Rates of evolution - How do we measure the rate of evolution?
Is the rate of evolution determined by selection?
Rates of evolution in the fossil record have been measured for many characters, in many species, at many different geological times. Are the rates of change in the fossil record consistent with the mechanisms of evolutionary change studied by population geneticists?
While we cannot prove that selection is responsible for changes in the fossil record, we can find out whether the results of research in the two areas are consistent. If for example, the fossil evolution rates are significantly higher than rates observed in artificial selection experiments, it would suggest that selection cannot be the only cause of evolution.
In fact, the rates of evolution observed in artificial selection experiments are far higher than those measured in fossils. We can conclude that the known mechanisms of population genetics, natural selection and random drift (though it is questionable whether drift is important in morphological evolution) can comfortably accommodate the fossil observations.
This labrador dog evolved after only a few thousand years of artificial selection: similar evolutionary changes in nature take many millions of years.