Human hand proportions are similar to those of some of our ancestors, suggesting that our hands did not evolve to serve the unique needs of modern humans.
Sergio Almécija at George Washington University in Washington DC and his colleagues analysed hand-length proportions in humans, apes (chimpanzee hand pictured), monkeys and fossil primates. They show that humans differ from living apes in overall hand proportions, but not from some of our ancestors, even when they accounted for differences in body size between species. Different primate species seemed to take their own evolutionary path to arrive at similarly long thumbs to improve hand dexterity.
The authors suggest that their evidence challenges the idea that contemporary apes are good morphological models of human ancestors.