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Humans and chimps separated from a common ancestor six million years ago, while gorillas split off from that common ancestor four million years before that, confirms a new study, published in Nature.

Sixty scientists worked over five years to sequence the genome of a single female lowland gorilla. Their study published in the British journal Nature, confirms that humans and chimps separated from a common ancestor six million years ago, gorillas split off from that common ancestor four million years before that.

Lead author Aylwyn Scally, is with the Trust Genome Campus of the Wellcome Trust Sanger Institute in England, he says even with that evolutionary distance, humans and gorillas have a lot more in common, genetically, than previously thought.

"The passage of ancestry across the three genomes changes from position to position," Scally says. "Although most of the human genome is indeed closer to chimpanzee on average, there's a sizable minority, 15 percent is in fact closer to gorilla. And another 15 percent is where chimpanzee and gorilla are closest."

Ninety-eight percent of human and gorilla genes are identical; humans and chimps share 99 percent of their DNA. Co-author Chris Tyler-Smith, also with the Wellcome Trust Sanger Institute, says it's those relatively few genes that differ between the species that are of special interest.

For example, the study finds that a single gorilla gene associated with enhanced production of keratin - a protein that toughens the apes' fingernails, skin and especially their knuckle pads - is absent from the human genome.

Tyler-Smith says a group of genes, associated with hearing, tells another story.

"It's been known for some time that hearing genes in humans have shown accelerated evolution," he says, "but what we could see by sequencing the gorilla genome was that this acceleration goes back millions of years. So the implication of that is that this is not because of human language ability, it must be for some broader role that these play."

Tyler-Smith says the gorilla genome sequencing also identified several genes that in humans cause disease , but in gorillas do not. One gene leads to a form of human dementia, a second is associated with heart failure in people.

"If we could understand more about why those variants are so harmful in humans, but not in gorillas, that would have important or useful medical implications." Tyler-Smith says he intends to explore the ancestral family tree further, to learn what happened as humans and apes evolved on their separate paths.

He says the gorilla sequence is a template that will help to explain many of those evolutionary mysteries.

chimps: （非洲的）黑猩猩

gorilla: 大猩猩

keratin: 角蛋白；角素，角質

knuckle pads: 指節墊

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（來源：VOA 編輯：Rosy）