As the researchers report today in PLOS Biology, the differences in metabolome profiles between the mice, monkeys, and chimps were no greater than the relatively small genetic differences between them, meaning that evolution had probably not significantly altered any of their tissues. Nor was there evidence of significant evolutionary changes in the human kidney or the visual or cerebellar cortex.
On the other hand, the metabolome profile of the human prefrontal cortex was dramatically altered from that of other primates: Using the split between the human and mouse (130 million years ago) and between humans and monkeys (45 million years ago) as baselines, the team calculated that the metabolome had evolved four times faster than that of the chimpanzee over the roughly 6 million years since the human and chimp lines split. (The genetic differences between the two species, in contrast, are only about 2%.)
This result was not shocking, given the mountains of evidence for the greater cognitive prowess of the human brain compared with that of other primates. But what did surprise the team was the differences in the profiles of primate and human skeletal muscle: The human metabolome had evolved more than eight times faster than that of the chimps since the two species went their separate evolutionary ways.
Can’t think why. (Note: A reader writes to say that the strength comparison was with monkeys and the metabolic one with chimps.)
See also: The Science Fictions series at your fingertips (human evolution)