Posted by
Prof David West on
Mar 14, 2021; 2:40am
URL: http://friam.383.s1.nabble.com/Spandrel-tp7601069p7601077.html
Nick,
first apologies for arrogance in first reply. I should have said that I find the definition derived from Bonner to be more understandable — to me — and, I think, it offers an actual mechanism / rationale that is absent, again to me, than "elaboration of epiphenomenon." I am enjoying the essay and i see an interesting connection with Wegner's Arrival of the Fittest book. That means Jenny Q will have to read it because and I are working on a paper in that area.
davew
> Bonner's a great guy, but I think he's wrong on that, or you're wrong
> in interpreting him. The whole thrust of Lewontin and Gould's work is
> that there are developmental constraints in evolution. Even according
> to orthodox Darwinian theory, mutation is random, but only with respect
> to the opportunities a mutation affords. Nothing says that a mutation
> can' be predictable, yet random in this sense. Any "random" assertion
> requires a point of view from which the stated variable is random. Any
> geneticist can tell you which mutations are more likely than others.
>
> Nick
>
> Nick Thompson
>
> -----Original Message-----
> Sent: Saturday, March 13, 2021 6:04 PM
> Subject: Re: [FRIAM] Spandrel
>
> Nick, thank you. I get the metaphor but I think my “definition” is more
> correct than ‘elaboration of epiphenom’. I get that notion from an
> essay I am reading on randomness in evolution by John Tyler Bonner
>
> Davew
>
> > Hi Dave,
> >
> > Ok, since you are also a metaphor enthusiast, let me explain a
> > spandrel in terms of its root metaphor. A spandrel, originally, is a
> > decoration on the curved triangular spaces formed by the intersection
> > of two perpendicularly intersecting archways. The decorations are so
> > suited to their settings that one might imagine that the hallways were
> > designed to accommodate them, but, of course, it is they that are
> > suited to fit the spaces affording by the intersecting hallways. The
> > same confusion exists with the human nose. The nose is presumably
> > what was left over when the brain expanded, and the gut and the jaw
> > shrank. It has been elaborated since to accommodate its new position,
> > but the nose it self is the result of other adaptations, not of an
> > adaptation FOR a nose. The most graphic example, of course, of a
> > spandrel is the erectal and colored pseudopenis (hypertrophied
> > clitoris) born by the female stripped Hyena. It is not an adaptation
> > itself, but a consequence of powerful selection between female
> > genealogies for feeding competition at the kill, which has select for
> > high levels of testosterone in females. (The females are heavier than
> > the males, and, in general more nasty in every way
> > -- definitely examples of testosterone poisoning.) The coloration of
> > the pseudopenis is the spandrel-part, because selection has
> > subsequently led to its "decoration". Put another way, a spandrel is
> > a phenomenon which is an elaboration of an epiphenomenon.
> >
> > Does that help at all?
> >
> > Nick
> >
> > Nick Thompson
> >
> >
> > -----Original Message-----
> > Sent: Saturday, March 13, 2021 2:43 PM
> > Subject: [FRIAM] Spandrel
> >
> > A while back there was a lot of discussion of spandrels that I failed
> > to grasp.
> >
> > Is a spandrel a stable morphological trait that results from random
> > chance rather than natural selection?
> >
> > Or am I still ignorant.
> >
> > Davew
> >
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