Does the Cambrian Explosion pose a challenge to evolution?
The “Cambrian Explosion” refers to the appearance in the fossil record of most major animal body plans about 543 million years ago. The new fossils appear in an interval of 20 million years or less. On evolutionary time scales, 20 million years is a rapid burst that appears to be inconsistent with the gradual pace of evolutionary change. However, rapid changes like this appear at other times in the fossil record, often following times of major extinction. The Cambrian Explosion does present a number of interesting and important research questions. It does not, however, challenge the fundamental correctness of the central thesis of evolution.