Evolutionary Tree!
The animals in the evolutionary tree are Manatee, Elephants, Hyrayes, Phinos, Tapris, Whales, Even toed hoofed animals, Aardvarks, Primates, Tree-Shrews, Cologos, Bats, Tenrecs, Mole- Shrews, Hedgehogs, Carnivors, Pangolins, Pikas, Hares, Rodents, Elephant Shrews, Edentates, Armodillos, Marsupiats, and egg-laying animals.
Evidence!
There is a large genetic database. The position of the endothermy hair is evidence along with the hair! Also all living mammals give birth to live young!