Genes controlling hearing, the creation of knuckle pads and sperm formation have caught the interest of boffins who today published the first sequenced gorilla genome.
The data from the project, which sequenced over 140 billion base pairs over a five-year period, implies that in 30 per cent of its genome, the gorilla is closer to humans and chimpanzees than the latter are to each other. And although humans and gorillas share 98 per cent of the same DNA, the divergence reveals new insight into how gorillas have evolved.
“Gorillas live in groups with one male and lots of females, so there's not much opportunity for sperm competition,” explained Dr Chris Tyler-Smith, head of the human evolution team at the Wellcome Trust Sanger Institute and co-author of the gorilla study, published in Nature. “So it was quite interesting for us to see that some genes involved in sperm formation [including TEX14] had over time become inactive in gorillas or decreased in copy number.”
Elsewhere on the genome, genes associated with hearing showed accelerated evolution over millions of years. This had previously been observed in humans, with the implication that it was connected to language ability. The news that hearing genes evolved so rapidly in gorillas implies that they must play a broader role than previously thought.
Gorillas also appear to carry normal variants of genes that can cause forms of dementia and heart failure in humans. “If we could understand more about why those variants are so harmful in humans but not in gorillas,” said Tyler-Smith, “that would have important and useful medical implications.”
Tyler-Smith and team noted that the gene EVPL, which contributes to keratin formation on the skin, has also been rapidly evolving in gorillas. This is thought to be related to the fact that gorillas require much more keratin than humans, as it is used for their knuckle pads.
To make sure of these surprise findings, the team at Sanger performed extra validation tests. “At each position in the sequence we had a deep coverage,” said Dr Richard Durbin, joint head of human genetics at the Wellcome Trust Sanger Institute, “and that can give us a high confidence in the quality [of the data].”
The DNA in the project came primarily from Kamilah, a female western lowland gorilla, but also several other individuals. It shows that humans and gorillas diverged as species between six and 10 million years ago, but confirms that chimpanzees are the nearest great ape species to humans, having diverged less than 5.4 million years ago.
The project completes the quadrilogy of great ape gene sequences: the human genome was published in full in 2003, the chimpanzee genome in 2005 and the orangutan genome in 2011. ®