THANKS to Kamilah the gorilla, the last of the great apes has had its genome fully sequenced. The results highlight key similarities between us and gorillas – our second closest relatives after chimps.
Richard Durbin of the Sanger Institute in Cambridge, UK, led the international team that pieced together the western lowland gorilla (Gorilla gorilla gorilla) genome using several different sequencing techniques. The genome contains more than 3 billion pairs of DNA letters – roughly the same as humans – and includes about 21,000 genes.
Researchers can now compare the gorilla genome with chimpanzee and human genomes to study the origin of our species.
Early analysis suggests that the gorilla lineage splintered off from other great apes about 10 million years ago, some 3 million years before chimps and humans split. It’s no surprise, then, that chimps and humans have more in common: the sequences found in 70 per cent of great ape genetic material are more closely related in chimps and humans than in gorillas and either species.
But despite the ancient split, the remaining 30 per cent of Kamilah’s genome turned out to be more closely related to humans or chimps than those species are to one another, suggesting that genes continued to trickle between the three lineages after they split
Aylwyn Scally of the Sanger Institute says the most likely explanation is that gorilla ancestors interbred with the ancestors of humans and chimps, much like early modern humans and Neanderthals did.
The researchers also roughly sequenced an eastern lowland gorilla’s genome (Gorilla beringei graueri) to compare it with Kamilah’s. The two subspecies separated 1.75 million years ago and now live 1000 kilometres apart in Africa. Here, too, the genomes hint at occasional interbreeding.
That seems to be quite common, says Scally. “Fifteen million years ago [long before the great apes split] was a good time to be an ape,” he says, as the climate and vegetation facilitated their spread and diversification. But as the climate changed, populations fragmented, evolved separately, and the small splinter groups either died out or found creative ways to carry on, such as breeding with other groups.
In this brave new primate world, gorillas rapidly evolved into a distinct species. Kamilah’s genome shows that after gorillas split off from other apes, some 500 genes changed more rapidly than the rest. Many of these genes are involved in hearing and brain development, and are the same as those that evolved quickly in human ancestors after they split from chimps. Some had speculated that their rapid evolution in humans could explain why we evolved language and chimps did not. Kamilah’s genome has thrown cold water on that idea: the gorilla and human versions of the genes are nearly identical.