Revealing a massive amount of earlier unexplained genetic variation, the paper offers new clues into our evolutionary past and emphasizes the difficulty of the process through which our ancestors varied, migrated, and combined all over the globe.
Important ‘Mixing Events’ Among Known Lineages
The study has been published in the prestigious journal Science and was led by researchers from the University of Cambridge, the Wellcome Sanger Institute, and other partners. It is the first research to date to use the latest high-quality sequencing technology to such a wide and varied set of humans, including 929 genomes from 54 geographically, linguistically, and culturally different populations across the world.
Scientists analyzed the sequencing data to examine evidence of mixing between the ancestors of modern humans and extinct human clans such as the Neanderthals and Denisovans, which appeared between 40,000 to 60,000 years ago.
They found proof that the Neanderthal lineage of modern humans can be detailed by only one significant interbreeding event, most probably including a few Neanderthal individuals contacting modern humans immediately after the latter had spread out of Africa.
“Studying the patterns of Neanderthal ancestry in present-day humans hints at the structure of human communities more than 50,000 years ago. It is remarkable that patterns of Neanderthal ancestry are so similar in populations around the world today and may have derived from a single Neanderthal population,” said Dr. Aylwyn Scally, a scientist at the University of Cambridge’s Department of Genetics who was involved in the research.
Most of the Variations Are From All Over the World
By comparison, several various sets of DNA segments native to Denisovans were found in people from Oceania and East Asia, implying at least two different ‘mixing events.’
“This could suggest that multiple small groups of Denisovans once lived in different regions of Asia. We expect future discoveries of ancient DNA – perhaps from other extinct humans and perhaps even inside Africa – to tell us more about ancient population structure and diversity,” explained Dr. Ruoyun Hui at the University of Cambridge’s Department of Genetics, who was also in the research team.
The scientists discovered millions of earlier unknown DNA variations that are exclusive to one continental or significant geographical region. Although the majority of those are rare, they included regular variations in particular African and Oceanian populations that had not been considered in prior research. These variations may impact the tendency of different groups to disease.
Medical genetic papers have, until now, mainly been focused on populations of European ancestry, which means that any medical effects that these variants might have are currently unknown. Detecting these new variants is a step forward towards completely expanding the study of genomics to poorly represented populations.
Still, not one DNA variation was found to exist in 100 percent of genomes from any significant geographical region while being absent from all other areas. This discovery highlights the fact that most of the common genetic variation is found all over the globe.
“The detail provided by this study allows us to look deeper into human history, particularly inside Africa where less is currently known about the timescale of human evolution,” said Dr. Anders Bergstrom, of the Francis Crick Institute and formerly the Wellcome Sanger Institute.