Brains shrink in humans, potentially causing a number of health problems and mental illnesses as people age, but do they shrink to the same extent in the closest living relatives to humans--the chimpanzees?
New research says no, making the extreme amount of brain shrinkage resulting from normal aging in humans unique.
Chet Sherwood, an anthropologist at The George Washington University in Washington, D.C., and a team of scientists from seven other U.S. universities put forward the question to see if comparable data on the effects of aging could be found in chimpanzees. Such data on regional brain volumes in chimpanzees was not available, until now.
The researchers--anthropologists, neuroscientists, psychologists, biologists, and veterinary professionals--used magnetic resonance imaging (MRI) to measure the space occupied by various brain structures in adult humans and chimpanzees, including the frontal lobe and the hippocampus, an area of the brain associated with short-term and long-term memory.
They found chimpanzees do not display significant loss, or atrophy, in the size of their brains and other internal structures as they age.
Instead, Sherwood and colleagues suggest that as humans evolved the ability to live longer, the result was a "high degree of brain degeneration" as people get older.
"We were most surprised that chimpanzees, who are separated from humans by only 6-8 million years of independent evolution, did not more closely resemble the human pattern of brain aging," said Sherwood. "It was already known that macaque monkeys, separated from humans by about 30 million years, do not show humanlike, widespread brain atrophy in aging."
The current issue of Proceedings of the National Academy of Sciences reports the findings. The National Science Foundation (NSF) partially funded the research.
Because humans and chimpanzees grow, develop and age on different schedules
|Contact: Bobbie Mixon|
National Science Foundation