From: "Dan'l Danehy-Oakes" 
Subject: RE: (urth) Liev's Postpostulate
Date: Wed, 15 May 2002 09:08:00 -0700

Jeff Wilson claims that

> Dollo's law is crap; it's violated by marine mammals, and 
> moths that alight on trees in once-polluted areas.

...well, no; it isn't. 

In the case of peppered moths, no lost organs are reappearing; 
the a:A balance of certain alleles is shifting due to natural
(or, I suppose, semi-artificial) selection. The "dark" genes
had always been present as a minority in the "gene pool," became 
a far more prominent proportion of the gene pool when industrial 
pollution caused the trees they sit on to become darker in color, 
and once again became less common as pollution control allowed
the trees to regain their former light color. The basic papers
on this, by Kettlewell's and Haldane, are both easily available
in the Oxford reader on "Evolution," edited by Mark Ridley.

In the case of marine mammals, what has happened is that the
lost organs have exactly failed to reappear -- all marine 
mammals still must come to the surface to breathe; no gills 
have reappeared. And, while the modified fins we call legs have
re-modified themselves to a more fin-like structure, this isn't
a case of anything lost reappearing. The only thing that might 
be considered as a reappearance is the dorsal fin on some marine
mammals; I don't know enough about how those evolved to give a
legitimate answer to this.

--Blattid


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