[FRIAM] Spandrel
thompnickson2 at gmail.com
thompnickson2 at gmail.com
Sun Mar 14 14:02:58 EDT 2021
Dave, we both agree, I think, that one of the tests of understanding is the ability to explain an idea to an honest, persistent questioner. So it is MY understanding of spandrel that is at stake here, not yours. I have not looked any of what follows up. It is strictly from ambient knowledge, and I predict that by the end of the day, voracious reader that you are, you will know more about this subject than I. One of my great weakness as a scholar is that I like to play with the blocks I have, whole new technologies could arise in block-tower-building, and I would never know it. I hope that Jon Zingale, another voracious reader, will weigh in and update me.
The basic idea here, is “side effect” (aka epiphenomenon). Not all structures are the result of selection on that structure as we see it. Study this artifact:
The illustration is a bit wonky, but I have seen that toy, so I know it exists. If you see one in a yard sale please buy it for me, because neither Sober nor I can find one any more. The idea is that you put marbles of different sizes/colors in the top of the device (i.e., blue is large, red is smaller, etc.) and you shake it. The device sorts the balls for size, and because the different sized balls are also of different colors, it also sorts for color. Because we are color obsessed creatures, we tend to focus on the color-sorting, but the device itself “knows” nothing of color. Sorting for color is a “side effect” of sorting for size. Color “comes along with” size. It “falls out”. In the essay I am working on I call this relation an “epiphenomenal” relation, and I am writing about it because I think it is the source of all sorts of confusion in the vital sciences.
Now both Gould and Lewontin were/are? Developmental biologists. Thinking like theirs was the basis for the old/new field of “evo-devo”. The basic idea is genes don’t code for structures, they code for the relative speed or slowness of chemical events. So, start with a dog’s face say, where the nose is perched out on the end of the upper jaw. Now select for a larger brain size, while selection also for a vastly reduced dentition and jaw size. Bingo, you get a nose! Similarly with the hyena: select for a more aggressive female hyena, and BINGO you get a female with a penis. As Bob’s your Uncle!
The main point of Gould and Lewontin’s essay was to hammer home the idea that not all structures, however notable they may be to our eyes, are the result of selection on those structures as such. It was meant to be a counter to all of us who were, at the time, trying to explain the presence of a penis in female hyenas by all the good that this structure does for the female when she displays it in aggressive encounters. The fact is that both the display and the penis come about as an “unintended consequence” of the selection for high levels of the “aggression hormone”, testosterone. And there is tremendous evidence of countervailing selection against the hypertrophied penis because the females have to give birth through it with all of the horrific consequences that you can imagine.
No, the trouble comes for me when we begin to apply the metaphor of a “spandrel”. The spandrels of St. Marco are triangular shaped decorations that are drawn on the ceilings of hallways where two corridors meet. The triangular shape is necessitated by the geometry of intersecting corridors. They are so elegant that some (it’s said) have been tempted to explain the structures as designed to accommodate the drawings, but that is nonsense. The spaces are side effects of the intersection of the corridors, and the drawings have been made to accommodate to the spaces. But where I get confused, and where I may confuse you, is whether the spaces are the spandrels or the drawings. I think of the drawings as the spandrels, and since the drawings are definitely “adapted”, I think of a spandrel as a secondary adaptation built on a side effect. You might think of the spandrel as the space, in which case the spandrel is a structure created as a side effect of selection on one or more other structures.
So, think about arm pits. They are hairy, and glands in the armpit disperse pheromones. Is the shape of the armpit been selected for dispersing hormones? We can all agree that that idea is silly. The shape of the armpit is dictated by the needs of hanging an arm on a torso. We can also agree the modification of the sweat glands and the hair are plausibly “for dispersing” pheromones. What we may stumble over is whether the “spandrel” is the space where the hair and glands are located, or the hair and glands themselves. If you look spandrel up in Wikipedia you will see endless wrangling about the meaning on “spandrel” and I suspect that much of it can be sourced to this ambiguity of the metaphor.
Before I close, let me defend for a moment my use of the word epiphenomenon. One of most important uses of that word is to state a theory that consciousness is a side effect of the operation of the brain but events in consciousness are not in the causal chain of the processes that produce it. Now can we say that consciousness is a “spandrel”. Well it depends on where we came out on the ambiguity above. Is consciousnsess just the “space” created by the operation of the brain, and has nothing to do with its own form. Or has the fact of consciousness been seized upon by subsequent selection to give it causal properties. That is the language problem that I am trying to sort out.
I need to go get something to eat, but be fore I send this to you, I will try to steel-man what you wrote below in some larding.
Nick Thompson
<mailto:ThompNickSon2 at gmail.com> ThompNickSon2 at gmail.com
<https://wordpress.clarku.edu/nthompson/> https://wordpress.clarku.edu/nthompson/
From: Friam <friam-bounces at redfish.com> On Behalf Of Prof David West
Sent: Sunday, March 14, 2021 8:34 AM
To: friam at redfish.com
Subject: Re: [FRIAM] Spandrel
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?"]
[NST===>Well, this is the insight of evo-devo. Because development has to adapt to the vicissitudes of growing up, it has all sorts of buffering pathways that can be capitalized on by natural selection. So when a mutation occurs, these buffering pathways are called into action to permit, in so faras possible, a viable structure. Development (not genes) propose; selection disposes. <===nst]
One aspect of the original change, the nose, continues to change — is "decorated."[NST===>Selection goes to work on the structure that selection on other structures has provided.<===nst]
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.[NST===>Well, the fact of this flabby thing left hanging off the front of the face offers opportunities for further selection. <===nst]
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.[NST===>OHHHHH! I think I see the problem. Up till now, I have been arguing that the nose is not a “thing.” Now , suddenly I have to argue that it becomes a thing for the purposes of further evolution. Hmmm. I haven’t really thought about that before. I think my answer has to be that there are no such “things” in evolution. Mutations are never “for” structures; structures are altered by mutations because they alter the relative rates of developmental processes. A mutation that cannot cooperate with developmental process is lethal. You may have just stumbled on the problem which has been bothering me about evolution ever since I came to Santa Fe: if development is such a tangled network, how on earth do we separate out any one trait for selection. Selection requires genetic main effects, additive genetic variance; if all genetic effects are interactions, then Darwin’s theory is a non starter. But barnyard selection would also be a non-starter, so that non-starter argument is itself a non-starter. But here’s an odd thought I keep having: Could it be that selection – meta selection – has arranged for additive genetic variance SO THAT (ugh!#!!!) evolution can occur? <===nst]
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?
[NST===>No. What I see is how deep is your understanding of the fundamental problem of evolutionary theory – the isolation of variance. Not being a voracious reader I don’t know if anybody else has worried about that problem. It’s what attracts me to steve’s line of thought. If, in some way, complexity theory could explain the isolation of variance sufficient for natural selection to occur, I would be very grateful. <===nst]
Re arrogance: I think writing requires arrogance. I can’t imagine starting to write without the thought that I know SOMETHING, and that of course is an illusion.
Now, in haste.
Nick
davew
On Sat, Mar 13, 2021, at 9:21 PM, thompnickson2 at gmail.com <mailto: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
<mailto:ThompNickSon2 at gmail.com> ThompNickSon2 at gmail.com
<https://wordpress.clarku.edu/nthompson/> https://wordpress.clarku.edu/nthompson/
From: Friam <friam-bounces at redfish.com <mailto:friam-bounces at redfish.com> > On Behalf Of Prof David West
Sent: Saturday, March 13, 2021 8:41 PM
To: friam at redfish.com <mailto: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 <mailto: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 <mailto:ThompNickSon2 at gmail.com>
> https://wordpress.clarku.edu/nthompson/
>
> -----Original Message-----
> From: Friam <friam-bounces at redfish.com <mailto:friam-bounces at redfish.com> > On Behalf Of Prof David West
> Sent: Saturday, March 13, 2021 6:04 PM
> To: friam at redfish.com <mailto: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 <mailto:ThompNickSon2 at gmail.com>
> > https://wordpress.clarku.edu/nthompson/
> >
> >
> > -----Original Message-----
> > From: Friam <friam-bounces at redfish.com <mailto:friam-bounces at redfish.com> > On Behalf Of Prof David West
> > Sent: Saturday, March 13, 2021 2:43 PM
> > To: friam at redfish.com <mailto: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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