A new genome analysis method has confirmed that Neanderthals interbred with ancestors of Eurasians, a new study reports.
The findings, published in the April 2014 issue of the journal Genetics, explains how Neanderthals most likely interbred with modern humans after they migrated out of Africa. The new technique ruled out the other popular theory that humans who left Africa evolved from the same ancestral subpopulation where Neanderthals evolved from.
"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," Konrad Lohse, study co-author and population geneticist at the University of Edinburgh in Scotland, said in a statement.
The method differs from others in that it used one genome from Neanderthals, Eurasians, Africans and chimpanzees rather than comparing genomes from many modern humans. The same method will have other uses to, especially in studies of suspected interbreeding where limited samples are available.
“We did a bunch of math to compute the likelihood of two different scenarios," Laurent Frantz, study co-author and evolutionary biologist at Wageningen University in the Netherlands, told The Verge. "We were able to do that by dividing the genome in small blocks of equal lengths from which we inferred genealogy."
Scientists developed the method after studying the history of insect populations in Europe and rare pig species in Southeast Asia.
"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," Mark Johnston, editor-in-chief of the journal Genetics, said.
Frantz thinks the study may also change the way evolution is perceived.
"There have been a lot of arguments about what happened to these species," he said. "Some think that we outcompeted [other hominins] or that they were killed by humans, but now we can see that it's not that simple."
Neanderthals may have been recruited into certain human populations that they may have been in contact with on a daily basis. This goes against a commonly held perception of evolution where species struggled to survive.
"Human evolution is much more complex than we previously thought," Frantz said.