evolutionary clock


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evolutionary clock

any means of estimating the time which has elapsed since the evolution of a form or structure. For example, DNA or protein sequences may have two different forms and the rate of change indicated by such sequences may be directly proportional to the elapsed time. Calibration of such ‘clocks’ may be made through comparison with the fossil record.
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In contrast with morphological evolution, which occurs at very different rates depending on selection pressure, molecular evolution, on certain occasions and under certain conditions, can act like an evolutionary clock. In other words the amount of change is proportional to the length of separation.
The problem today is to solve the riddle of reading the molecular evolutionary clock. Ultimately, this problem will be solved, and when it is, the molecular evidence will be shown to mesh with the fossil record - both, after all, deal with the same evolutionary progression, the same history of life!
"It's like an evolutionary clock ticking between rock, paper, scissors then back to rock," he said.
Mitochondrial DNA alterations may not tick away like hands on a reasonably accurate evolutionary clock, Howell maintains.
Continental drift and the use of albumins as an evolutionary clock. Nature 225:397-400.
On the one hand, we have invoked evolutionary history and an evolutionary clock (Kane and Culver 1991; Kane et al.
A potential solution is to use an argument based on an evolutionary clock and assume that the probability of a switch in a branch of a tree depends on the length of the branch.

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