These baboons borrowed a third of their genes from their cousins

Recent genomic studies on wild baboons in southern Kenya show that the majority of them have DNA signs of hybridization. A third of their genetic composition is made up of DNA from another, closely related species as a result of interbreeding.

The study was conducted in an area close to Kenya's Amboseli National Park, where yellow baboons and their anubis baboon neighbors that dwell to the northwest occasionally interact.

The Amboseli Baboon Research Project, one of the longest-running field studies of wild primates in the world, has tracked these creatures almost daily since 1971, recording when they married with outsiders and how the progeny fared during their lifetimes.

The faces and undersides of yellow baboons are white, and their fur is yellow-brown. Male Anubis baboons have shaggy manes wrapped around their heads and have greenish-gray hair. Despite being separate species that split 1.4 million years ago, they are capable of hybridizing in areas where their ranges intersect.

All sources indicate that the children of these partnerships do well. No overt indications that hybrids perform worse than their counterparts have been found in fifty years of observations. Some even perform better than anticipated: Baboons with more anubis DNA content in their genome develop more quickly, create tighter social relationships, and mate more successfully.

However, recent genetic discoveries that were reported in the journal Science on August 5 reveal that looks might be deceptive.

The study, conducted by Duke University professor Jenny Tung and her PhD students Tauras Vilgalys and Arielle Fogel, gives light on how the variety of species on Earth is preserved even when the boundaries between species are hazy.

According to Fogel, a PhD candidate at the Duke University Program in Genetics and Genomics, interspecies mating is surprisingly frequent among animals. Apes, monkeys, and other primate species cross-breed and exchange genes in the range of 20% to 30%.

Even contemporary humans have a mix of DNA from ancestors who are no longer alive. As much when 2% to 5% of the DNA in our genomes suggests that our ancestors may have interbred with Neanderthals and Denisovans, two extinct hominins, as they moved from Africa into Europe and Asia. These relationships produced a genetic legacy that is still there now and influences our susceptibility to depression, blood clots, cigarette addiction, and COVID-19 issues.

The goal of the study was to comprehend the potential advantages and disadvantages of this genetic mixing in humans and other animals. But tens of thousands of years ago, when all but one species of hominin became extinct, modern humans ceased mating with other hominins. However, it is feasible to research continuing primate hybridization thanks to the wild baboons of Amboseli.

The researchers searched for DNA strands that may have been passed down from anubis immigrants by examining the genomes of about 440 Amboseli baboons spanning nine generations.

They discovered that all baboons living in southern Kenya's Amboseli basin today are a mix, with anubis DNA making up, on average, 37% of their genomes. Due to interbreeding that took place just seven generations ago, some people have anubis heritage. However, the mingling dates back hundreds to thousands of generations for over half of them.

The data from that period demonstrate that some anubis DNA variants had a price for the hybrids who inherited them, affecting their survival and procreation to the point where these genes are less likely to be found in the genomes of their descendants today, according to Vilgalys, a postdoctoral scholar at the University of Chicago.

Their findings are consistent with human genetic studies, which implies that our distant ancestors also paid a cost for interbreeding. However, the scant fossil and DNA evidence has made it difficult to determine precisely what Neanderthal and Denisovan genes did to hurt them.

The baboons at Amboseli, according to the researchers, provide information on the costs of hybridization. The researchers discovered that natural selection is more likely to cull out pieces of borrowed DNA that serve as switches, turning other genes on and off, using RNA sequencing to monitor gene activity in the baboons' blood cells.

The next step, according to Fogel, is to identify precisely what is ultimately impacting the capacity of these hybrid baboons to live and procreate.

According to Vilgalys, genomic data enables researchers to examine historical processes that were not readily visible in the field and go back many more generations.

But to really comprehend what genetic alterations actually entail, Tung said that one must look at the animals themselves. "To obtain the full picture, you need both fieldwork and genetics."

Tung, who is currently working at the Max Planck Institute for Evolutionary Anthropology in Germany, said, "We're not claiming this is what Neanderthal and Denisovans genes did in humans. "But the baboon instance shows that genetic evidence for costs to hybridization may be compatible with species that not only survive, but frequently flourish," the author writes.