Largest genetic chimpanzee study unveils how they’ve adapted to multiple habitats and disease
Jolie, of the Ngogo community in Kibale National Park, Uganda, and her baby. Photo by Kevin Langerbraber
Chimpanzees are humans' closest living relatives, sharing about 98% of our DNA. Because of this, scientists can learn more about human evolution by studying how chimpanzees adapt to different environments and fight off diseases.
A new international research project published in the journal Science has revealed how the genes that help chimpanzees live in forest or dry savannah habitats are the same genes that could protect chimps — and humans — from malaria.
“The close genetic similarities between the great apes (have) resulted in diseases jumping from apes to humans, such as with malaria and HIV/AIDS, so studying wild chimpanzees is extremely useful to (understanding) these and other shared infectious diseases in humans, and could help to develop new treatments or vaccines,” said Harrison Ostridge, lead author and postdoctoral researcher at University College London.
“Finding evidence of adaptation to malaria in chimpanzees linked to the same genes that affect malaria resistance in humans is striking from an evolutionary point of view, as it suggests there may be limited ways that we can evolve resistance to the malaria parasite.”
Scientists noninvasively gathered fecal samples from 828 different chimpanzees, including all four subspecies, from 52 sites. This endeavor was conducted as part of the Pan African Programme: The Cultured Chimpanzee, and the samples were collected from nonhabituated chimpanzees, meaning wild chimpanzees that have not been exposed to humans.
Kevin Langergraber, a primatologist at Arizona State University, was involved in the project and explained that habituation takes a very long time and is expensive and logistically difficult. While habituation works well for sites like his at Ngogo, this current study is unique because researchers were able to gather samples from a much larger geographical area.
“It’s only been about 15 to 20 years where we can now get large-scale genetic information looking at a lot of the genome,” said Langergraber, a research scientist at the Institute of Human Origins and an associate professor at the School of Human Evolution and Social Change.
He explained that obviously scientists aren’t going to get a cheek swab from a chimpanzee, and even with habituated chimps, there are risks associated with sedating them to try to get a blood sample (which would provide the highest-quality DNA). It's simply too dangerous for an endangered species.
“People get interested when they hear chimps are humans' closest living relatives,” Langergraber said. “But, sort of what blows people's minds is when you tell them that humans are chimps' closest living relatives. You might think, from a chimp's perspective, that their closest living relative is a gorilla, right? Because a gorilla looks a lot more like a chimp than a human does. However, chimps are more closely related to humans than they are gorillas.”
The scientists found evidence of genetic adaptation in genes related to certain pathogens (disease-causing microorganisms) among the chimpanzees living in forests, where there is a high concentration of pathogens, with the strongest evidence found in genes linked to malaria. This includes two genes that are also known to be responsible for adaptation and resistance to malaria in humans: GYPA and HBB, the latter being responsible for sickle cell anaemia in humans.
The findings suggest that malaria is likely a significant disease for wild forest chimpanzees and that adaptation to the malaria parasite has happened independently through changes in the very same genes in chimpanzees and humans.
Just as important as the genetic science for this article is the conservation efforts, said Aida Andrés, lead author and professor at University College London.
“There are just a few hundred thousand chimpanzees alive, but they are found across very different landscapes, from East Africa to the far west of the continent, including dense tropical rainforests and open areas of woodland and savannah,” Andrés said. “This makes them quite unique, because except for humans, all other apes live exclusively in forests. Here, we have shown that, besides acquiring behavioral adaptations, different chimpanzee populations have evolved genetic differences to survive in their different local habitats.
“As chimpanzees are facing threats across their range, including environmental changes to the climate and displacement due to human pressures, it is important that their genetic diversity is conserved to maintain their resilience and ensure the long-term survival of this intelligent and fascinating species.”
The article “Local genetic adaptation to habitat in wild chimpanzees” is published in the journal Science.
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