Manatees are part of the mammal group named Paenungulata, that share certain features with there distant relative, the elephant. The earliest known ancestor that had hind limbs is the Pezosiren, fifty million years ago, it was a creature like a large pig and stood around three feet high. Even though it could stand on land, it spent most of its time in water, like the present day hippo.

In the ancient times there was as many as thirty-five species in the Sirenia. Over years upon years, the hind legs of the Pezosiren disappeared and a flat tail used for swimming took its place. The fossils show that as the Sirenia evolved, it either had weak hind limbs or unnecessary external hind limbs. Of course modern manatees have only front flippers, no hind limbs and no hind flippers.

The manatees we know today have probably evolved from the Amazon region 2 million years ago and spread throughout the Caribbean, and then all the way up the coasts of Florida and West Africa.