The initial phases of animal evolution proceeded faster than hitherto supposed: New analyses suggest that the first animal phyla emerged in rapid succession – prior to the global Ice Age that set in around 700 million years ago.
The fossil record reveals that almost all of the animal phyla known today had come into existence by the beginning of the Cambrian Period some 540 million years ago. The earliest known animal fossils already exhibit complex morphologies, which implies that animals must have originated long before the onset of the Cambrian.