Why Do We Have Fingernails and Not Claws?
Nails evolved from claws roughly 50 million years ago. Why did this happen and what purpose do nails serve?
Oldest evidence of nails in modern primates (Science Daily)
"From hot pink to traditional French and Lady Gaga's sophisticated designs, manicured nails have become the grammar of fashion. Scientists have now recovered and analyzed the oldest fossil evidence of fingernails in modern primates, confirming the idea nails developed with small body size and disproving previous theories nails evolved with an increase in primate body size."
Toe Fossil Contributes to a Head-Scratcher (The New York Times)
"Which came first, the nail or the claw? The answer is unclear, but researchers have discovered a clue: an early primate that had a toe bone with features of both a grooming claw and a nail. A fossil of the 47-million-year-old primate, Notharctus tenebrosus, had a lemur-like grooming claw on its second digit, but it was flattened, a bit like a nail, according to a new study in the journal PLoS One."
Evidence for a Grooming Claw in a North American Adapiform Primate: Implications for Anthropoid Origins (PLoS)
"Among fossil primates, the Eocene adapiforms have been suggested as the closest relatives of living anthropoids (monkeys, apes, and humans). Central to this argument is the form of the second pedal digit. Extant strepsirrhines and tarsiers possess a grooming claw on this digit, while most anthropoids have a nail. While controversial, the possible presence of a nail in certain European adapiforms has been considered evidence for anthropoid affinities."