Researchers announce today that they have completed the genome sequence for the gorilla, the last genus of the living great apes to have its genome decoded. While confirming that mankind's closest relative is the chimpanzee, the team shows that much of the human genome more closely resembles the gorilla than it does the chimpanzee genome. This is the first time scientists have been able to compare the genomes of all four living great apes: humans, chimpanzees, gorillas and orangutans. This study provides a unique perspective on human origins and is an important resource for research into human evolution and biology as well as for gorilla biology and conservation.
"The gorilla genome is important because it sheds light on the time when our ancestors diverged from our closest evolutionary cousins. It also lets us explore the similarities and differences between our genes and those of gorillas, the largest living primate," says Aylwyn Scally, first author from the Wellcome Trust Sanger Institute. "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."
Kamilah, now a grandmother, was born on December 5, 1966, at the Woodland Park Zoo in Seattle and came to live at the San Diego Zoo Safari Park in January 1983. She has two surviving offspring: a female, Ndjia, and a son, Paul Donn. Her son has sired three offspring: a male now at the San Diego Zoo, a male now at the Knoxville Zoo in Tennessee, and a female now at the North Carolina Zoological Park in Ashboro, North Carolina.
The team searched more than 11,000 genes in humans, chimpanzees and gorillas for genetic changes important in evolution. Humans and chimpanzees are genetically closest to each other over most of the genome, but the team found many places where this is not the case: 15% of the human genome is closer to the gorilla genome than it is to the chimpanzee, and 15% of the chimpanzee genome is closer to the gorilla than to the human genome.
In all three species, genes relating to sensory perception, hearing and brain development showed accelerated evolution, particularly so in humans and gorillas.
This research also illuminates the timing of splits between species. Although species are commonly thought to diverge at a single point in time, this does not always reflect reality: species can separate over an extended period of time.
The team found that the divergence of gorillas from humans and chimpanzees occurred around ten million years ago. The split between eastern and western gorillas was much more recent, in the last million years or so, and was gradual, although 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. This research is informative about human evolution and highlights the importance of protecting and conserving the full diversity of these remarkable species.
"Availability of a gorilla genome sequence and knowledge of its variation among individuals and populations provide a significant new tool for increasing the understanding of aspects of the biology of these amazing apes that can be applied to conservation efforts on their behalf," said Oliver Ryder, Ph.D., director of genetics at the San Diego Zoo Institute for Conservation Research and a co-author of the paper.
Source : Zoological Society of San Diego