Interest-dependent functions of the sort we began with are not good objects for scientific investigation. However, there are other notions of function that seem to involve interests in a way that makes them more reasonable candidates for scientific study. They are found in the biological sciences.
Evolutionary scientists speak of
adaptations
, where an adaptation is a feature of a group of organisms – a feature such as an organ like the vertebrate eye – that is claimed to have the shape and complex structure that it does as the result of evolutionary processes, and that has its current transmissible form in the species, it is claimed,
because
it enhances the reproductive capacity of the
creatures that have it.
4
Typically, one finds the assumption that reproductive success comes from some
transmissible mutation serving some specific role in an organism's operations that is assumed to aid the viability of a species – in that sense, the species’ interests. At the least, it performs a function for an organism that enhances its ability to
procreate. Pinker and Bloom (
1990
), for example, read in this way what they suppose is increasing communicative success of adaptations they claim appear in the
evolution of language, and they believe that they can explain the ‘shape’ of natural language in this way. It is not at all obvious what evidence they have for their suppositions, or for those advanced by
Pinker and Jackendoff (
2005
) in their critique of Hauser,
Chomsky, and Fitch (
2002
). All these appear on the face of it to be ‘just-so’ stories of the sort that
Richard Lewontin sharply criticized in his (
1998
). However, it is not too difficult to find plausible examples with other organs – the eyes and the visual system, the ears and the auditory system, for example – cases that appear to be plausible because there is accumulated evidence (comparative, whether involving analogies or homologies) of improved viability of a species – although where such evidence is found, it is entangled with other factors, including contributions best understood only by appealing to non-biological sciences such as physics. In those cases where there
is
clear
evidence of adaptation for survival, evidence gathered by investigating the evolutionary path of a species compared to others, one can speak of specific subsystems of an organism that serve a function in something a bit like the interest-dependent-function sense, although generalized to amount to something like “survivability for species x.” For it is assumed that the shape and structure one encounters in a species’ ‘adaptive’ system are what they are because they serve the reproductive interests (in some broad sense) that they are claimed to for the creatures that have them – that the selectional advantages of having such a structure explain (in the relevant sense) its evolution and
current state. Vrba and Gould, for example, once suggested that use of the term “function” (in the evolutionary biological sense) be restricted to cases where there is some evidence of evolutionary ‘shaping.’ There is some danger in speaking of interest in this domain, for the evolutionary biologist does not – or should not – allow the notion of an
agent
's interests to play a role in science, and it can be difficult to disentangle that notion from one that is part of the explanatory toolbox of a field of scientific research. If the notion of interest enters at all, it should be a carefully defined notion, isolated from commonsense notions of agents and their projects and intentions in carrying out actions.
There are very significant challenges to the scope and validity of at least some adaptationist claims within biology itself.
Darwin himself expressed doubts about the explanatory reach of selectional adaptation; the last sentence of the introduction of the third edition of
The Origin of Species
reads, “I am convinced that Natural Selection has been the main
but not exclusive
means of modification” (emphasis added). He was right to be cautious, as current understanding of ‘channeling’ of growth in ‘evo-devo’ (evolution-development) has abundantly shown.
Wallace at Darwin's time pointed out that it is very unlikely that selection could explain the introduction of the capacity we humans alone have to do mathematics. That natural selection does not deal with everything in the way of explaining ‘shape’ and biological form – and perhaps deals with very little – was emphasized by
D'Arcy
Thompson in the early 1900s and Alan Turing in the mid-1900s. They pointed to a significant role for physiochemical explanation in dealing with structure and modification and emphasized that formal functions could explain form and its permissible variations in a way that brought into question the value of adaptationist and selectional explanations. Further,
Waddington and more recent proponents of the developing field of
evo-devo have pointed out that not all organic structure can be scientifically explained in this way, and perhaps very little. For one thing, there is the fact that modification requires
mutation, and mutation can only proceed within the constraints set by physics and chemistry, among other sciences: possible structures and modifications of structure are limited by the laws of nature. Various structural features of organisms, for example, cannot be explained by genetic instruction sets alone, nor can the way
phenotypical development takes place; ‘epigenetic’ factors play a crucial role in the latter. Scaling of skeletal structure (the genome cannot be thought to provide a complete specification of the sizes of each bone in a specific organism) and symmetry (the fact that each rib on the right has a homologue on the left, each wing of a butterfly the same pattern as the other . . .) are two examples. And there are issues that bear on structure and form that selectional adaptation does not speak to in any significant way: the fact, for example, that what have been called “control” or “master” genes are found in the same form in a large number of different species that cross biological clades.
Walter Gehring has long pointed out that vision in all species in different clades must be linked to the fact that all species have homologous control genes – PAX-6, in the case of vision. This suggests that
vision did not evolve separately in (say) fish, insects, and vertebrates, but that it is available to all creatures with PAX-6 (and other genes involved in introducing rhodopsin and putting its sensitivity to photons to use through various mechanisms), with variation depending on the rest of the structure of the organism, plus background conditions. Similar points can be made for other ‘organs’ and their distributions in species of organism.
As for the
soundness of selectional adaptationist claims, several have pointed out that evidence is too often question-begging (just-so stories), or does not exist and cannot be found, making an adaptationist claim empty.
Focusing on cognitive systems, Richard Lewontin (
1998
) raised serious doubts about the evidence claimed for selection of several cognitive capacities, including some that seem to be unique to humans, such as language. At the end of the article, he remarks in response to the volume's editors’ suggestion that he soften his criticism, “We should reserve the term ‘hypothesis’ for assertions that can be tested.” And at the very end of his remarks, he emphasizes his main point, that history provides virtually no
evidence for change and adaptation in cognitive capacities. One of Lewontin's primary targets was
Pinker and Bloom's view that selection alone can explain the introduction of a “complex system” such as language. His criticism of Pinker and Bloom resurfaces in modified and more precise form in
Hauser, Chomsky and Fitch (henceforth HCF) (
2002
). Some of the main points of the HCF article are raised elsewhere in this volume. HCF point out that while we might find at least some evidence for selectional adaptation of aspects of language that are outside the core in what HCF call “FLB” (for “faculty of language, broad”) as opposed to
FLN (“faculty of language, narrow”), claims about the adaptive evolution of the core computational system of language FLN with its recursive character and capacity to link sounds and meanings over an infinite range have nothing to back them up. For discussion, see HCF (
2002
) and critical response from
Pinker and Jackendoff (
2005
) followed in the same volume by
Fitch, Hauser, and Chomsky's (
2005
) and Jackendoff and Pinker's further effort (
2005
). On the relevance of the Minimalist Program to this discussion, see the online Chomsky, Hauser, and Fitch (
2004
), available on Hauser's website. See also the discussion in the main text, and especially Chomsky's remarks on
perfection and design in our 2009 discussion (pp. 50ff.).
Discussions of function, adaptation, and evolution are complicated by the fact that it is not clear what ought to figure in
evolutionary theory. Is Turing's work on morphogenesis (which he thought is best located in chemistry or physics) in or out? What about
Gould and Lewontin's spandrels? Should one admit
Chomsky's saltational view (explained below) of how language came to be introduced into “evolutionary theory”? These decisions can be left to those working in the field, as can the explanatory status of natural selection. Nevertheless, there is good reason to believe that the claim that adaptationist accounts can explain everything in the way of biological structure, development, evolution, and speciation is at an end – supposing, of course, that responsible scientists actually believed that they did in the first place.
While we can leave the issue of the precise explanatory status of selection, adaptation, and adaptive function to biologists, there is a simplistic view of
selection and evolution that needs no expertise to reject out of hand. Perhaps
in an effort to popularize evolutionary theory and/or present to lay audiences a readily-understood alternative to a theological explanation of why biological species are the way they are, some have exploited a connection between evolution and commonsense understanding's apparently
default view of learning, a view found in behaviorism's and empiricism's view that we learn by coming to respond to input in the ‘right’ way by being trained to form the ‘right’ dispositions to respond. We shape our responses to the environment by having the ‘right’ responses rewarded, and the ‘wrong’ ones punished. Relying on this picture, many have treated evolution as an historicized version of learning so conceived: we and other creatures are the ways we are because each species has adapted in its structure and development to have an optimal strategy for its ecological niche;
Skinner himself supposed this, revealing how little he understood of what evolution involves. Exploiting a connection to this view of learning is misguided strategy; one ends up defending something for which there is no warrant except that it appears to be all-encompassing. There is no modesty to this view – no recognition that selection's role is limited, if even that. Nothing is said about how evolution and phenotype development and growth must take place within the constraints set by physics, chemistry, biology, perhaps some form of information theory. There is no mention of the fact that many genes are conserved over species and clades. Epigenetic factors are ignored. ‘Happy accidents’ of the sort found in what
Lewontin and Gould called “spandrels” are not mentioned. Too often – especially in the cognitive domain – there is only a minimal effort to find evidence for claims: just-so stories are common. Virtually all features within a species and their structures and behaviors are treated as though they were ‘selected’ over a long period, chosen by virtue of adapting to the environment in which a species is found. While there are gestures toward a role for the genome, nothing is said about its precise structure and how it works and one finds no mention of epigenetic factors. The genome's role on this
naïve view of evolution – one too often popularized by those who should know better – is just to transmit from generation to generation successful ways for a species and its members to ‘solve problems’ in dealing with an environment. There is little or no disentangling of the notion of the interests and actions of agents from the ‘interests’ and ‘actions’ of genes. Compounding the error, genes are often presented as having some direct control over an organism's behavior, rather than providing an organism with various systems that it can use to deal with its environment, and – certainly in the case of humans – do a great deal more too. Like ‘learning’ for the behaviorist, the naïve but very popular view of ‘selection’ comes to be treated as an explanation of virtually every trait of an organism. And this kind of naïve simplification comes to assume the trappings of a metaphysical principle. Rather than God, one finds appeals to evolution (so conceived) alone as the explanation of why we are the way we
are and act in the ways we do. Confusion and ideology are served, not clarity and reason – nor science.
Rejecting this notion of selection is not, of course, rejecting the explanatory power and scope of evolution, properly understood. But as indicated, it is not exactly clear what is to be included in the theory of
evolution.
With that caveat in place, and leaving aside the to-be-determined final status of the
explanatory reach of adaptation and adaptive function in evolutionary theory, it is time to acknowledge that biology does seem to provide a place for functional explanation that several centuries of scientific research have convincingly excluded from most forms of physical science. By way of background,
Ernst Mayr (
2004
) argues against reducing biological explanation to physical because, he suggests, biological theories are committed to speaking of function where physical theories are not. It is not clear what Mayr has in mind by the physical, nor – in a related vein – by biology offering an ‘autonomous’ mode of explanation. Granted, biology is not physics, but it – like linguistics, if Chomsky is right – is a naturalistic and thus in an important sense physical science. Ignoring, however, the issue of what is or is not physical, and focusing on the most plausible kinds of cases where functional explanation makes good contributions, let us look at a “system-within-an-organism” or “organ-within-an-organism” notion of function. It may not be quite what Mayr had in mind, but it looks reasonably close to it.
An “organ-within-an-organism” notion of function is interesting for our purposes for two reasons. One is that it allows for clearly stated and falsifiable hypotheses, unlike far too many claims made in dealing with issues of function in biology. And second, on the face of it, it suits
Chomsky's conception of a computational theory of language, where language is thought of as an ‘organ’ – which is how Chomsky construes the language faculty – or at least, how he conceives its computational core and its specified ‘contributions’ to other mental systems. ‘Doing a specific job’ (fulfilling a function within the organism
by
interacting with specific other systems in specific ways over interfaces) seems to be built into the idea that a computational theory of language is a formal science of a system that “interfaces” with other systems by providing them information that they can use, and apparently even doing so in an optimal way, so that the design of the language faculty can be conceived as perfect – or at least, a lot closer to perfection than was thought not long ago. Language – using Chomsky's informal term – “instructs” production/perception and conceptual/intentional systems and, in order to do so, must provide them with ‘instructions’ (relevant forms of information) that they can ‘use’ or put to use – that is, come into operation in the way(s)
characteristic of the relevant system(s). Note that ‘use’ here is not “use by creature” or “use by organism as a whole,” and especially not “use by agent.” It is “employment by other (designated) systems in specific ways,” which is what places this notion of function in the ranks of empirical investigation.
Plausibly, in fact, we could entirely abandon the term “function” in dealing with specific system-internal system transactions and thereby avoid the obscurity that this term seems to invite. That is probably the wisest strategy – but not one, apparently, that people are fully willing to adopt. It is not clear why, although I suspect one factor is that its use in what appears to be a reasonably well understood context attracts attention. A possible parallel is found in the following case, and numerous others. A recent article in the
Proceedings of the National Academy of Sciences
uses words such as
choose
and
move
in speaking of the entirely chemical responses to environmental food sources for
slime molds. The cost is confusion, but the reward is attention to an ‘amazing’ discovery.
So ignoring the
matter of whether biology is “autonomous” in the way Mayr seems to think, and focusing on reasonably well-specified cases in sciences that deal with specific ‘organs’ (or at least their ‘cores’), and ignoring too the advice of the paragraph above, it might make no sense to speak of a biological ‘organ’ of this sort
without
introducing the relevant notion of a function – of what the organ ‘does’ for and with the systems with which it interacts. And if Chomsky accepts such a notion of function and – as indicated – this notion of function is not thought of in terms of adaptations to an environment, nor in terms of what an organism ‘does’ with what a system provides, one can make a plausible case for the language system serving a biological function in something at least reasonably close to what Mayr may have had in mind.
It is not altogether obvious, however, that Chomsky does accept this as an autonomous notion of biological function. Some reasons for doubt appear in the discussion of the skeleton example in the main text (see also Lewontin
2001
); not only are there many plausible claims about
functions for the skeleton (which is also an ‘organ’ of sorts in the body interacting with immune, circulatory, motor . . . systems), but some descriptions of its functions look very informal (giving structure to the body), with little prospect for making them precise within a naturalistic theory. Others appear in our 2009 discussions of the
design and perfection of the language faculty on pp. 50–55. Likely the most significant of all appears two paragraphs above: for the relevant scientific purposes in question, why not abandon the term “function” entirely and instead speak in a well-understood way of an organ's ‘interfaces’? Ignoring all this, however, there is a case to the effect that Chomsky does acknowledge some notion of inter-organic function (cf.
Epstein
2007
).