Gorillas more closely related to us than thought

Researchers have completed the genome sequence for gorillas – the last of the living great apes to have its genome decoded. The researchers confirmed that the chimpanzee is our closest relative, but it turns out that about 15 percent of the human genome map more closely resembles the gorilla genome than the chimpanzee’s. The study was published in the journal Nature on March 7, 2012.

Researchers used DNA from a female lowland gorilla named Kamilah. The 2012 gorilla DNA map completes a basic genetic library of the great apes. The human genome project was completed in 2003, the chimpanzee gene map was published in 2005, and the orangutan genome was completed in 2011. Now that the gorilla genome has been sequenced, scientists can compare genomes to learn how the great apes differ from each other and from us.

Aylwyn Scally, of the Wellcome Trust Sanger Institute, is the paper’s first author. He said:

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 team searched more than 11,000 genes in human, chimpanzee and gorilla for genetic changes important in evolution. They found that although humans and chimpanzees are genetically closest to each other over most of the genome, 15% of the human genome is closer to the gorilla genome than it is to chimpanzee, and 15% of the chimpanzee genome is closer to the gorilla than human.

In all three species, genes relating to sensory perception, hearing and brain development showed accelerated evolution – particularly in humans and gorillas.

Dr. Chris Tyler-Smith, senior author from the Wellcome Trust Sanger Institute, said:

We found that gorillas share many parallel genetic changes with humans including the evolution of our hearing. Scientists had suggested that the rapid evolution of human hearing genes was linked to the evolution of language. Our results cast doubt on this, as hearing genes have evolved in gorillas at a similar rate to those in humans.

Some genes tied to dementia and heart failure in humans appeared roughly the same in both humans and gorillas, but are not harmful to gorillas.

Another difference that stuck out was in the genes involved in sperm production. Tyler-Smith said:

Gorillas live in groups with one male and lots of females, so there’s not much opportunity for sperm competition. It was interesting for us to see that some genes involved in sperm formation…had either become inactive in gorillas or had decreased in copy number.

This research also illuminates the timing of splits between species. According to the paper, gorillas diverged from humans and chimpanzees around ten million years ago. In the last million years, eastern and western gorillas gradually split, and they are now genetically distinct. This split is comparable in some ways to the split between chimpanzees and bonobos, or modern humans and Neanderthals.

Gorillas survive today in just a few isolated and endangered populations in the equatorial forests of central Africa. They are severely threatened and their numbers are diminishing.

Bottom line: A paper in the journal Nature on March 7, 2012 describes the results of the first complete genome sequence for the gorilla – the last of the living great apes to have its genome decoded. The researchers confirmed that the chimpanzee is our closest relative, but it turns out that about 15 percent of the human genome map more closely resembles the gorilla genome than the genome of the chimpanzee.