Put a Spandrel in the Works
by MikeGeneOkay, let's get to the fun stuff in Fodor's essay:
History might reasonably credit Stephen J. Gould and Richard Lewontin as the first to notice that something may be seriously wrong in this part of the wood. Their 1979 paper, "˜The Spandrels of S. Marco and The Panglossian Paradigm: A Critique of the Adaptationist Programme', ignited an argument about the foundations of selection theory that still shows no signs of quieting. A spandrel is one of those more-or-less triangular spaces that you find at the junctures of the arches that hold up a dome. They are often highly decorated; painters competed in devising designs to fit them. Indeed (and this is Gould and Lewontin's main point), casual inspection might suggest that the spandrels are there because they provide the opportunity for decoration; that, an adaptationist might say, is what spandrels were selected for. But actually, according to Gould and Lewontin, that gets things backwards. In fact, spandrels are a by-product of an arch-and-dome architecture; decide on the latter and you get the former for better or worse. Arches were selected for holding up domes; spandrels just came along for the ride.
I assume that Gould and Lewontin got their architectural history right, but it doesn't really matter for the purposes at hand. What matters is that though spandrels survived and flourished, nothing at all follows about what, if anything, they were selected for. To a first approximation, you have spandrels if and only if you have a dome that's supported by arches; the two are, as logicians say, coextensive. Is it, then, that selection for arches explains why there are spandrels? Or is it that selection for spandrels explains why there are arches? It looks, so far, as though the story could go either way; so what tips the balance? Surely it's that domes and arches are designed objects. Somebody actually thought about, and decided on, the architecture of San Marco; and what he had in mind when he did so was that the arches should support the dome, not that they should form spandrels at their junctures. So that settles it: the spandrels weren't selected for anything at all; they're just part of the package. The question, however, is whether the same sort of reasoning can apply to the natural selection of the phenotypic traits of organisms, where there is, by assumption, no architect to do the deciding. If cathedrals weren't designed but grew in the wild, would the right evolutionary story be that they have arches because they were selected for having spandrels? Or would it be that they have spandrels because they were selected for having arches? Or neither? Or both?
Yes indeed, how does one tell?
Fodor then offers an example from biology:
There's a really lovely experiment that provides an example. The working hypothesis was succinctly summarised by Lyudmila Trut in American Scientist in 1999: "˜Because behaviour is rooted in biology, selecting for tameness and against aggression means selecting for physiological changes in the systems that govern the body's hormones and neurochemicals. Those changes, in turn, could have had far-reaching effects on the development of the animals themselves, effects that might well explain why different animals would respond in similar ways when subjected to the same kinds of selective pressures.' In the vocabulary I've been using: one might expect a galaxy of other phenotypic traits to be endogenously linked to tameness, and hence to free-ride on selection for it. Such properties would co-evolve with tameness even if they have little or no systematic effect on fitness; in effect there would be evolution without adaptation. Moreover, insofar as the genetic and physiological mechanisms that link tameness to its free-riders hold across a range of species, one might expect that selecting for tameness will have similar phenotypic by-products in creatures of quite different kinds.
The experimental investigation of these hypotheses involved forty years of inbreeding for tameness in thirty or so generations of silver foxes. The results are impressive. On the one hand, foxes that were bred for tameness also tended to share a number of other phenotypic traits. Unlike their feral cousins, they tend to evolve floppy ears, brown moulting, grey hairs, short curly tails, short legs and piebald coloration (in particular, white flashes). Inbreeding for tameness also had characteristic effects on the reproductive cycles of the foxes and on the average size of their litters. And these are all traits that other domestic animals (dogs, cats, goats, cows) also tend to have. An adaptationist might well wonder what it is about dogs, cats etc that makes curly tails good for their fitness in an ecology of domestication. The answer, apparently, is "˜nothing'. Curly tails aren't fitness enhancing, they just happen to be linked to tameness, so selection for the second willy-nilly selects the first.
If you didn't know tameness was being selected for, would you think the Blind Watchmaker was busy pruning away to produce floppy ears, brown moulting, grey hairs, short curly tails, short legs and piebald coloration?
I'll add some more in the next installment.
October 19th, 2007 at 5:48 am
Mike:
And you think adaptationists are not aware of indirect selection (because that's what we're talking about here)?
It's standard multivariate selection theory. If z is your n-dimensional vector of phenotypes (i.e. z=[z_1,...,z_n]) and G your n by n genetic variance covariance matrix (containing all pairwise genetic covariances g_ij between the n phenotypic traits), and W is your (standardized) fitness gradient vector (describing how fitness changes per unit change in each of the n phenotypes, i.e. with entries dW/dz_i, i=1..n), then the new z after selection is given by
z'=z+G W
This is just the multivariate version of the breeders equation R=h^2 S (R response to selection, h^2 the heritability of the trait and S the selection differential)
Now if the dW/dz_i are all zero except for dW/dz_1 (say z_1 is tameness), i.e. there is no direct selection on any of the other traits z_i (i>1), then the z_i's will change anyway after selection on z_1 if they are genetically correlated with z_1 (i.e. if the g_i1 != 0).
This has been known for decades, so Fodor isn't saying anything new really.
Comment by Raevmo — October 19, 2007 @ 5:48 am
October 19th, 2007 at 7:11 am
Where did I say I thought that?
Thanks for the information. So it's pretty easy to figure out what is being selected for and what are the free riders?
Comment by MikeGene — October 19, 2007 @ 7:11 am
October 19th, 2007 at 10:11 am
Simply put, does form follow function or does function follow form? The scientific materialist (i.e., philosphical naturalists) argue illogically that function follows form. And it shows that they haven't been reading their Plato, more specifically Euthyphro. Plato says "Is an object carried because it is in a state of being carried, or is an object in a state of being carried because it is carried?"
Likewise, does a plane fly because it has wings, or does it have wings because it can fly. There first needs to exist the formal idea of a craft whose lift from its wings exceeds the weight of the craft, then one gets planes that fly.
Information, thought recorded on matter, always exists for the sake of something else, some goal or end. -Platolives
Comment by platolives — October 19, 2007 @ 10:11 am
October 19th, 2007 at 11:50 am
Sorry, I am not getting the point of this. Are you suggest the mainstream model of evolution is in doubt if it is not easy to this out? Why would that be?
Comment by The Pixie — October 19, 2007 @ 11:50 am
October 19th, 2007 at 12:36 pm
Mike:
Ha, point taken. No, not so easy. You'd need some info on the G matrix (not so easy to estimate, but possible). If you know the correlated change in traits (delta z), and if you know G, then you can figure out the selection pressures, and hence the "free-riders":
W=inverse(G) delta z
Comment by Raevmo — October 19, 2007 @ 12:36 pm
October 19th, 2007 at 1:18 pm
I recommend Pigliucci and Kaplan (2006): Making Sense of Evolution discusses much of this subject , as well as what G-matrix analysis can and can't do.
Comment by Guts — October 19, 2007 @ 1:18 pm
October 19th, 2007 at 1:42 pm
I would suggest that one can challenge any aspect of Darwinian evolutionary theory as long as somewhere in the critique one espouses materialism or non-teleological explanations. If the article had said
instead of
the article would never had been published.
Despite this, the article is a great critique of natural selection.
Comment by Tom Mundie — October 19, 2007 @ 1:42 pm
October 19th, 2007 at 1:46 pm
Good point Tom.
The preceeding comment is superfluous to the matter being discussed but is revealing of the prevailing non-scientific view that dominates. And they complain about the Wedge.
Comment by Bradford — October 19, 2007 @ 1:46 pm
October 19th, 2007 at 1:58 pm
Hi, platolives,
They also have been remiss in reading Theaetetus.
Comment by AnaxagorasRules — October 19, 2007 @ 1:58 pm
October 19th, 2007 at 2:17 pm
Fodor:
A ludicrous assertion, supplied without any supporting arguments or evidence.
Tom:
Really? Why?
Comment by Raevmo — October 19, 2007 @ 2:17 pm
October 19th, 2007 at 2:26 pm
Raevmo:
The idea is that Selection theory can't decide which of the traits were selected for.
Comment by Guts — October 19, 2007 @ 2:26 pm
October 19th, 2007 at 2:38 pm
Guts:
Not always for sure, but that's due to a lack of information, not a problem with the theory.
Could it be that I have assumed incorrectly that you have actually read Pigliucci & Kaplan?
Comment by Raevmo — October 19, 2007 @ 2:38 pm
October 19th, 2007 at 2:43 pm
Raevmo:
Not as far as I can see.
Raevmo:
You completely misinterpreted Fodor in your first post, so I'm not surprised you may have misinterpreted Kaplan et. al.
Comment by Guts — October 19, 2007 @ 2:43 pm
October 19th, 2007 at 2:47 pm
Hi Pixie,
You are picking an argument with a ghost. As I read Raevmo's comments this morning, it sounded like he/she was saying this was a rather trivial exercise, so I asked. Nothing more, nothing less.
Look, despite all this defensiveness, Fodor's point stands. We all agree that adaptations exist. That is not the issue. The issue is the extent to which things that appear as adaptations are truly adaptations:
and
And this goes back to my question:
Comment by MikeGene — October 19, 2007 @ 2:47 pm
October 19th, 2007 at 3:18 pm
THE word adaptation, like nearly all the words which have come
into use in evolutionary discussions and have been bandied about
in controversy during the last seventy years, has acquired in the
course of time more than one meaning.
It is sometimes used for
the process of becoming adapted, necessarily a hypothetical process,
about which we can know nothing except by inference. I want
to use it here in a different sense ; for an observable fact, the state
of being adapted, of conformity between structure and function,
which can be recognized or appreciated by a sufficiently careful
examination of a living being, in just the same way as if we were
to examine any piece of mechanism, like a bicycle, without preconceptions,
as a child or a savage might examine it. We could,
with sufficient care and patience, see that the different parts, the
chain or the pedals or the bearings, were specially designed for
what they had to do, and would do it worse, or fail altogether, if
they were made differently.
As such, adaptation is an observable fact, and I believe it is no
exaggeration to say that it is the most striking and obvious fact
observable throughout the animal and plant kingdoms"¦
In general, adaptation is easy enough to notice, but very difficult
to observe or to describe properly. And the weight to be given
to adaptation as a general fact is not to be appreciated by the
attenuated abstracts which find their way into works of general
discussion, but only by following the full detail of the descriptions
and experiments published in those comparatively few cases which
have received the detailed investigation that they deserve.
http://digital.library.adelaid...
Comment by Rock — October 19, 2007 @ 3:18 pm
October 19th, 2007 at 3:24 pm
For rational systems of evolution, that is for theories which make at least the most familiar facts [apprehensible to a "child" or a "savage"] intelligible to the reason, we must turn to those that make progressive adaptation the driving force of the process.
http://digital.library.adelaid...
For rational systems of design, that is for theories which make at least the most familiar facts intelligible to the reason, we must turn to those that make progressive adaptation the driving force of the process.
If true then we must distinguish between rational theories of design and ID.
Comment by Rock — October 19, 2007 @ 3:24 pm
October 19th, 2007 at 4:13 pm
Raevmo:
Sorry, I didn't finish my sentence. In my opinion, the the article is a good critique of natural selection as the dominant process for the origin of species. That was Darwin's idea after all. The history of science has shown that we do not discard accepted theories easily. In fact, we will not discard them until we have a replacement. The evidence that the world is not flat was known for a hundred years before we discarded it for a new theory. I think Fodor is setting the stage for a book in which he will propose a new theory. Others has tried to supplant natural selection as the dominant theory to explain the origin of species and have failed.
Comment by Tom Mundie — October 19, 2007 @ 4:13 pm
October 19th, 2007 at 4:42 pm
Tom:
I don't know how you get that from the article. The article doesn't cite a single source. Let me give you a source:
http://www.pnas.org/cgi/conten...
Here's part of the abstract of that paper by Rieseberg et al (2002), PNAS 99, 12241-12245:
[emph mine]
Comment by Raevmo — October 19, 2007 @ 4:42 pm
October 19th, 2007 at 5:26 pm
Just a reminder that critique, although mostly used in a negative vein, can also mean to discuss all aspects of an issue.
Comment by Bradford — October 19, 2007 @ 5:26 pm
October 20th, 2007 at 11:50 pm
Raevmo,
Unfortunately it is common for some research scientists to oversell their data. It is true in this case. I respectfully submit that this study does not investigate phenotypic diversification as it claims. The data indicate that in a majority of cases where phenotypes change in one direction natural selection is the cause. This is not surprising. This study does not study speciation. Conclusions regarding speciation can only be made through speculative extrapolation.
Comment by Tom Mundie — October 20, 2007 @ 11:50 pm
October 21st, 2007 at 2:39 am
Tom Mundie wrote:
Yet the paper says:
Tom,
How do you account for this observation if directional selection is not the major cause of speciation?
Comment by keiths — October 21, 2007 @ 2:39 am
October 21st, 2007 at 4:31 am
Keiths:
In fact, the paper does not rule out prior directive, self-amplifying molecular mechanisms for the same pattern among many different traits, that would render selection secondary.
Comment by Guts — October 21, 2007 @ 4:31 am
October 21st, 2007 at 5:44 am
Guts,
You're missing the point. Tom grants the ability of directional selection to account for intraspecific phenotypic differences, but challenges the idea that they account for interspecific differences, labeling it a "speculative extrapolation":
The authors note that "interspecific trait differences were more strongly or consistently selected than intraspecific differences". I'm asking Tom why this pattern would obtain if directional selection were not the major cause of speciation.
Comment by keiths — October 21, 2007 @ 5:44 am
October 21st, 2007 at 5:52 am
Keiths:
And, not unexpectedly, you don't get it. Even if it can be said that selection of any adaptive trait in any lineage was due to directional selection, you can still not rule out prior directive molecular mechanisms that may be involved, which would render selection secondary.
Comment by Guts — October 21, 2007 @ 5:52 am
October 21st, 2007 at 6:25 am
You mean, apart from the utter lack of evidence for any "directive molecular mechanism" driving speciation?
Comment by keiths — October 21, 2007 @ 6:25 am
October 21st, 2007 at 6:29 am
Keiths:
No, there are plenty of cases where the evidnece of such direction is plentiful, such as the WNT case. And no doubt more research would uncover more.
Comment by Guts — October 21, 2007 @ 6:29 am
October 21st, 2007 at 6:52 am
Evidence that wnt genes drive speciation? Where?
I see. The research hasn't been done, but you can tell us categorically that if it were done, it would reveal evidence of a "directive molecular mechanism" driving speciation.
Comment by keiths — October 21, 2007 @ 6:52 am
October 21st, 2007 at 6:57 am
Keiths:
Yes that the complete set is now thought to be in the an LCA means that it was itself driving gastrulation, which in turn, indicates that this genetic complexity was necessary to create entoderm, ectoderm, establish a boundary between both layers, invent a mechanism to push one part of the body layer inside, etc. etc.
Keiths:
I'm not surprised you don't realize that a lot of this is informed assumption.
Comment by Guts — October 21, 2007 @ 6:57 am
October 21st, 2007 at 7:22 am
Why do you think that the presence of developmental genes in an ancestor indicates that subsequent evolution was directed?
Yeah, informed by prejudice and wishful thinking.
Comment by keiths — October 21, 2007 @ 7:22 am
October 21st, 2007 at 7:25 am
Keiths:
For the reasons I just indicated.
Keiths:
Hmm, I'm sure the authors of the paper would be offended by your assertion. Have any evidence?
Comment by Guts — October 21, 2007 @ 7:25 am
October 22nd, 2007 at 5:26 pm
"If true then we must distinguish between rational theories of design and ID."
ID theory must account for the observable ("most striking and obvious") fact. How is this accounting made? By the theory that God created it just so. "It just happened" = "It just so"
I'll take it as a test: Explain the "most striking and obvious" fact. Can ID "explain" anything, even the most commonly shared observation? No. Because a miracle wouldn't be a miracle if it occurred in the ordinary confluence of events.
Comment by Rock — October 22, 2007 @ 5:26 pm
October 22nd, 2007 at 5:40 pm
Keiths:
What makes you think that the existence of the genes themselves was a consequence of an undirected cause?
Comment by Bradford — October 22, 2007 @ 5:40 pm
October 23rd, 2007 at 12:01 am
Bradford,
What makes you think they weren't put there by a lagomorphic alien named Walter?
Comment by keiths — October 23, 2007 @ 12:01 am
October 23rd, 2007 at 12:39 am
Keiths:
Is Walter a code name for an unknown process in which atheists have unlimited faith? Keep the faith Keiths.
Comment by Bradford — October 23, 2007 @ 12:39 am