Morphological rates of change

Morphological rates of change - Morphological rates of...

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Morphological rates of change Observed rates of evolutionary change in modern populations must be greater than or equal to rates observed in the fossil record. Confirmation: Here I can do no better than to quote George C. Williams writing on this very issue: "The question of evolutionary rate is indeed a serious theoretical challenge, but the reason is exactly opposite of that inspired by most people's intuitions. Organisms in general have not done nearly as much evolving as we should reasonably expect. Long-term rates of change, even in lineages of unusually rapid evolution, are almost always far slower than they theoretically could be." ( Williams 1992 , p. 128) In 1983, Phillip Gingerich published a famous study analyzing 512 different observed rates of evolution ( Gingerich 1983 ). The study centered on rates observed from three classes of data: (1) lab experiments, (2) historical colonization events, and (3) the fossil record. A useful measure of evolutionary rate is the darwin, which is defined as a change in an organism's character by a factor of e per million years (where e is the base of natural log). The average rate observed in the fossil record was 0.6 darwins; the fastest rate was 32 darwins. The latter is the most important number for comparison; rates of evolution observed in modern populations should be equal to or greater than this rate. The average rate of evolution observed in historical colonization events in the wild was 370 darwins—over 10 times the required minimum rate. In fact, the fastest rate found in colonization events was 80,000 darwins, or 2500 times the required rate. Observed rates of evolution in lab
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Morphological rates of change - Morphological rates of...

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