http://www.nature.com/news/2006/060828/full/060828-5.html: "A newly discovered mystery gene may have helped build the modern human brain, researchers report today.

Scientists don't know what the gene does. But they do know that humans have more copies of it than chimpanzees, monkeys, rats and mice. And they know that the gene makes a protein that is found in the human brain. That suggests that it may help to give the human brain its unique ability to think and reason, they say. "