Book 33, Question 21
Why do mammals have lips and cheeks?
Lips and cheeks might seem ordinary, but they are special mammal features.
A newborn mammal needs to suck milk. Strong lips close around the mother’s nipple, and cheek muscles help make suction, like drinking through a straw. Reptiles and birds don’t drink milk this way. Lips and cheeks also help mammals chew, hold food, and make some sounds. Your lips started as a feeding tool.