[FRIAM] Spandrel

[thompnickson2 at gmail.com]

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
ThompNickSon2 at gmail.com
https://wordpress.clarku.edu/nthompson/

-----Original Message-----
From: Friam <friam-bounces at redfish.com> On Behalf Of Prof David West
Sent: Saturday, March 13, 2021 6:04 PM
To: friam at redfish.com
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

On Sat, Mar 13, 2021, at 2:08 PM, thompnickson2 at gmail.com wrote:
> 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
> ThompNickSon2 at gmail.com
> https://wordpress.clarku.edu/nthompson/
> 
> 
> -----Original Message-----
> From: Friam <friam-bounces at redfish.com> On Behalf Of Prof David West
> Sent: Saturday, March 13, 2021 2:43 PM
> To: friam at redfish.com
> 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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