E24 - How and when did animals first appear? Extraordinary new fossils from China

What (and when) is an animal? They are thought to have first arrived about 500 million years ago and immediately underwent an explosive diversifcation at the beginning of the Cambrian. When and how this important event took place has always been hard evolutionary problem to solve: fossils with the necessary preservation of soft-tissues are rare and limited. Two finds from China blow open new windows into this episode. 

The first is a new site from just before the Cambrian. It yields all sorts of typical Ediacaran weirdos, but preserved in a way that we don't usually get to s...