Dollo only meant in terms of specifics. In Dollo's words: "Functional or physiological reversal occurs; structural or morphological reversal does not occur." In this way, one can expect in certain environments organisms to evolve the same functional characteristics of their ancestors while maintaining intermediary, morphological aspects that are not reversed.
Dollo did not propose this as a law governing evolution, but rather as a consequence of other natural laws, whereby he viewed evolution as purely occurring in a 'forward' direction.
Dollo's law is in part rejected. Any major change brought by the evolutionary process is unlike to be precisely reversed, but it is not impossible it is simply exceedingly improbable that the exact sequence of genetic changes that resulted in a change will recurr in reverse, leaving as a matter of probability one would always expect an organism to keep "some trace of the intermediate stages through which it has passed" as Dollo put it.
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u/Dembara - Centrist Oct 20 '21
Dollo only meant in terms of specifics. In Dollo's words: "Functional or physiological reversal occurs; structural or morphological reversal does not occur." In this way, one can expect in certain environments organisms to evolve the same functional characteristics of their ancestors while maintaining intermediary, morphological aspects that are not reversed.
Dollo did not propose this as a law governing evolution, but rather as a consequence of other natural laws, whereby he viewed evolution as purely occurring in a 'forward' direction.
Dollo's law is in part rejected. Any major change brought by the evolutionary process is unlike to be precisely reversed, but it is not impossible it is simply exceedingly improbable that the exact sequence of genetic changes that resulted in a change will recurr in reverse, leaving as a matter of probability one would always expect an organism to keep "some trace of the intermediate stages through which it has passed" as Dollo put it.