The so-called ‘Cambrian explosion’ that occurred 500-600 million years ago saw the appearance in the fossil record of an extraordinarily wide diversity of life forms. Whether there was a sudden flurry of evolutionary advances at the time or whether that time marked the beginning of animal bodies that were fossilizable and so gave the illusion of an explosion of life forms is not clear. The suspicions are that it was the latter.
The illustrations in a new book about that period show some reconstructions of them. We could well be the descendants of one of these animals. What is clear is that we had, by current standards, some pretty weird looking ancestors,. Here’s one of them that I thought most closely resembles me.