Biology’s big bang had a long fuse: Animals started evolving long before showing up as fossils

Biology’s big bang had a long fuse: Animals started evolving long before showing up as fossils

A new effort to date the early history of modern animals finds a lot of evolutionary dawdling.

The last common ancestor of all living animals probably arose nearly 800 million years ago, a multidisciplinary research team reports in the Nov. 25Science. From that common ancestry, various animal lineages diverged and evolved on their own paths. Yet the major animal groups living today didn’t arise until roughly 200 million years later, in an exuberant burst of forms preserved in fossils during what’s called the Cambrian explosion.

Life's diversity snowballed when Earth froze

Life's diversity snowballed when Earth froze

Ancient animals may have started their drive toward explosive diversity back when the Earth was a giant snowball, new research suggests. A startling expansion in the diversity of life forms began about 540 million years ago, early in the Cambrian period. During this apparently sudden outburst, known as the Cambrian explosion, all the major groups of animals seemed to materialize rapidly. Scientists have debated the causes of this great flowering of life for centuries.