BBC News uncovers a strange complex of problems that humans have and chimps don’t. We get old. On the one hand, we live a long time. And on the other, our brains shrink:
Anthropologist Chet Sherwood from George Washington University in Washington DC, who led the study, thinks that humans live longer to “pay for” their larger-brained children.
Humans live relatively long compared to other great apes. The majority of this extended life is post-menopausal, while chimps are reproductively viable right up to their death.
A human brain is three times the size of chimpanzee’s.
And it is not such a stretch, Dr Sherwood suggests, to conclude that grandparents’ extended lives are in an evolutionary sense there to relieve mothers from being solely responsible for raising their big-brained, energetically costly infants.
“I say this right now, as my seven year old daughter is being looked after by my mother,” he told BBC News.
“Because neurons cannot regenerate, aging, he thinks, is just the stress of living long enough to lend a helping hand to some relatives.”