Other than helping to boost the economy (U.S. nail polish sales reached $768 million in 2012, reported WWD), fingernails help highlight a key difference between primates and other mammals. Most mammals have claws—our nails are just a flattened version. Where our ancestors used fingernails to grasp fruit and branches, today, we use them to snatch little things like coins or paper. Fingernails may also serve as a window to our health: Discoloration or small pits can signal trouble like malnutrition or certain skin conditions.
