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Mammals

What Is a Mammal?

Humans are mammals. The word mammal comes from the Latin mamma, meaning breast, because female mammals produce milk to nurse their babies. Nearly all mammals give birth to live young, and all are warm-blooded, maintaining a near-constant body temperature regardless of environmental conditions. They are vertebrates and use lungs to breathe air and are the only animals that grow hair. Mammals probably appeared on Earth some 200 million years ago.