Humans and other primates are outliers among mammals for having nails instead of claws. But how, when and why we transitioned from claws to nails has been an evolutionary head-scratcher. Now, new fossil evidence shows that ancient primates -- including one of the oldest known, Teilhardina brandti -- had specialized grooming claws as well as nails. The findings overturn the prevailing assumption that the earliest primates had nails on all their digits and suggest the transition from claws to nails was more complex than previously thought. Grooming in mammals is not just about looking good. Thick body hair is a haven for ticks, lice and other parasites -- possible health threats, as well as nuisances. It's one that has been retained in many primates. Lemurs, lorises, galagoes and tarsiers have nails on most of their digits and grooming claws on their second -- and in tarsiers, second and third -- toes. So, why did the ancestors of monkeys, apes and humans lose their grooming claws? One possible answer: because we have each other. The research suggests the loss of grooming claws is probably a reflection of more complex social networks and increased social grooming.
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