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Date: Wed, 15 May 2002 13:47:07 -0400 (EDT)
From: Mark Millman 
Subject: RE: (urth) Liev's Postpostulate


In sharks and bony fish the dorsal fin is part of the
skeleton, while the dorsal fins of cetaceans (and, for
that matter, of their reptile analogues the ichthyosaurs)
are not.  That fact alone is sufficient to demonstrate
that the cetacean dorsal fin is not a reappearance of a
previously lost organ.

But now we're straying off-topic; my apologies.

Mark Millman

On Wed, 15 May 2002, Dan'l Danehy-Oakes (Blattid) wrote:

> 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.
> [snip re:  peppered moths]
> 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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