This essay pressuposes that Jerry Fodor's hatchet-job on Darwin in Fodor Against Darwinism has been read and thoroughly digested. I apologize for the dreadful length of this piece, but someone needs to quote what Darwin actually wrote about selection - placing Fodor's false "dilemma" into context within the history of evolutionary biology - and unmuddling the many misunderstandings that Fodor has concerning biology and genetics.
Fodor: "It is, in short, one thing to wonder whether evolution happens; it's quite another thing to wonder whether adaptation is the mechanism by which evolution happens"
Fodor commits equivocation with the word "evolution" by cashing-out its "mechanism" as "adaptation is the mechanism by which evolution happens". To Darwin, "evolution happens" - because natural selection and sexual selection among sexually reproducing organisms drive differential survival and reproductive outcomes. An "adaptation", as an adaptive trait, is a consequence of evolution. The process of "adaptation" is how effectively living organisms survive and reproduce within their habitats. In neither sense of the word "adaptation" is it the "mechanism" of evolution. The term "adaptation" is not (nor has it ever been) used to describe "the mechanism by which evolution happens".
Darwin advanced his theory to explain how the variety of life arose from "common descent". Natural and sexual selection among sexually reproducing organisms are drivers of evolution. Under the theory of natural selection (NS), the environment preserves individual organisms on the basis of their carrying traits which confer survival advantages on them. Conversely, the environment eliminates individual organisms on the basis of their carrying traits which confer survival disadvantages on them. Under the theory of sexual selection (SS), (1) in some species, males compete for access to the females and (2) in other species, females select attractive reproductive traits, displayed by the males. Mating between the selecting and the selected individuals leads to non-random, differential reproductive outcomes. This results in genetic novelty and in more raw material on which NS operates.
Fodor: "This is what Darwin does; he introduces the intensional context `select for...'. By stipulation, one but not the other of two coextensive traits can be selected for in an evolutionary process."
Fodor: "In practice, this comes down to claiming either that there are laws of selection, or that selection involves intervention by a mind (an agent)."
Fodor: "since Darwinism, or anyhow adaptationism, is itself committed to intensionally individuated processes like `selection for'."
Contra Fodor, Darwin introduced no such spooky phrase to describe selection. A strawman is being made out of Darwinism by attributing the verb "select for" to Darwin, distorting Darwin's take on NS then criticizing "Darwinism" with the distortions made to it. By slapping the phrase "select for" "one but not the other of two coextensive traits" onto what is imagined that Darwin wrote about NS is pure Fodorism - not Darwinism.
The morning star and the evening star are coextensive. They have the same reference (the planet Venus), but are different senses of it. A person - who has no knowledge of astronomy - can cognitively dissent that the morning star and the evening star are the same object. A neutral trait can piggyback on an adaptive trait within an organism, but - if the object of selection is an individual organism, a unique, selectable organism cannot piggyback on a unique, non-selectable (neutral) organism. Since organism A (a selectable creature) and organism B (a neutral, non-selectable creature) do not have the same reference - trivially, Fodor's Fregean gambit to intensionalize NS crumbles into dust.
Fodor: "there's a usage according to which organisms (or their phenotypes) are what get selected, but what they gets selected for are some or other of their traits (or `properties'). It's perfectly ok to talk that way, so long as you bear in mind that traits are themselves individuated intentionally. Distinct traits can have the very same extensions; that is, they may be distinct traits of the very same organisms."
The usage "according to which organisms" are what get selected by the environment is Darwin's. Again, he does not use the verb "select for" anywhere in the Origin. Assume - per impossible - that Fodor's spin on the verb "select for" is coherent. If NS "selects for" viable individuals (not for "intensionally individuated" traits), then Fodor's "dilemma" (which mentalizes selection as "selection for" "one but not the other of two coextensive traits" Fregean-style) dissolves.
What the object of NS is: the individual, the gene, the trait, the group or the species had been controversial to evolutionary biology. However, it's obvious that Darwin's primary object of selection was the individual organism. To Darwin, NS does not select (or 'select for') traits. It resultantly selects an entire individual, carrying a diverse bundle of survival, reproductive, neutral and disadvantageous traits. In the passages below, Darwin's "variations", "each organic being" and "individuals" refer to individual organisms - not traits.
Darwin: "every slight modification, which in the course of ages chanced to arise, and which in any way favoured the individuals of any of the species, by better adapting them to their altered conditions, would tend to be preserved; and natural selection would thus have free scope for the work of improvement." - The Origin of Species
Darwin: "It may metaphorically be said that natural selection is daily and hourly scrutinising, throughout the world, the slightest variations; rejecting those that are bad, preserving and adding up all that are good; silently and insensibly working, whenever and wherever opportunity offers, at the improvement of each organic being in relation to its organic and inorganic conditions of life." - The Origin of Species
Darwin: "As many more individuals of each species are born than can possibly survive; and as, consequently, there is a frequently recurring struggle for existence, it follows that any being, if it vary however slightly in any manner profitable to itself, under the complex and sometimes varying conditions of life, will have a better chance of surviving, and thus be naturally selected." - The Origin of Species
Keep this in mind: Darwin: "any being, if it vary however slightly in any manner profitable to itself, under the complex and sometimes varying conditions of life, will have a better chance of surviving, and thus be naturally selected." (Darwin's individual vs. Fodor's trait as the primary object of selection)
Fodor: "But there is a serious problem about `free riding': cases where a trait that is NOT connected to fitness goes to fixation because it is (locally or otherwise) linked to a trait that IS connected to fitness. (This is the arch/spandrel situation)."
Darwin: "The preservation of favourable variations and the rejection of injurious variations, I call Natural Selection, or Survival of the Fittest. Variations neither useful nor injurious would not be affected by natural selection and would be left a fluctuating element, as perhaps we see in the species called polymorphic." - The Origin of Species
Keep this in mind: Darwin: "Variations neither useful nor injurious [neutral organisms with no mention of neutral traits, i.e. `free riding' spandrels] would not be affected by natural selection".
To Darwin, NS passes over neutral variations. Neutral variations are invisible to selection. One neutral organism cannot be coextensive (having the same reference but a different sense) with a distinct "useful" organism. In the sentence above, Darwin is referring to neutral individuals as "Variations" - not to neutral traits. Once again, Darwin proposed no such driver which "selects for" "one but not the other of two coextensive [useful and neutral] traits".
Fodor: "The Darwinian principle is that phenotypic traits are selected for their (presumably causal) connection with fitness."
Fodor: "Prima facie, this principle is falsified by phenotypic traits that go to fixation but are not connected to fitness (drift and the like)"
There's no such "Darwinian principle". Under Darwinian NS, individuals (as a whole) on the basis of their carrying clusters of many traits (not the traits themselves) are selected by the environment. Again, neither neutral traits nor neutral organisms are visible to NS. Neutral traits confer neither survival nor reproductive advantages or disadvantages on an organism.
Even if the object of selection were the trait - since the environment is blind to a neutral trait, it could not select between it and an adaptive trait. Continuing the Fregean analogy - if I had evening-blindness, I could not see the evening star - much less distinguish between it and the morning star.
Contra Fodor, a variant of a gene (an allele not a trait) is what goes into "fixation" via selection or chance - when it's carried by all of the individuals who reproduce within a population.
In 1929, Sewall Wright identified the process of drift. A neutral - invisible to selection allele - which may (or may not) "go to fixation" does so by chance (a copy error in a gene, a catastrophic event which decimates a population, etc.). The existence of the process of drift in nature no more falsifies NS - than does the existence of SS. [1]
Evolutionary theory is a theory - which accounts for the level of genetic variation and diversity, observed in nature. It's comprised of the following drivers and laws: the driver of NS explains the preservation of "utilitarian" traits - which organisms carry. The driver of SS explains (among other facts of nature) the persistence of "non-utiltarian" (disadvantageous to survival) sex traits - which principally males show. Mendel's laws of inheritance explain heredity. Genetic drift explains the neutral traits - which organisms carry. Should this theory fail to depict the multiplicity of genetic variation and diversity detected in nature then it would be falsified.
Individuals carrying many different traits adapt to their own environments. Traits do not go about - all by themselves and without phenotypes - adjusting to environmental conditions and reproducing. Only individual organisms do that.
Mayr: "For Darwin and most evolutionists since 1859 the individual organism was the principal object of selection. The individual is the entity which survives or not, which reproduces or not, and which reproduces successfully or not." - The Objects of Selection - http://www.pnas.org/content/94/6/2091.full
Before the publication of the The Origin of Species, Darwin noticed that evolution was problematic with natural selection (NS) as its near-exclusive driver. In the Origin, he briefly touched on aspects of SS. One of his articulated reasons for writing The Descent of Man, and Selection in Relation to Sex was to correct what he saw was a fatal deficiency in the theory. [2]
Without SS as part of evolutionary theory, what exists in nature is under-explained by it. Genetic diversity cannot be accounted for by NS alone. Darwin declared outright that the "bright plumage of male birds", birdsong, massive antler racks on deer and elk, "odoriferous glands" in male insects, many other "male ornaments", and the sizes, colors and structural differences between males and females could not have arisen solely by NS.
To Darwin and his descendants, the above "exaggerated male traits" do not convey obvious survival advantages. For example, such traits make their possessors very conspicuous to predators.
If "`free riding'", i.e. neutral traits piggybacking on adaptive traits poses "a serious problem" to evolution, then how (to Fodor) could the survival disadvantages conferred by "exaggerated male traits" arising from SS not deal a fatal blow to it? There are sexually selectable traits in organisms that are "connected to" downright survival unfitness - yet they are preserved. However, neither of these consequences of evolution poses any problem to evolutionary theory.
NS cannot explain the appearance and preservation of "male ornaments" in nature - because they do not convey obvious survival advantages on male's carrying them, but SS does explain them - because they do convey reproductive advantages on males.
Darwin: "Nevertheless, natural selection will determine that such characters shall not be acquired by the victorious males, if they would be highly injurious, either by expending too much of their vital powers, or by exposing them to any great danger. The development, however, of certain structures - of the horns, for instance, in certain stags - has been carried to a wonderful extreme; and in some cases to an extreme which, as far as the general conditions of life are concerned, must be slightly injurious to the male. From this fact we learn that the advantages which favoured males derive from conquering other males in battle or courtship, and thus leaving a numerous progeny, are in the long run greater than those derived from rather more perfect adaptation to their conditions of life." - The Descent of Man [3]
In fact - if evolutionary theory could not explain the traits detected in organisms - which are connected to survival unfitness and neutrality, then evolutionary theory would veer into crisis. It would radically fail to account for what is routinely observed in nature, experiments and the fossil record.
Fodor: "If there is an ecological arrangement in which large tails are fitness enhancing (in peacocks), then there is an ecological niche for large-tailed peacocks. But, on second thought, no. :`Is an ecological niche for...' is intensional in exactly the same way, and for exactly the same reasons as `is selected for...': from the fact that large tailed peacocks predominate in a population, it doesn't follow that large tailedness was selected for in peacocks, or that there is or ever was an ecological niche for large tailed peacocks."
For over 140 years, the existence of male ornaments (which do not confer survival advantages) - such as the "bright plumage" of the peacock's tail - has been explained by SS. The long tail, displayed by peacocks, is selected as a reproductive trait by peahens! Appealing to "fitness" in "an ecological arrangement" to account for the peacock's tail then intensionalising how it could not have come about as 'an ecological niche for' to prove that evolutionary theory is defective is positively blinkered. Perhaps, Fodor should have the base-line level of intellectual humility to yield to experimental evidence?
Darwin conducted the first SS experiment by surgically blinding a control group of peahens. The experimental (non-blinded) peahens, Darwin observed, showed a "preference" for mating with the "more ornamented" cock. He - also - observed that the controls could not, after blinding, "choose" peacocks on the basis of the cocks' tails showing a "bright plumage" - due to their inability to receive visual stimuli.
Darwin: "The females are most excited by, or prefer pairing with, the more ornamented males, or those which are the best songsters, or play the best antics; but it is obviously probable that they would at the same time prefer the more vigorous and lively males, and this has in some cases been confirmed by actual observation." - The Descent of Man
For the sake of argument, I'll play along with Fodor's "ghost in the machining" of evo-bio - by applying it to SS. Evolutionary Epistemologists speculate that uni-cellular organisms interacting in their environments marks the emergence of what they call the "quality of mind". Under this assumption - suppose it could be said that sexually reproducing, non-human organisms (peahens) select for "one but not the other of two coextensive [reproductive and neutral] traits" in a mate. For example, the peacock's brightly colored tail is a reproductive trait and the noise the peacock's tail makes in the breeze is - arguably - a neutral trait. Under SS, Fodor's "dilemma" could not arise - since a female's "mind" did the "selecting for" the reproductive trait - rather than the neutral one. Once again however - according to Darwin, organisms (mostly females) do not select for "one but not the other of two coextensive [reproductive and neutral] traits" in a mate. During the mating season, they select individual mates based on sets of secondary sex traits, displayed by potential breeding partners of the opposite sex. "exaggerated male traits" are indicators of male genetic/reproductive fitness. In a population, the genes of the "more ornamented" males proliferate at a higher rate - than do the genes of males who are less ornamented. SS theory has been confirmed over the course of decades and decades in experiments - where it counts.
Fodor: "Historical addendum: I suspect that Darwin got into this mess because he assumed that natural selection can be modeled by artificial selection: Start with breeding, take the breeder away, and you have natural selection. If so, then he was the victim of a fallacy of subtraction. That could happen to anybody."
The only "mess" Darwin got himself into was being born too early in the 19th century. He had no knowledge of genetics. Darwin's writing in both the Origin and the Descent was Victorian, somewhat amateurish and replete with allegory. He was attempting to introduce the theory of evolution to an audience which was either ignorant of or down-right hostile to evolution, so he used analogies - such as the breeder to help explain NS.
Take Darwin's "breeder" analogy away from NS, and one winds up with the environment selecting resultantly viable organisms, containing survival, reproductive, neutral and disadvantageous traits - rather than resultantly non-viable ones.
Fodor: "This is what Darwin does; he introduces the intensional context `select for...'. By stipulation, one but not the other of two coextensive traits can be selected for in an evolutionary process."
Fodor: "I don't mind people ignoring this argument; that's gone on for some 150 years."
I defy Fodor to bring up the link to the Origin of Species and search for the "mentalistic" phrase "select for" in the Origin. It does not appear anywhere in that 150 year old work. http://www.literature.org/authors/darwin-charles/the-origin-of-species.
Fodor: "A reasonable biologist might be willing to live without a selectionist evolutionary psychology so long as here's no implied threat to adaptationism per se. When the weather gets rough, there's an understandable temptation to lighten ship by throwing the psychologists overboard."
Throwing EP ("the adaptationist programme", i.e. that all of the psychological traits which humans carry conferred survival or reproductive advantages on their Pleistocene ancestors) overboard does not involve wailing and the gnashing of teeth. However, throwing Darwin (and evolutionary biology) into the same boat with EP, then proceeding to sink it with Fodor's "select for" "one but not the other of two coextensive traits" depth charge is something no biologist could put up with. To allow Fodor to equivocate NS away into "select for" "one but not the other of two coextensive traits" would be an act of suicide bombing. Turning on another rotten metaphor: we might exorcize the EP ghost, but Darwin will continue to haunt the bio-lab.
Fodor: "This appears to be a dilemma; one from which, as far as I can tell. Darwin has no exit."
Before twisting, torturing and wrenching evolutionary theory into what it is not, I encourage philosophers to read the core, experimental research in evolutionary biology. Scientifically, this theory belongs to evolutionary biologists. Just as with physicists and the theory of General Relativity, biologists have the final say over whether evolutionary theory is viable (or not).
End Notes: In the 1930s - during the Modern Synthesis - which formally fused Darwin's evo-drivers and Mendel's laws, the "select for" verb was introduced. However, the phrase used was: "select for the phenotype" - not "select for" "one but not the other of two coextensive [adaptive and neutral] traits". A phenotype is "all of the characteristics of an individual organism that is visible to the environment, which can be selected for or selected against". Had the Synthesizers (Fisher, Wright, Dobzhansky, Haldane, Mayr, etc.) suspected that this poor verb would be deformed then launched to shoot an intensionalist torpedo into the evolutionary works, they would not have employed it. The usage of the phrase: "select for the phenotype" does not metaphysically, inferentially or otherwise commit the Synthesizers to an intensionalised interpretation of NS.
Mayr: "Darwin was a holist: for him the object, or target, of selection was primarily the individual as a whole. The geneticists, almost from 1900 on, in a rather reductionist spirit preferred to consider the gene the target of evolution. In the past 25 years, however, they have largely returned to the Darwinian view that the individual is the principal target."
Fisher ("the fundamental theorem of natural selection"): "The rate of increase in fitness of any organism at any time is equal to its genetic variance in fitness at that time." - The Genetical Theory of Natural Selection - https://archive.org/details/geneticaltheoryo031631mbp
Irwin: "Natural selection is evolution that occurs because individuals with some traits survive and reproduce better than do individuals with other traits. As a result, those traits that result in high survival and reproduction are passed from generation to generation, through reproduction, at a higher rate than are other traits. These traits become increasingly more and more common in populations."
Fodor (contradictorily): "In fact, strictly speaking, traits don't get selected at all; traits don't either win competitions or loose them. What wins or looses competitions are the creatures that have the traits. That's to say that what's selected is whole phenotypes; and, quite possibly, whether a trait is fitness-enhancing depends a lot on what phenotype it's embedded in."
Eureka! Darwin got it right - i.e. Fodor equals malodor!
(1) Evolutionary Rate at the Molecular Level
"Finally, if my chief conclusion is correct, and if the neutral or nearly neutral mutation is being produced in each generation at a much higher rate than has been considered before, then we must recognize the great importance of genetic drift due to finite population number in forming the genetic structure of biological populations. The significance of random gentic drift has been deprecated during the last decade. This attitude has been influenced by opinion that almost no mutations are neutral, and also that the number of individuals forming a species is usually large that random sampling of gametes should be negligible in determining the course of evolution, except possibly through the "founder principle". To emphasize the founder principle but deny the importance of random genetic drift is, in my opinion, rather similar to assuming a great flood to explain the formation of deep valleys but rejecting a gradual but long lasting process of erosion by water as insufficient to produce such a result." -- Motoo Kimura (1967)
(2) However in "The Variation of Animals and Plants Under Domestication" (1868), Darwin, also, suggested "pangenesis" as a potential driver of evolution (over the short-term). According to the theory, beneficial traits acquired during the lifetime of an organism are passed onto offspring, and particles called "gemmules" shed by body cells could become localized in the reproductive organs; Thus - to Darwin, evolution could be pushed for a short span of time, a few generations by pangenesis.
"The modifications acquired through Sexual Selection are often so strongly pronounced that the two sexes have frequently been ranked as distinct species, or even as distinct genera. Such strongly-marked differences must be in some manner highly important; and we know that they have been acquired in some instances at the cost not only of inconvenience, but of exposure to actual danger." -- Darwin (1871)