The Cambrian Explosion was a period of extraordinary evolutionary innovation and speciation about 500 million years ago. Broadly speaking, organisms during this period evolved from a single-celled ancestor to diverse metazoan forms with modern anatomical features, including the presence of nervous systems, differentiated cells, and segmented bodies. This occurred during a relatively short geologic timeframe—only 5 to 10 million years—displaying one of the most dramatic radiations of life recorded in the fossil record. The cause of the Cambrian Explosion, though debated by geologists and biologists, is thought to be due to the emergence of improved systems of communication, metabolic capabilities and defense mechanisms.

See also: abiogenesis, evolutionary computing, evolutionary psychology, origin of life, emergence