Washington University scientists led an international project to sequence the orangutan genome. The work is expected to aid conservation efforts and the study of human evolution. (Perry Van Duijnhoven/Carel Van Schaik)

Frontrunners

Orangutans More Genetically Diverse Than Humans

Among great apes, orangutans are humans’ most distant cousins. Now, an international team of scientists, led by the School of Medicine, ­decoded the DNA of a Sumatran orangutan. With this genome as a reference, the scientists then sequenced the genomes of five additional Sumatran and five ­Bornean orangutans.

Their research reveals intriguing clues about the ­evolution of great apes, including humans, and showcases the immense genetic diversity across and within Sumatran and Bornean orangutans. Diversity is important because it ­enhances the ability of populations to stay healthy and adapt to changes in the environment.

“The average orangutan is more diverse ­— genetically speaking — than the average human,” says lead author Devin Locke, PhD, a geneticist at ­the Genome Institute.

The scientists catalogued some 13 million DNA variations in the orangutans. This valuable resource can help conservationists assess the genetic diversity of orangutan populations.

The orangutan genome adds details to the evolutionary tree and gives scientists insights into the unique aspects of human DNA that set man apart from the great apes, their closest relatives. Overall, the researchers found that the ­human and orangutan genomes are 97 percent identical.

However, in a surprising discovery, the researchers found that at least in some ways, the orangutan genome evolved more slowly than the genomes of humans and chimpanzees, which are about 99 percent similar.

“In terms of evolution, the orangutan genome is quite special among great apes in that it has been extraordinarily stable over the past 15 million years,” says senior author Richard K. Wilson, PhD, director of the Genome Institute, which led the project. “This compares with chimpanzees and humans, both of which have experienced large-scale structural rearrangements of their genome that may have accelerated their evolution.”