[FRIAM] Spandrel

[Prof David West]

Let me attempt to echo what i think I understand from your example and previous discussions where I lurked:

A mutation occurs in an organism resulting in an morphological change — i.e. a nose, modified jaw, and modified brain case.  I assume, *first potential error*, that this is a 'singular' change (e.g. a "face"), not three separate mutations and three different morphological changes to three different parts of the organism? [If there are three separate events, then how are they "coordinated?"]

One aspect of the original change, the nose, continues to change — is "decorated."

Second assumption (*error*): the same forces, mutation/selection, that cued the 'face' are prompting promulgation of new nose morphologies, the 'decorations'; which are selected among.

*Core misunderstanding*: it seems as if this demands some kind of "focused," on the nose, "micro-evolution." I do not see how such a weird phenomenon is _not_ required; but cannot fathom from whence, and how, it came.

If mutation/selection occurs only at the 'whole', i.e. the face, then I do not see why any aspect of that face is "isolated" such that localized change is deemed somehow independent of global change and therefore merits the label: spandrel.

Now that you see how deep I am in a well of misunderstanding, is rescue possible or is it time to pour in the cement and cap the well?

davew


On Sat, Mar 13, 2021, at 9:21 PM, thompnickson2 at gmail.com wrote:
> Well, “elaboration of an epiphenomenon” was not the core of the mechanism I described.  It was a fancy little idea I added at the end.  So what about the mechanism that I described was difficulty to undertad.

>  

> n

>  

> Nick Thompson

> ThompNickSon2 at gmail.com

> https://wordpress.clarku.edu/nthompson/

>  


> *From:* Friam <friam-bounces at redfish.com> *On Behalf Of *Prof David West
> *Sent:* Saturday, March 13, 2021 8:41 PM
> *To:* friam at redfish.com
> *Subject:* Re: [FRIAM] Spandrel

>  

> 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

>  

>  

> On Sat, Mar 13, 2021, at 5:37 PM, thompnickson2 at gmail.com wrote:

> > 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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