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Science 25 October 1996:
Vol. 274. no. 5287, pp. 473 - 0
DOI: 10.1126/science.274.5287.473a
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This Week in Science

Animals suddenly first appear in the fossil record at the dawn of the Cambrian, about 565 million years ago. The fossil record has generally been interpreted as evidence of a rapid evolution over a few tens of millions of years. Wray et al. (p. 568; see the Perspective by Vermeij, p. 525) examined this notion by determining rates of molecular sequence divergence among metazoan phyla. The data suggest that animals may have instead arisen about 1 billion years ago and that the radiation was prolonged.




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Science. ISSN 0036-8075 (print), 1095-9203 (online)