Scientists Use Revolutionary Technological Advance to Locate Human DNA

The Telegraph (and other outlets) are reporting on an incredible breakthrough that allows the recovery of human DNA from sediment where no actual human fossil remains exist:

The researchers collected 85 sediment samples from seven caves in Europe and Russia that humans are known to have entered or even lived during the Pleistocene, between 14,000 and 550,000 years ago.

By refining a method previously used to find plant and animal DNA, they were able to search specifically for genetic material belonging to ancient humans and other mammals.

"This work represents an enormous scientific breakthrough," said Antonio Rosas, scientist at Spain's Natural Science Museum in Madrid.

"We can now tell which species of hominid occupied a cave and on which particular stratigraphic level, even when no bone or skeletal remains are present."

Scientists focused on mitochondrial DNA, which is passed down the maternal line, because it is particularly suited to telling apart closely related species. By analysing damaged molecules they were able to separate ancient genetic material from any contamination left behind by modern visitors.

It is difficult to overestimate the importance and impact this will have on the anthropological world. This technique will allow us to reconstruct migration routes, occupational histories, times of first appearance in an area and many other aspects of Neandertal, Denisovan and modern human demography.This will open doors to research that we can only begin to imagine.

Native American Migrations

USA Today reports on genetic research indicating three separate waves of migration out of Asia into the New World beginning around 15 ooo years ago. Dan Vergano writes:

North and South America were totally empty of people until the first arrivals from Siberia crossed a land bridge into Alaska, spreading in a few thousand years to the tip of South America. The genetic study may help settle a debate between a long-held view that the populating of the continents came as one event instead of the more recently supported notion, backed by this study in the journal Nature, that the migration happened in three distinct waves.

"Our study makes clear that mixing of these three ancient populations is the story of Native American arrival," says geneticist David Reich of Harvard Medical School, lead author of the study.

As far back as I can remember in graduate school, I was taught that there were at least two, probably three migrations. The two that I remember studying were from the Lena River Basin in Siberia and the Amur River basin, on the border of Russia and China. There were probably more than that, as there are some Native American populations that have gene fixation for certain blood types, a situation that would only occur in a drift/founder effect situation. I remember Dick Jantz teaching us this twenty years ago, at UT.

----------------
Now playing: Simon & Garfunkel - The Dangling Conversation
via FoxyTunes

Denisova Update

John Hawks does not think that the recent data from the paper by Skoglund and Jakobsson holds up under scrutiny. He cites striking discrepancies between the analysis presented by these two with a paper that came out by Reich et al. (http://dx.doi.org/10.1016/j.ajhg.2011.09.005) called “Denisova admixture and the first modern human dispersals into southeast Asia and oceania.” Their salient finding is that there were very few Denisovan markers in mainland Asian populations.

Hawks suggests that the reason the two papers differ so greatly is that in the paper by Skoglund and Jakobsson, the analysis is picking up only slight differences in gene frequencies between populations, and that, while there is hybridization and migration into the area by Denisovans, it is small in amount. He writes:

We aren't very far from a more definitive answer of this question, as the data continue to accumulate every day. What I find interesting is the way that models can generate these 1% differences in ancestry proportions, depending on sampling and the pattern of migration assumed to have happened in the past. Two estimates that differ by less than a percent are not really different. This paper provides the suggestion of a more widespread Denisovan legacy, and I accept that as a possibility.

It is clear that there was some interbreeding between these populations. How much remains to be seen.

Hat tip to Paul Pavao.
----------------
Now playing: Steve Hackett - Four Winds: West
via FoxyTunes