WEDNESDAY, Jan. 26 (HealthDay News) -- Orangutans have more diverse DNA than humans and it has remained relatively stable over 15 million years, say researchers who sequenced the genomes of six Sumatran and five Bornean orangutans.

Among the great apes, orangutans are the most distant cousins of humans. The international team of scientists found that the human and orangutan genomes are 97 percent identical. Human and chimpanzee genomes are 99 percent identical.

The researchers also documented immense genetic diversity (13 million DNA variations) within orangutans in Sumatra and Borneo. This diversity enhances the ability of populations to remain healthy and adapt to environmental changes.

"The average orangutan is more diverse -- genetically speaking -- than the average human. We found deep diversity in both Bornean and Sumatran orangutans, but it's unclear whether this level of diversity can be maintained in light of continued widespread deforestation," study author Devin Locke, an evolutionary biologist at the Genome Center at Washington University in St. Louis, said in a university news release.

He and his colleagues said they were surprised to find that, in some ways, the orangutan genome evolved more slowly than the genomes of humans and chimpanzees.

"In terms of evolution, the orangutan genome is quite special among great apes in that is has been extraordinarily stable over the past 15 million years," senior author and Genome Center director Richard K. Wilson said in the news release. "This compares with chimpanzees and humans, both of which experienced large-scale structural rearrangements of their genome that may have accelerated their evolution."

Orangutans, which are tree dwellers, are endangered in their native rainforests of Sumatra and Bornea. This research, published Jan. 27 in the journal Nature, may help conservationists determine the genetic diversity of wild and captive orangutan populations and also establish priorities for assisting subpopulations of orangutans based on their genetic health.

More information

The World Wildlife Fund has more about orangutans.