Whales are highly-modified, once-hoofed mammals which are entirely aquatic. This is arguably one of the greatest of evolutionary punchlines. We just didn’t get the joke until relatively recently.

Upon viewing a whale skeleton, the fact that the animal once had terrestrial ancestors is not too difficult to detect – hints that their forerunners walked the prehistoric shoreline can be seen in the arrangement of the long, altered fingers which provide the framework for whale flippers, as well as the minute vestiges of hindlimbs and hips which are deeply embedded in whale bodies. Naturalists understood the relevance of these features to whale evolution long ago. The trouble was that the fossil record of whales was so poor that no one could be