Why do baleen whales have teeth and body hair while they are embryos, but not as adults?
Those characters show that baleen whales evolved from ancestors that had hair and teeth. Add to that the fact that whale embryos don’t form a blowhole directly: instead, they first form 2 nostrils just about the mouth – like land mammals begin with and have as adults – that then must migrate to the top of the head anf fuse to form the blowhole. Add to that the fact that whale embryos form hindlimb buds, and adult whales have vestigial bones in the pelvis region. Add to that the fact that an adult whale’s flipper skeleton is homologous to our arm and hand skeleton, with one upper arm bone, two forearm bones, a cluster of wrist bones, and finger bones. All of those taken together show that whales evolved from certain typical 4-legged land mammals; mammals with a full coat of hair, teeth, 2 nostrils just above the mouth, hindlimbs as well as forelimbs, and limb skeletons just like those of humans, cats, dogs, etc. And then, of course, we also have the fossil record confirming the evolutio
