Researchers have completed the great apes family's genetic library after they sequenced the genes of a western lowland gorilla, joining the already-sequenced genomes of humans, chimpanzees and orangutans. Scientists found that gorillas, which share 98% of their genes with humans, are a lot more related to humans than previously thought, as well as surprising genetic differences which went unnoticed until recently.
"Previously, people had some sort of picture based on ... probably one percent of the whole [gorilla] genome. So we now have a complete picture," said study co-author Richard Durbin, a geneticist with the U.K.'s Wellcome Trust Sanger Institute.
"Based on the comparisons between them, it helps us explore the evolutionary origins of humans and where we separated from other great ape species in Africa between six and ten million years ago," Durbin said.
The first step was taken in 2008, when the researchers sampled DNA from Kamilah, a 30-year old female western lowland gorilla, who was born in captivity and now lives at the San Diego Zoo Safari Park. Four years later, the researchers presented the complete genome, as seen published in this Wednesday edition of the journal Nature.
Gorillas - our close cousins
Their results show gorillas are are closer to humans than some might have thought. All of the members of the hominids family are considered to have descended from a common ancestor, some 10 million years ago. Around that time, human-chimp line split from the gorilla line, despite this however the team detected groups of gorilla genes that were surprisingly similar to human genes.
"Although [70 percent] of the human genome is indeed closer to chimpanzees, on average, a sizable minority of 15 percent is in fact closer to gorillas, and another 15 percent is where chimpanzees and gorillas are closest," said geneticist Aylwyn Scally, a study co-author also at the Wellcome Trust.
The new data shows that humans and gorillas are 98% genetically identical - most of our genes are very similar, or even identical to, the gorilla version of the same gene. However, there are few important differences which have been observed.
Insightful genetic differences
Some illuminating genetic differences have been found by the researchers. For instance, certain genes involved in sperm formation have become inactive or have been reduced in the gorilla genome compared with the human genome. This trait has been probably developed by humans in consequence of severe mating competition. Gorilla packs however most often include only one male and several females.
A common sight is that of gorillas walking with the help of their arms, basically stepping on their fists. The researchers discovered gorillas possess a gene that helps the animal's skin grow a tough layer of keratin, a protein found in hair and nails. This genes, the scientists suggest, lead to the development of tough knuckles.
What's maybe the most interesting and valuable piece of information discovered thus far by the researchers is that of certain genes shared by gorillas and humans that cause disease in our species, but not in our ape cousins. Some variants are linked to dementia and heart failure in humans, and are shared by both humans and gorillas, however the latter seem to be unaffected by the conditions. Future research sparked by this find might show promising medical applications.
"If we could understand more about why those variants are so harmful in humans but not in gorillas, that would have important useful medical implications," Tyler-Smith said.