Yeah, I should have _thought_ to look there, right? Sort of a duh thing.
Here are the perpetrators:
Rohde DL, Olson S, Chang JT (September 2004). "Modelling the recent common ancestry of all living humans". Nature 431 (7008): 562–6. doi:10.1038/nature02842. PMID 15457259.
What did they do? They wrote a computer simulation. Never a good sign; computer simulations embed cultural assumptions and make them very, very not-transparent unless you have access to the code. "For conservative parameters, he pushes back the date for the MRCA to the 6th millennium BC (p. 20),". This, I would be prepared to contemplate. At least, I don't find it as obviously in-credible as I found the 50th cousin theory which is, on the face of it, ludicrous.
"but still concludes with a "surprisingly recent" estimate of a MRCA living in the second or first millennium BC (p. 27). An explanation of this result is that, while humanity's MRCA was indeed a Paleolithic individual up to early modern times, the European explorers of the 16th and 17th centuries would have fathered enough offspring so that some "mainland" ancestry by today pervades even remote habitats."
I'm not sure if that's really clear to a casual reader, so I'm going to run it through my standard de-jargonator: white colonizers didn't leave any community un-colonized. Anywhere. Again, on the face of it, patently absurd. There are still communities without white ancestry: North Sentinel Island and some groups in the Amazon spring to mind, but I'm sure with even a small amount of effort, we could come up with more. Assuming that the white men went everywhere and successfully left offspring everywhere -- even where they didn't -- is _exactly_ the kind of racism we work really hard to expose. Embedding it in a computer simulation and then getting it reproduced without any qualifiers all over the place is a fucking crime.
The wikipedia entry, amazingly, gets this mostly right.
"Other models reported in Rohde, Olson, and Chang (2004) suggest that the MRCA of Western Europeans and people of Western European ancestry lived as recently as AD 1000."
At least this one requires a little more thought before scoffing at openly. Give me time, tho, give me time.
ETA: Honest to goddess, this kind of thing should give geneticists making dumb assumptions pause:
IT IS NOT SCIENCE IF YOU JUST REPRODUCE PREJUDICE. Also, it makes us look bad.