The Fossil Problem Darwin Couldn't Solve

When Animal Life Seemed to Appear All at Once

Pick up a rock from a quarry in Yunnan, China, or from a mountainside in British Columbia, and with some luck you will find the imprint of an animal that lived more than half a billion years ago. It might have five eyes on stalks, or a spiked, segmented body, or a mouth ringed with teeth like a pineapple slice. These creatures are not ancestors of anything we can easily recognize. They look like experiments, and they turn up in rocks from a surprisingly narrow window of geological time.

That window is known as the Cambrian explosion. Before it, the fossil record shows mostly microbes and a handful of strange soft-bodied forms. Within a few tens of millions of years afterward, nearly every major body plan that we see in animals today had appeared: creatures with shells, legs, eyes, jaws, spines and early versions of a backbone. Charles Darwin saw the problem at once. In On the Origin of Species he admitted that the abrupt appearance of fossils in the lowest strata was a difficulty for his theory, and he said it might be urged as a valid argument against his views.

More than a century and a half later, the Cambrian explosion remains one of the most striking episodes in the history of life, and it still draws scientists, writers and believers who find in it a hint of something more than chance.

This article’s thesis is that the Cambrian explosion is a real and remarkable event, that scientists continue to debate its causes and exact timing, and that a reader of faith can reasonably find it consistent with the idea of a creative purpose behind life’s history. The fossils are a reminder that life’s story has a dramatic opening chapter, and that the ordinary mechanisms we understand do not yet fully account for its pace.