S03 · E18
Birds
Oct 13, 199526m
Scientists believe that birds evolved from reptiles. Birds have backbones, and they lay eggs, but they’ve developed a unique feature that sets them apart from all other animals – feathers. Feathers are made of the same stuff human fingernails and hair are made from – a protein called keratin. Feathers, combined with lightweight bones, powerful wings and strong hearts let birds fly.
