Two comments on ancient mtDNA from Native American coprolites

They are referring to the paper by Thomas et al. which detected mtDNA haplogroups A2 and B2 in pre-Clovis Americans. The arguments are highly technical, so I won't express an opinion on who of the two is right.

My default position is to have a question-mark next to every ancient DNA study, whether it has been formally criticized or not. Only when a large number of such studies from a similar time/place and by different researchers produce similar results, will we be justified, I think, to remove that question mark.

Science 10 July 2009:
Vol. 325. no. 5937, p. 148
DOI: 10.1126/science.1168182

Comment on "DNA from Pre-Clovis Human Coprolites in Oregon, North America"

Hendrik Poinar et al.

Gilbert et al. (Reports, 9 May 2008, p. 786) analyzed DNA from radiocarbon-dated paleofecal remains from Paisley Cave, Oregon, which ostensibly demonstrate a human presence in North America predating the well-established Clovis complex. We question the authenticity of their DNA results and argue that in the absence of intact stratigraphy and diagnostic artifacts, and in view of carbon isotope anomalies, the radiocarbon dates of the oldest specimens are unreliable.

Link

Science 10 July 2009:
Vol. 325. no. 5937, p. 148
DOI: 10.1126/science.1168457

Response to Comment by Poinar et al. on "DNA from Pre-Clovis Human Coprolites in Oregon, North America"

M. Thomas et al.

The arguments of Poinar et al. neither challenge our conclusions nor would contribute to the verification of our data. We counter their questions about the authenticity of our ancient DNA results and the reliability of the radiocarbon data and stand by the conclusion that our data provide strong evidence of pre-Clovis Native Americans.

Link