The human genome mainly overlaps with Neanderthals, other human ancestors

Humans like to think they’re special, but our genes suggest that’s far from being the case.

No more than 7% of the human genome is unique to Homo sapiens, according to a study published Friday in the journal Science Advances.

We share the remaining pieces of our genetic material with other human ancestors, or hominids, including our Neanderthal cousins ​​and the Denisovans first discovered in East Asia.

“The evolutionary family tree shows that there are regions of our genome that make us unique human beings,” Richard Green, director of the paleogenomics laboratory at the University of California at Santa Cruz, told Insider and co- author of the new study. “Now we have a catalog of it, and it’s a surprisingly small fraction of the genome.”

Anthropologists already knew that our hominin ancestors all interacted and crossed each other, exchanging genes and stone technologies that changed the course of our species’ evolution. But these new findings further underscore how frequently this mixing has occurred in the past 300,000 years or so, since the emergence of the first known population of modern humans.

“More or less everywhere we look, mixing is not at all the exception, but rather the rule,” Green said.

Genetic evidence suggests our ancestors crossed paths with mysterious hominids

To build a hominid family tree, Green’s team sequenced and compared the genomes of 279 modern humans – sampled from people around the world – to the ancient genomes of a Denisovan and two Neanderthals. Then the researchers used a computer algorithm to determine how each of these individuals relates to each other.

The scan tool, which Green said took years to develop, helped them distinguish which parts of the human genome are devoid of mixing, meaning those sets of genes aren’t visible in Neanderthals. or the Denisovans.

The algorithm also highlighted the genes that humans inherited from an even older ancestor, one who lived around 500,000 years ago, who ultimately gave birth to our species as well as Neanderthals and others. hominids.

The study results suggest that mysterious populations of human ancestors that scientists have yet to discover may have crossed paths with Neanderthals and Denisovans before these species mixed with modern humans, added. Green.

Genes unique to humans are linked to the development of our brains

Researchers have already identified many human genes resulting from interspecies rendezvous, but this is the first study to identify which regions of genes were completely devoid of mixing, according to Green.

His group found that these uniquely human regions of our genome were “incredibly enriched with genes linked to neural development,” Green said.

While Neanderthals have heads as big, if not bigger than humans, this skull size tells us little about how their brains work compared to ours.

“Now we know that things specific to humans have to do with brain function,” Green said.

And most of these unique human genes came out in two separate evolutionary spurts – one that happened 600,000 years ago and the other 200,000 years ago – according to the study.

One of those evolutionary waves could have laid the genetic foundation for human communication, Green said.

“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 control of speech and language,” he said. .