April 9, 2014
Genomic Analysis Confirms Interbreeding Between Humans And Neanderthals
April Flowers for redOrbit.com - Your Universe Online
Whether or not early humans and Neanderthals interbred has been the subject of much debate in scientific circles for a long time. Thanks to a new genomic analysis method from the University of Edinburgh, technical objections to that idea have been overcome.
The technique, described in a recent issue of GENETICS, is able to detect the genetic signatures of interbreeding with more confidence than previous methods. The research team believes their new technique will be useful for evolutionary studies of other ancient or rare DNA samples.
"Our approach can distinguish between two subtly different scenarios that could explain the genetic similarities shared by Neanderthals and modern humans from Europe and Asia," said Konrad Lohse, a population geneticist at the University of Edinburgh.
In scenario number one, the modern humans occasionally interbred with Neanderthals after the humans migrated out of Africa. The second scenario theorizes that the humans evolved from the same ancestral subpopulation in Africa as the Neanderthals.
The interbreeding scenario seems more likely to many scientists because it fits the genetic patterns seen in previous studies that compared genomes from modern humans, but nothing was definitive. The second scenario has finally been completely ruled out by the new technique — without requiring all the extra data — by using only the information from one genome each of several types: Neanderthal, European/Asian, African and chimpanzee.
The team plans to use their new technique in other studies of interbreeding where limited samples are available. "Because the method makes maximum use of the information contained in individual genomes, it is particularly exciting for revealing the history of species that are rare or extinct," said Lohse. In fact, the new technique was not developed for humans and Neanderthals, but rather during studies of the history of insect populations around Europe and island species of rare pigs in South East Asia.
Although the new method discounts the second theory, Lohse still cautions against reading too much into the results. Although it estimates a slightly higher genetic contribution of Neanderthals to modern humans than previous studies, Lohse said that estimating this contribution is complex and is likely to vary slightly between different approaches.
"This work is important because it closes a hole in the argument about whether Neanderthals interbred with humans. And the method can be applied to understanding the evolutionary history of other organisms, including endangered species," said Mark Johnston, Editor-in-Chief of the GENETICS.