Gorilla genome reveals closer connection to humans

It has long been held that our closest evolutionary relative is the chimpanzee, with the gorilla taking its place as our second cousin.

Now a new analysis of the genome of the western lowland gorilla (gorilla gorilla gorilla) has shown portions of its genome are closer to us than we are to chimps.

This somewhat surprising finding sheds light on the machinations of evolution that have seen our species branch away from the other great apes.

The researchers, led by Richard Durbin and Alywyn Scally from the Wellcome Trust Sanger Institute in the UK, used second generation genome sequencing to compile an accurate assembly of the western lowland gorilla and synthesised it with data previously acquired on other gorilla sub-species.

They then compared the gorilla genome with those of humans and chimpanzees to identify similarities and differences and establish times when the species diverged.

They found that around 30 per cent of the gorilla genome – mostly non-coding regions – is closer to either humans or to chimpanzees than humans or chimps share with each other. This suggests in some aspects the gorilla is a closer relative to humans and chimps than humans are to chimps.

This somewhat unusual finding is made possible by the convoluted dynamics of evolution and the fuzziness of speciation, which is rarely a clean cut affair.

Instead, when two or more speciation events occur in close proximity, some of the genetic sequences can be mixed into the various lineages through a process called incomplete lineage sorting.

Based on this detailed view of the gorilla genome along with fossil evidence, the study authors estimate that the last human-chimpanzee-gorilla ancestor lived between 8.5 and 12 million years ago, and the human lineage split from chimpanzees between 5.5 and 7 million years ago.

The authors close by reinforcing the call for conserving gorilla populations lest we lose a close relative that can shed light on our species’ own evolutionary past.

“As well as teaching us about human evolution, the study of the great apes connects us to a time when our existence was more tenuous, and in doing so, highlights the importance of protecting and conserving these remarkable species,” they write.

The paper was published in Nature today.