Do All Primates Have Brains That Shrink with Age?

A team of neuroscientists, anthropologists, and primatologists have put their heads together to try to explain why humans are uniquely vulnerable to age-related dementia and diseases such as Alzheimer’s. They studied the brain sizes of a group of people of varying ages and compared that data with the brain sizes of chimpanzees that were bred in captivity. The researchers found that the human brain tends to shrink during the aging process, while the brain of our closet primate relative, the chimpanzee, does not. Although the reasons for this difference are complex, they are likely to be linked to the human life span, which extends long beyond our prime reproductive years. The large amount of energy required to maintain our large brains (which are three times larger than those of chimpanzees) into old age may explain why they ultimately shrink. The findings were published in the journal Proceedings of the National Academy of Sciences.

How age affects the human brain:

• The researchers focused on changes in the frontal lobe and hippocampus, the most shrink-prone regions of the human brain.
• As humans reach old age, their brains shrink in size by 10 to 15 percent. In chimps of equivalent age, their brains showed no shrinkage at all.
• Humans are the only beings on Earth that contract brain maladies such as Alzheimer’s disease, which afflicts nearly 50 percent of Americans over the age of 85.