Dollo's Law


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Dollo’s Law

 

(the doctrine of irreversibility of evolution), a doctrine first clearly formulated in 1893 by the Belgian paleontologist L. Dollo. According to Dollo, an organism cannot revert, even in part, to its former state through which several of its ancestors have already passed. For example, land vertebrates in the course of secondary adaptation to life in water do not become fish again nor do they acquire the characteristics peculiar to fish (for example, gills). That is why ichthyosaurs, which became adapted to an aqueous environment, remained in all their structural features typical reptiles; similarly, whales remained mammals with their own special structural features.

References in periodicals archive ?
org/wiki/Dollo's_law_of_irreversibility) Dollo's law, after Belgian paleontologist Louis Dollo.
Scientists have differed on just how rigid Dollo's law could possibly be 6 whether it is merely an expression that it's statistically very unlikely that an animal could follow the same evolutionary path twice (regardless of direction), or just an expression of how treading down one path leaves the path not followed, and all of its branches, closed off forever.
But the tiny house mite appears to have diverged from Dollo's law, shedding the specialized parasitic lifestyle of its ancestors for a more generalized living feeding on skin flakes and other organic debris shed by humans.
Three of the species live closer to the surface and are more generalized morphologically than the other six, making this family an excellent model with which to test and falsify Cope's Law of the unspecialized and Dollo's Law of evolutionary irreversibility.
But, over the past two decades, many biologists have challenged Dollo's Law, often by using statistical tools to reconstruct trait evolution and ancestry by looking only at existing species and their present-day traits.
They found the methods flawed, prompting them to examine the challenges to Dollo's Law.
Fifteen years of studies have relied on these procedures to show that Dollo's Law is frequently violated.