Book 33, Question 18
Why do your arm and a horse’s leg have similar bones?
Look at the bones of a human arm, a dog’s leg, and a horse’s leg.
They all have a long upper bone, two lower bones, a wrist, and finger-like bones. A horse’s leg bones are long, and it walks on one big toe, like the tip of your middle finger. This match shows that mammals came from a common ancestor, and bodies change to fit each way of life.