These baboons borrowed a third of their genes from their cousins

New genetic analyzes of wild baboons in southern Kenya reveal that most of them carry traces of hybridization in their DNA. As a result of interbreeding, approximately one-third of their genetic makeup is made up of genes from another closely related species.

The study had place in an area close to Kenya’s Amboseli National Park, where yellow baboons occasionally meet and mix with their anubis baboons neighbors who live to the northwest.

researchers have been monitoring these animals on a near-daily basis since 32, noting when they mated with strangers and how offspring did resulted in their lifetime behavior as part of the Amboseli Baboon Research Project, one of the longest field studies of wild primates in the world.

Yellow baboons have yellow-brown fur with white cheeks and underparts. Anubis baboons have greenish-gray fur, and males have a shaggy mane around their heads. Although these are separate species that diverged 1.4 million years ago, they can hybridize where their ranges overlap.

By all accounts, the descendants of these unions are doing very well. Fifty years of observations have revealed no clear signs that the hybrids fare worse than their counterparts. Some even fare better than expected: Baboons that carry more Anubis DNA in their genome mature faster and form stronger social bonds, and males are more successful at gaining mates.

But new genetic findings published Aug. 5 in the journal Science suggest looks can be deceiving.

Research sheds light on the how species diversity on Earth is maintained even when genetic lineages between species are fuzzy, said Duke University professor Jenny Tung, who led the project with her PhD students Tauras Vilgalys and Arielle Fogel.

Interspecific mating is surprisingly common among animals, said Fogel, who is a doctoral student in the program. from Duke University in Genetics and Genomics. Some 20 to 30 % of great apes, monkeys and other primate species interbreed and mix their genes with others.

Even humans moderns carry a mix of now extinct dad and mom genes. As much as 2-5% of the DNA in our genomes indicate past hybridization with Neanderthals and Denisovans, ancient hominids our ancestors encountered and mated with during their migration from Africa to the United States. Europe and Asia. These bonds left a genetic legacy that still lingers today, affecting our risk of depression, blood clots, even tobacco addiction or complications from COVID-20.

Researchers wanted to understand the possible costs and benefits of this genetic mixture in primates, including humans. But modern humans stopped interbreeding with other hominins tens of thousands of years ago, when all but one species – ours – became extinct. The wild baboons of Amboseli, however, make it possible to study the hybridization of primates which is still in progress.

Researchers have analyzed the genomes of some 440 Amboseli baboons across nine generations, searching for DNA fragments that may have been inherited from Anubi immigrants.

They found that all baboons in the Amboseli Basin in southern Kenya today are a mixture, with anubis DNA representing approximately 37 % of their genomes on average. Some have anubis ancestry due to interbreeding occurring quite recently, within the last seven generations. But for almost half of them, the mixing happened further back, hundreds or thousands of generations ago.

Meanwhile, data shows that some pieces of Anubis DNA had a cost to the hybrids that inherited it, affecting their survival and reproduction such that these genes are less likely to appear in the genomes of their descendants today, said Vilgalys, now a postdoctoral fellow at the University of Chicago.

Their results are consistent with genetic research in humans, suggesting that our early ancestors also paid the price for hybridization. But exactly what Neanderthal and Denisovan genes did to harm them has been difficult to disentangle from the limited fossil and DNA evidence available.

Researchers say baboons of Amboseli offer clues to the costs of hybridization. By using RNA sequencing to measure gene activity in baboons’ blood cells, researchers have found that natural selection is more likely to weed out borrowed pieces of DNA that act as switches, activating and turning off other genes.

The next step, Fogel said, is to determine more precisely what ultimately affects these hybrid baboons’ ability to survive and reproduce. .

Genomic data allows researchers to look back many more generations and study historical processes that cannot be seen directly in the field, Vilgalys said.

“But you have to look at the animals themselves to understand what the genetic changes actually mean,” Tung said. “You need both fieldwork and genetics to understand the whole story.”

“We’re not saying that’s what Neanderthal genes and Denisovans have done in humans,” added Tung, now at the Max Planck Institute for Evolutionary Anthropology in Germany. “But the case of the baboon clearly shows that genomic evidence for the costs of hybridization can be consistent with animals that not only survive, but often thrive.”

This research has was supported by grants from the Nationwide Science Foundation (NSF IOS 088558, BCS-1751783, BCS-2018897, DGE #1644868), Countrywide Institutes of Overall health (R19AG053308, R20AG053330, P01AG031719,R19High definition088558, T32GM2016 ), the Leakey Basis, and the North Carolina Biotechnology Center (2016-IDG-1013).

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