More evidence for evolution: Some whales are born with legs which are remnants of when their ancestors were land animals. This is called an atavism which is of course explained in great detail at Wikipedia. Wikipedia is my friend.

Atavism: Evolutionarily, traits that have disappeared phenotypically do not necessarily disappear from an organism's DNA. The gene sequence often remains, but is inactive. Such an unused gene may remain in the genome for many generations. As long as the gene remains intact, a fault in the genetic control suppressing the gene can lead to it being expressed again.

Wikipedia - Atavism