What Are Our Nails For?
Our nails are very useful. Our fingernails help us to pick small objects and to do fine work. They also protect the tips of our fingers and are very useful for scratching an itch. Many women like to enhance their fingernails with colorful nail polishes. The ends of our toes are protected by our toenails.
Our fingernails and toenails are made of the same tough material as the animals’ claws and hoofs. This material is called Keratin, which is also what our hair is made of. Our fingernails are constantly growing. They grow about two inches (5 centimeters) a year. Fingernails serve as a visual advertisement of a person’s health too. For instance, malnutrition can change the coloring of nails, while small pits in fingernails can signal the skin condition psoriasis.
We have fingernails because we’re primates, and nails are one of the features that distinguish primates, including humans, from other mammals. They are essentially flattened forms of claws. “Most mammals have claws, and they use them to grab onto things, to climb things, to scratch things, and to dig holes.”
Scientists suspect primates sort of lost their claws and fashioned broad fingertips topped with nails to aid in locomotion. While claws would have provided excellent grip as our mammalian ancestors clambered up large tree trunks, they would have been a nuisance for larger-bodied primates trying to grasp smaller branches while scrambling across tree canopies for fruits. Rather, primates developed broader fingertips made for grasping.
About 2.5 million years ago, fossil evidence suggests early humans first picked up stone tools, which is about the same time our ancestors also developed even broader fingertips than earlier primates. To this day, humans sport broader fingertips than other primates. Whether fingernails are an adaptation that helps to support broad fingertips or a side effect from the loss of claws is unclear.