Health: Brain Shrinkage: It's Only Human

Human brains shrink as people grow old, unlike even our closest animal relative, says a new study in the Proceedings of the National Academy of Sciences that highlights what researchers call the unique character of human aging.

The human brain normally can shrink up to 15% as it ages, a change linked to dementia, poor memory and depression. Until now, researchers had assumed this gradual brain loss in later years was universal among primates.

But in the first direct comparison of humans to chimpanzees, a brain-scanning team led by George Washington University anthropologist Chet Sherwood found that chimpanzees don't experience such brain loss. From that, researchers concluded that only people are afflicted by this oddity of longevity.

For more, see Brain Shrinkage: It's Only Human by Robert Lee Hotz, July 26, 2011 at WSJ.com.