesis about events that took place along coastlines during the Ice Age: the coast of 15,000 to 20,000 years ago is now underwater.<\/p>\n
Sea levels were 120 to 130 meters lower during the glacial maximum than they are today, and the rise in sea level as the glaciers melted \u2014 a process that unfolded over several thousand years \u2014 submerged the coastal landscapes where the earliest coastal Americans would have camped, fished, and died.<\/p>\n
Sites that would directly document a coastal migration route are therefore largely inaccessible to standard archaeological survey.<\/p>\n
Some have been found by underwater archaeologists working along the submerged continental shelf, and the evidence from these sites is consistent with early coastal occupation \u2014 but the recovery is difficult and the evidence sparse.<\/p>\n
<\/p>\n
Where the coastal hypothesis connects to the USR1 story is through the model of how the Ancient Beringian and proto-First American lineages diverged.<\/p>\n
If the proto-First Americans moved south along the coast while the Ancient Beringians remained in the interior of the Beringian region, the geographic separation of the two groups would have facilitated the genetic divergence that produced the distinct lineages.<\/p>\n
The Ancient Beringians would have been the interior Beringian branch; the proto-First Americans would have been the coastal branch, moving south along a route that eventually connected Beringia to the rest of the Americas.<\/p>\n
This geographic model is speculative \u2014 it goes beyond what the USR1 genome alone can establish \u2014 but it is consistent with the genetic evidence and with the geographic distribution of the two lineages as far as it can be characterized.<\/p>\n
<\/p>\n
The Ancient Beringians were found in the interior of Alaska.<\/p>\n
The proto-First Americans’ southward expansion produced populations distributed across the entire hemisphere.<\/p>\n
A model in which the ancient Beringians occupied the interior while the proto-First Americans followed the coast to the south has a geographic logic that the genetics and the archaeology both support.<\/p>\n
If this model is correct, the USR1 infant is the representative of a lineage that stayed behind \u2014 the people who remained in the Beringian interior while others followed the coast southward and populated the rest of the hemisphere.<\/p>\n
That framing is evocative, but it should be held lightly: the specific behavioral and geographic patterns of the divergence are not established, only the genetic pattern of the divergence itself.<\/p>\n
<\/p>\n
The Competing Models That Remain<\/p>\n
The 2018 USR1 paper proposed a specific two-branch model for the founding of the Americas, with the Ancient Beringian branch diverging before the southward expansion of the main First American branch.<\/p>\n
This model has been incorporated into subsequent work, but it has also been questioned and refined.<\/p>\n
One significant complication comes from the evidence for pre-Clovis human presence in the Americas \u2014 specifically the White Sands footprints, dated to approximately 21,000 to 23,000 years ago.<\/p>\n
If people were in the interior of North America during the Last Glacial Maximum, they must have been there before the Ancient Beringian \/ First American divergence that the 2018 model places at approximately 20,000 years ago.<\/p>\n
<\/p>\n
Or the divergence date needs to be revised.<\/p>\n
Or the White Sands people represent a separate founding event that preceded the founding population represented by USR1 and other well-documented early Americans.<\/p>\n
This is one of the central unresolved tensions in the study of early Americans.<\/p>\n
The genetic models and the archaeological evidence are not yet fully consistent with each other, and the reason they are not consistent is not clear.<\/p>\n
It could be that the demographic models need to be revised with better data.<\/p>\n
<\/p>\n
It could be that the White Sands dates, while strongly supported, need additional independent confirmation.<\/p>\n
It could be that the relationship between the White Sands people and the founding population represented by USR1 is more complex than either a single founding event or a complete population replacement would suggest.<\/p>\n
Resolving this tension requires ancient DNA from pre-Clovis contexts \u2014 from sites old enough to represent the people who made the White Sands footprints or their close contemporaries.<\/p>\n
No such ancient DNA has been successfully analyzed, because sites from this period are rare, because the relevant sites have mostly been found in environments hostile to DNA preservation (exposed surface sites, underwater sites), and because the specific bones or teeth needed for ancient DNA analysis have not been recovered.<\/p>\n
<\/p>\n
The search for pre-Clovis ancient DNA is one of the most active frontiers in early American genomics.<\/p>\n
If ancient DNA from a pre-Clovis individual were recovered and analyzed, it would either confirm the founding population model \u2014 showing that the White Sands people were genetically related to USR1 and to other early Americans \u2014 or it would reveal a different ancestry, suggesting a more complex founding history than the current models allow.<\/p>\n
Until that data becomes available, the tension between the genetic models and the archaeological evidence remains an open question.<\/p>\n
The USR1 genome is an important piece of the puzzle, but it does not complete the puzzle.<\/p>\n
<\/p>\n
The picture of the founding of the Americas is still being assembled, one ancient genome at a time.<\/p>\n
Why Alaska Is The Key To Understanding Everything That Came After<\/p>\n
The importance of the Upward Sun River site \u2014 and of Alaska more broadly \u2014 for understanding the founding of the Americas cannot be overstated.<\/p>\n
Alaska is where the story begins, in a geographic sense, and the ancient genomic record of Alaska is the closest thing we have to a direct window into the founding population before it spread across the hemisphere.<\/p>\n
The founding population of the Americas entered from the northeast \u2014 from Beringia, across the land bridge that connected Asia to Alaska when sea levels were low.<\/p>\n
<\/p>\n
The first movement of people into the Americas, whatever its precise timing and route, involved people moving from the Beringian region into what is now Alaska.<\/p>\n
Alaska is therefore the geographic source region for the entire hemisphere’s Indigenous population \u2014 the place where the founding population was first present in the Americas in the sense that we understand that term.<\/p>\n
Finding an ancient individual in Alaska whose genome is basal to all other sampled Native American populations is exactly what we would predict if we had successfully sampled the founding population close to the source.<\/p>\n
USR1’s position in the family tree of Native Americans reflects her geographic location as well as her temporal one: she was in the right place, at the right time, to represent a branch of the founding population that had not yet been diluted by the demographic processes of the southward expansion.<\/p>\n
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This makes Alaska \u2014 and specifically the interior of Alaska, which is the most likely location for the residual Ancient Beringian population after the main southward expansion \u2014 the most important region in North America for future ancient DNA research on early American populations.<\/p>\n
Additional ancient genomes from Alaskan sites of similar or greater age to USR1 would dramatically increase our understanding of the early structure of the founding population, the timing and geography of the Ancient Beringian \/ proto-First American divergence, and the fate of the Ancient Beringian lineage in the millennia following USR1.<\/p>\n
The archaeological record of Alaska is rich with sites from the relevant period \u2014 the late Pleistocene and early Holocene \u2014 many of which have been excavated or at least surveyed in sufficient detail to know that human remains might be present.<\/p>\n
The challenge is that ancient DNA preservation in Alaskan sites is variable, dependent on the specific burial conditions and the thermal history of the site since deposition.<\/p>\n
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Not every site will yield usable ancient DNA, even from the relevant period.<\/p>\n
But the identification and careful excavation of sites with good preservation potential \u2014 like Upward Sun River \u2014 will yield, over time, the additional genomes that will fill in the picture that USR1 opened up.<\/p>\n
The Living Relationship To The Dead<\/p>\n
In the Athabascan cultural tradition, as in many Indigenous traditions across North America and the world, the dead do not cease to be members of the community at the moment of their death.<\/p>\n
The relationship between the living and the dead is maintained through ceremony, through memory, through the specific cultural practices that acknowledge the ongoing presence of ancestors in the lives of their descendants.<\/p>\n
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This understanding of the dead as continuing to be in relationship with the living is relevant to the story of USR1 in ways that the scientific literature does not always acknowledge.<\/p>\n
When the Tanana Athabascan communities with traditional territory at Upward Sun River engaged in consultation about the research at the site, they were not simply navigating a regulatory process or providing input on a scientific project that was fundamentally separate from their own understanding of the world.<\/p>\n
They were engaging with questions about the treatment of a person \u2014 an infant who had been part of a community, who had been buried with care, and who had been resting in the earth for eleven and a half thousand years \u2014 from within a cultural framework in which that person’s status as a community member did not automatically expire.<\/p>\n
The scientific finding that USR1 represented a distinct ancient lineage \u2014 one that may or may not have direct biological continuity with modern Athabascan communities \u2014 does not change this relationship in the way that some outside observers might assume.<\/p>\n
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The concept of cultural affiliation \u2014 the legal standard used under NAGPRA to determine which modern communities have a claim on ancient remains \u2014 is a Western legal concept that does not capture the full range of ways in which Indigenous communities understand their relationships to ancient people found in their traditional territories.<\/p>\n
For many Athabascan people, the question of whether USR1 was a biological ancestor of their specific community is less important than the question of whether she was a person found in their land \u2014 a person who deserves to be treated with respect regardless of whether she can be biologically linked to any specific modern family line.<\/p>\n
The land itself creates a form of relationship.<\/p>\n
The responsibility to care for those found in your territory extends to those who have been there for twelve thousand years as surely as to those who have been there for two generations.<\/p>\n
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This understanding of territorial and ancestral responsibility is something that the scientific research at Upward Sun River has engaged with, at least in part.<\/p>\n