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Perspective: Metazoan Complexity and Evolution: Is There a Trend?

Daniel W. McShea
Evolution
Vol. 50, No. 2 (Apr., 1996), pp. 477-492
DOI: 10.2307/2410824
Stable URL: http://www.jstor.org/stable/2410824
Page Count: 16
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Perspective: Metazoan Complexity and Evolution: Is There a Trend?
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Abstract

The notion that complexity increases in evolution is widely accepted, but the best-known evidence is highly impressionistic. Here I propose a scheme for understanding complexity that provides a conceptual basis for objective measurement. The scheme also shows complexity to be a broad term covering four independent types. For each type, I describe some of the measures that have been devised and review the evidence for trends in the maximum and mean. In metazoans as a whole, there is good evidence only for an early-Phanerozoic trend, and only in one type of complexity For each of the other types, some trends have been documented, but only in a small number of metazoan subgroups.

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