Mutation Rate in Humans Is Slower than in Other Primates

Researchers have discovered that the human mutation rate is significantly slower than for our closest primate relatives. The findings, published yesterday in Nature Ecology & Evolution, may be important for estimates of when the common ancestor for humans and chimpanzees lived—and for conservation of large primates in the wild.

“Over the past six years, several large studies have done this for humans, so we have extensive knowledge about the number of new mutations that occur in humans every year,” says Søren Besenbacher of Aarhus University. “Until now, however, there have not been any good estimates of mutation rates in our closest primate relatives.”

Using whole-genome sequencing of families, it is possible to discover new mutations by finding genetic variants that are only present in the child and not in the parents. The scientists looked at ten chimpanzee, gorilla, and orangutan families and found more mutations in the offspring than would be expected based on the human data.

The higher mutation rate means that the number of genetic differences between humans and chimpanzees would have accumulated over a shorter period of time than currently estimated. If the new mutation rate for apes is applied, the researchers estimate that the speciation event that separated humans from chimpanzees took place around 6.6 million years ago. If the mutation rate for humans is applied, speciation should have been around 10 million years ago.

“The times of speciation we can now calculate on the basis of the new rate fit in much better with the speciation times we would expect from the dated fossils of human ancestors that we know of,” explains Mikkel Heide Schierup of Aarhus University. The reduction in the human mutation rate could also mean that we have to move our estimate for the split between Neanderthals and humans closer to the present.

Furthermore, the results could have an impact on conservation of the great apes. Christina Hvilsom from Copenhagen Zoo explains, “All species of great apes are endangered in the wild. With more accurate dating of how populations have changed in relation to climate over time, we can get a picture of how species could cope with future climate change.”