Artist’s reconstruction of the ancient ocean ecosystem preserved in the Jiangchuan biota Xiaodong Wang A huge and beautifully preserved suite of fossils discovered in China has cast doubt on the idea that complex life flourished dramatically during a rapid burst of evolution known as the Cambrian explosion. This event, spanning roughly 541 million to 513 million years ago, is when most of the animal groups alive today are thought to have first appeared, along with a bizarre array of evolutionary experiments that later went extinct. In the preceding period, known as the Ediacaran, it was thought that life was much less complex. But that is contradicted by the new fossil site in Yunnan province, known as the Jiangchuan biota, which includes more than 700 fossils dating from 554 to 537 million years ago.…