A concise discussion of Darwin's Problem

A bunch of the good guys (Bolhuis, Tattersall, Chomsky and Berwick (BTCB) have a new paper out in Plos Biology that reviews in a concise manner the logic relating the Minimalist Program (MP) and Darwin’s problem (DP). The paper is worth knowing about for several reasons, not the least being that it came out in Plos Biology, an important venue for bio research. It also is a nice short paper that one can give to friends (I in fact just sent it to an econ buddy of mine) if they are curious about what kinds of BIG issues linguists are trying to address.

For the cognoscenti, the discussion will be quite familiar (though if you are like me and love greatest hits albums, this will be a pleasure to read). It starts where all good evo discussions have to start; with a characterization of the faculty whose emergence one is interested in explaining). BTCB hits all the required notes: language is not speech, nor an instrument for communication. Or, more precisely, externalization is not relevant to the key features the “language faculty per se” (1).  Rather (and get ready for the surprise), “language is a computational cognitive mechanism that has hierarchical syntactic structure at its core…” (1). In other words, the target of evo explanation in the domain of language is how this generative capacity came to be fixed as a biological property of humans. [1]

With the target of explanation specified, BTCB goes on to make the observation that MP has the properties required to allow an assault on this problem. What the paper does not say (but I think is important), is that prior to the emergence of MP linguists had little to contribute (or more accurately, little they could contribute) to the question of how FL evolved. How does MP advance the evo issues? By providing “an extremely simple” account of human syntax, “simple” being the key feature.  In other words, what MP affords (or, at least, promises) is a characterization of syntax as comprising a single simple combinatoric operation, which, when combined with the “general cognitive requirement for computationally minimal or efficient search,” “suffices to account for much of human language syntax” (p. 1-2).  In other words, what MP does is so simplify the structure of FL that it makes it possible to understand how an FL with these characteristics might have come into being. Or, to put this another way, prior to MP the understood structure of FL was so complex and sui generis (had so many moving and interacting parts) that it was impossible to see how it could have evolved.  In short, the only hope we have of providing an account of how FL arose in the species is if FL has an MPish structure. Note, that this is very much a conceptual argument. Evo details, as BTCB notes, will be very hard to come by, as they note and we return to anon.

BTCB proceeds to observe two nice features (consequences?) of a simple FL: (i) it could have emerged all at once, and (ii) it would have remained stable given its lack of moving parts. As BTCB note, there is evidence that both these features are correct.

The second (viz. that FL has remained largely unchanged since its emergence) is almost certainly correct as “there is no doubt that a normal child from England raised in northern Alaska would readily learn Eskimo-Aleut, or vice versa” (p. 2). In other words, so far as we can tell all humans (even those from isolated communities) share a common FL as witnessed by the fact that any human can learn any language if properly environmentally situated. As BTCB notes, the uniformity and stability of FL “points to the absence of major evolutionary change since the emergence of the language faculty” (2). It also, IMO, supports the idea that FL is not itself the end-product of selection for if it were we might expect to see continuing differential changes in FL’s structure, with different groups having slightly different FLs facilitating the use and acquisition of some languages at the expense of others. We, apparently, do not see this, which suggests that all FLs are of a piece, which would make sense if they were very simple in an MPish sort of way.

Let’s now turn to the issue of rapid emergence. Finding evidence relevant to making evo claims turns out to be very (very very very…) difficult, with the available evidence being “quite indirect.” BTCB reiterates a point made by Lewontin long ago (here) that getting non-trivial evidence that bears on the issues is not at all easy. In fact, BTCB identifies exactly one kind of useful type of evidence for dating the emergence of “language,” and it comes from archeology. The evidence is the sudden widespread explosion of symbolic artifacts in the archeological record roughly 100 thousand years ago. These artifacts have been used as “proxies” for language, the idea being that the emergence of language (and the cultural evolution it supports?) is the main causal factor behind this sudden rise in symbolic artifacts. This, BTCB emphasizes is “quite indirect” evidence for the presence of a fully operational FL, but it is all we’ve really got given the exigencies of finding the standard kinds of relevant evidence commonly used to advance reasonable evo hypothesizing (again, see Lewontin on this for an elaborate and useful review). This archeological evidence (which I assume that Tattersall is responsible for reviewing here) points to a relatively rapid emergence of FL about 100kya (p. 3). The artifact-proxies for language emerge in the archeological record all at once, in many places and quickly. It suggests that whatever took place did not happen gradually (contra many standard Darwinian tropes). Note, the possibility of rapid emergence is conceivable if what made it possible is a simple addition to an otherwise available system, the kind of system MP aims to provide.

To wrap up: BTCB has two important virtues: (i) It illustrates the strong conceptual bond between MP and DP, and (ii) it illustrates how meager the actual data bearing on evo concerns in the domain of language really are. As a matter of facts we still know next to nothing about how FL emerged. Moreover, we are unlikely to learn anything in the near future about the details given how hard it will be to find relevant evidence bearing on the issue. Nonetheless, BTCB shows that some progress has been made, but mainly from the linguistic/conceptual side. I think that BTCB is right in thinking that MP is a conceptually important move forward, as any conceivable account of the mergence of FL will require something like MP. So if you are Darwin enchanted then you’d better become a card- carrying minimalist. It’s the only hope, even if it is a faint one.

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[1] The paper also makes some nice methodological observations concerning what an evolutionary account can and cannot hope to deliver. BTCB observe that as a matter of logic, evo accounts cannot deliver explanations of how what has evolved actually works.  This is why a grammatical characterization of FL is so vital. Evo accounts need specifications of mechanisms. Specifications of mechanism can proceed quite happily without evo accounts of how they got there.  For further discussion of this point, see the Bolhuis and Wynne paper referred to in the notes. It’s worth a read.