Genome Reveals Humans, Gorillas More Alike Than Previously Thought
March 8, 2012

Genome Reveals Humans, Gorillas More Alike Than Previously Thought

Researchers who have completed the genome sequence of the gorilla have discovered that the species is more genetically similar to humans than they had previously thought.

The study, which was led by researchers at the UK's Wellcome Trust Sanger Institute and the Baylor College of Medicine (BCM), looked at DNA from a 30-year-old female western lowland gorilla from the San Diego Zoo named Kamilah, Dave Mosher of National Geographic News reported on Wednesday.

They began studying the genome in 2008 and completed their work four years later, publishing their findings in the journal Nature.

In a March 7 press release, officials from the Wellcome Trust Sanger Institute said that the gorilla was the last of the great apes -- a group which also includes fellow primates chimpanzees, orangutans, and mankind -- to have their genome sequenced, thus completing "a basic genetic library" of these creatures.

"The gorilla genome is particularly important for our understanding of human evolution, because it tells us about this crucial time when we were diverging from our closest living relatives, the chimpanzees," researcher Aylwyn Scally of the Wellcome Trust Sanger Institute said a press conference announcing the findings, Stephanie Pappas of LiveScience reported in an article.

According to Kate Kelland of Reuters, the study confirmed that chimpanzees are still the closest genetic relative to humans, but that approximately 15% of the human genome is actually closer to that of the gorilla than the chimp. Humans and chimpanzees share in excess of 98% of their genes, Guardian science correspondent Alok Jha noted, while humans and gorillas share more than 96% of their genes.

The researchers looked at more than 11,000 genes in humans, chimpanzees, and gorillas during their research, the Wellcome Trust Sanger Institute said, and Chris Tyler-Smith, head of the human evolution team there and senior author of the study, told Bloomberg's Elizabeth Lopatto that the findings could have "useful medical implications."

Essentially, if scientists can track differences in how each of the species adapted to shared genetic characteristics over time, they could be able to determine why some diseases are harmful to humans but not other great apes, he suggested. For example, the authors have already observed that some genes that cause adverse conditions in people, including one responsible for a form of dementia and another that causes a thickening of the heart muscles known as hypertrophic cardiomyopathy, does not seem to have the same affect on gorillas, he told Lopatto.

Their work has also uncovered similarities in the genes responsible for hearing and sensory perception, and they have also observed brain development that suggests accelerated evolution in humans, apes, and chimps, Jha said.

"Our most significant findings reveal not only differences between the species reflecting millions of years of evolutionary divergence, but also similarities in parallel changes over time since their common ancestor," Tyler-Smith said in a statement.

"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," he added. "Our results cast doubt on this, as hearing genes have evolved in gorillas at a similar rate to those in humans."

The researchers believe that the divergence of gorillas from other great apes occurred approximately 10 million years ago, and among other changes, they noticed that DNA linked to the proteins that cause skin to harden were far more active in gorillas, which the Guardian reporter says could help explain the "large, tough knuckle pads" that allow the great apes to walk on their hands.

Pappas also wrote that the researchers discovered that selected genes that are involved in the production of sperm had become inactive or had been reduced in the gorilla genome when compared to human DNA. Tyler-Smith told her that this change was likely due to the fact that gorillas live in one male-one female communities, meaning that there is little competition among males for their reproductive fluids.

"The big picture is that we're perhaps 98 percent identical in our sequences to gorillas. So that means most of our genes are very similar, or even identical to, the gorilla version of the same gene," Tyler-Smith told Mosher. "But it's the few that differ that are of particular interest here."

"This doesn't change the overall view of evolution, and the overall tree is still the same. What this does show is that each branch has its own complexities and challenges," added Richard Gibbs, a geneticist with the BCM Human Genome Sequencing Center who was not involved in the study. "It means within each branch things can happen. We can't just conform to a simple tree on a gene-by-gene basis."


On the Net: