Monday, August 26, 2002

SPECIES DIFFERENCE IN BRAIN EXPANSION GENE

Gene Separates Early Humans from Apes
Mon Aug 26, 4:01 PM ET
By Maggie Fox, Health and Science Correspondent

WASHINGTON (Reuters) - A gene that separates humans from the apes and all other animals seems to have disappeared from humans up to three million years ago, just before they first stood upright, researchers said on Monday.

Most animals have the gene but people do not -- and it may be somehow involved in the expansion of the brain, the international team of researchers said.

The gene controls production of a sialic acid -- a kind of sugar -- called Neu5Gc, the researchers write in an advance online issue of the Proceedings of the National Academy of Sciences.

"This mutation occurred after our last common ancestor with bonobos (pygmy chimpanzees) and chimpanzees, and before the origin of present-day humans," they wrote. Neanderthal skeletons, the oldest early humans from who DNA has been obtained, also lack the sugar.

"It happens to be first known genetic difference between humans and chimpanzees where there is a major outcome," Ajit Varki of the University of California San Diego, who led the research, said in a telephone interview. "We are exploring the consequences of this."...