Genome Research on Gorillas Sheds New Light on Human Evolution

The evolution of gorillas and humans diverged about 10 million years ago, study confirms.
A research team from the Wellcome Trust Sanger Institute have concluded that there are more similarities between the genomes, or genetic makeup, of humans and gorillas than previously known, and that their respective evolutionary lines diverged approximately 10 million years ago, consistent with interpretations of the fossil record. Their finds confirm that, although the human and chimpanzee are more closely related genetically, there are portions of the human genome that more closely resemble the gorilla genome than they do that of the chimpanzee.

Says Aylwyn Scally, senior author of the study, "The gorilla genome is important because it sheds light on the time when our ancestors diverged from our closest evolutionary cousins. It also lets us explore the similarities and differences between our genes and those of gorilla, the largest living primate. Using DNA from Kamilah, a female western lowland gorilla, we assembled a gorilla genome sequence and compared it with the genomes of the other great apes. We also sampled DNA sequences from other gorillas in order to explore genetic differences between gorilla species."

The researchers analyzed over 11,000 human, chimpanzee and gorilla genes to identify genetic changes that are key to evolution. They discovered that, while humans and chimpanzees are still genetically closest to each other for most of the genome, there are a significant number of places along the genome where gorillas and humans more closely match. Specifically, about 15% of the human genome resembles the gorilla genome more closely than that of the chimpanzee's. On the other hand, about 15% of the chimpanzee genome more closely parallels the gorilla's than the human's. In combination, findings like this have been interpreted to suggest a kind of "smoking gun" for the existence of a common ancestor for humans, chimpanzees, and gorillas. The study confirms that the respective evolutionary lines of gorillas and humans diverged approximately 10 million years ago. It is thought that chimpanzees and humans diverged about 4.5 - 8.0 million years ago.

Additional findings included indicators that the split between the eastern African and western African gorillas was much more recent, occurring within the last million years, and that the process was gradual. This gradual split may have implications for understanding the divergence among other apes and humans as well, such as between the ape line and the human line, between chimpanzees and bonobos, and modern humans and Neanderthals.

"Our research completes the genetic picture for overall comparisons of the great apes," says Dr Richard Durbin, a senior member of the research team, "After decades of debate, our genetic interpretations are now consistent with the fossil record and provide a way for palaeontologists and geneticists to work within the same framework."

The detailed report of the findings is included in the paper, Scally et al, Insights into hominid evolution from the gorilla genome sequence, 
published in Nature, March 8, 2012 (DOI: 10.1038/nature10842).

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