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You may have heard of the fact that modern humans share a fairly large part of our genomes with bananas. But digging much deeper, how much of our genome is only Homo sapiens.
A new study has suggested that number could be as small as 1.5%, with the rest being shared with our former relatives such as Neanderthals and Denisovans.
“We are generating a map within human genomes of archaic ancestry and genomic regions not shared with archaic hominids,” the team wrote in their new paper.
“We find that only 1.5 to 7 percent of the modern human genome is uniquely human.”
Unraveling what belongs to us and what comes from our former parents is a difficult task. How to know which genetic variants are due to interbreeding (also called mixing) of Neanderthals and homo sapiens for example, rather than variants transmitted to both species by a common ancestor?
The team wanted to create a system that could identify both mixing events as well as this shared inheritance – called incomplete lineage sorting – that would help us tell us which regions of our genome are unique to us.
They created an algorithm called SARGE – Speedy Ancestral Recombination Graph Estimator – so they could map how our genes have woven together through time and species, separating and coming together at different points using what we call ancestral recombination graphics.
They performed SARGE on 279 modern human genomes from Africa and elsewhere, two high-quality Neanderthal genomes and one high-quality Denisovan genome.
“Using the resulting ancestral recombination plot, we map Neanderthal and Denisovan ancestry, incomplete lineage sorting, and the absence of both in modern human genomes,” the team wrote.
“We find evidence of at least one wave of Neanderthal mixing in the ancestors of all non-Africans.”
In addition to the 1.5 to 7 percent of the genome that is unique to modern man, they also found “evidence of multiple bursts of adaptive changes specific to modern man over the past 600,000 years involving genes. related to the development and function of the brain ”.
The researchers explain that most of these genes that were ours were not genes with unknown functions, but rather well-known genes that coded for proteins used in the brain.
Obviously, it’s not even near the end of the story. For starters, between 1.5 and 7% is a pretty wide range and the team thinks they can make it more specific with more genomes and more research.
There have also been many other analyzes on the percentage of DNA we take from our old cousins, so this is unlikely to be the last word on the matter.
Additionally, SARGE is unable to tell researchers why these bursts of adaptive change occurred at this time.
However, the team already has some ideas.
“It is extremely tempting to speculate that one or more of these bursts has something to do with the incredibly social behavior of humans – mediated in large part by our expert speech and language control,” University of California, paleogeneticist of Santa Cruz and one of the researchers, Richard Green, told Business Insider.
The research was published in Scientists progress.
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