I know it’s obvious to most people, but it’s only in the last ten years that I made the connection that mammals started on land and that at some point, some of them returned to water and became marine mammals. When I was young, there were fish, mammals, birds, reptiles, and yeah, btw, whales are mammals not fish but to me this was just a « fact » I had to know, some kind of "exception". In my head, it did not arise from evolution, there was no connection that fish and mammals were completely different things. I read that the current closest relative to whales is the hippopotamus. I do find it fascinating now that I have the big picture. Anyway. Thanks for coming to my Ted talk.