What the Paisley result did was add another line of evidence from a different geographic region, with a different type of evidence — ancient DNA in directly dated biological material — pointing toward the same conclusion that Monte Verde and other sites had been suggesting: the Americas were inhabited before Clovis.

But the specific nature of the Paisley evidence — ancient DNA analysis, a technique with specific vulnerabilities to contamination and misinterpretation — made the result particularly easy to attack on methodological grounds.

And the critics who attacked it were not wrong to do so.

The First Wave of Doubt

The published criticism of the 2008 Paisley paper appeared in Science in 2009, from two groups of researchers who raised specific, technical objections that could not be dismissed.

Hendrik Poinar and colleagues identified several concerns about the evidence’s reliability.