Study: Hearing, smelling differ in man, chimps
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Chimps and humans share more than 99 percent of their genes.
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WASHINGTON (Reuters) -- Genes that fine-tune the sense of hearing and smelling in people may be important in separating humans from chimpanzees, according to U.S. researchers.
A comparison of the gene maps of humans and chimpanzees supports the idea that language is a key factor that makes us human, the team at Cornell University in New York and Celera Genomics found.
"Speech is considered to be a defining characteristic of humans," they wrote in their report appearing in Friday's issue of the journal Science.
They noted differences in genes believed to be involved in the development of speech.
"Several genes involved in the development of hearing also appear to have undergone adaptive evolution in the human lineage, and we speculate that understanding spoken language may have required tuning of hearing acuity," they wrote.
The team additionally found differences in genes that control production of receptors -- molecular doorways -- into cells involved in smell.
"It seems likely that the different lifestyles of chimps and humans might have led to divergent selection pressure on these receptors," they wrote.
Genes involved in fertilization and pregnancy were different as well, they found.
Scientists think chimps and humans diverged from a common ancestor 5 million years ago.
Humans and chimps share more than 99 percent of their genes, and scientists are eager to find out how tiny differences can be so important.
On Wednesday, U.S. researchers published a draft map of the entire chimpanzee genome and invited comparison.
But the gene maps of humans and chimps have been available as works in progress for years. The team at Cornell and Celera compared 7,600 key genes that chimps, mice and humans share.
To make sure the genes were important in distinguishing the species, they also compared many of the genes in different people. They found the chimp genes were 10 times as different.
"Human-chimp DNA sequence divergence is roughly 10 times the divergence between random pairs of humans," they wrote.
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