New genomes, new discoveries
The new research has been submitted to a scientific journal for publication. Under the journal's rules, lead author Reich cannot speak to the news media about the study until the paper comes out.
A Nature News reporter who attended the Nov. 18 talk, however, reports that Reich and his colleagues have created much more complete sequences of the Denisovan and Neanderthal genomes than those used in previous research.
The sequences confirmed previous findings that Denisovans mated with the ancestors of Pacific Islanders and East Asians, but also revealed a surprise: Genetic traces of an unknown population of human ancestors were found in the Denisovan gene, suggesting even more interbreeding than previously expected. Mark Thomas, an evolutionary geneticist at University College London, described the ancient environment to Nature as a "'Lord of the Rings'-type world" with many human populations living side-by-side.
Lalueza-Fox said the question of the mystery fourth ancestor is a "paleontological debate," but that the genetic work done by Reich and his colleagues opens the door to a deeper understanding of the individual diversity of ancient human ancestors. New techniques will enable researchers to tease out original DNA from later contaminants, he said.
"Some samples that were considered not suitable for genomic approaches are now going to be good samples," Lalueza-Fox said.
In the past, Lalueza-Fox said, geneticists were stuck trying to extrapolate details about human evolution from modern human DNA. Now, he said, they can go directly to the ancient DNA.
"We have been trying to understand human evolution from the study of modern human genomes, but clearly we missed part of the picture, which is now emerging from ancient hominin genomes," Lalueza-Fox said.
Original article on LiveScience.
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