Cetaceans, the group including whales and dolphins, originated in south Asia more than 50 million years ago from a small, four-legged, hoofed ancestor. Now, researchers reporting the discovery of an ancient four-legged whale—found in 42.6-million-year-old marine sediments along the coast of Peru—have new insight into whales’ evolution and their dispersal to other parts of the world. The findings are reported in the journal Current Biology on April 4.