Consider the claw. Frequently found on animals around the world, it’s one of nature’s most versatile tools. Bears use claws for digging as well as defense. An eagle’s needle-like talons can pierce the skulls of their prey. Even the ancestors of primates used to wield these impressive appendages until their claws evolved into nails. So what caused this adaptation?

Learn more about Claws vs. Nails, keratin, and how the nails of our primate ancestors likely helped them thrive in the treetops with this TED-Ed lesson by Matthew Borths, directed by Augenblick Studios.

Next, find out where teeth come from, The Science of Skin, and why warm blood is better than cold.