Book Club: Darwin’s Unfinished Symphony, 5, the evolution of language

Why is it that only the species Homo sapiens has evolved language? Well, aside, possibly, for other, now extinct, species of our own genus. Despite much talk of animal communication, that’s just what other species do: communicate. Language is a very special, and highly sophisticated, type of communication. Characterized by grammar, capable of recursivity, inherently open ended. Nothing like that exists anywhere else in the animal world. Why?

That’s the topic of the eight chapter of Kevin Laland’s Darwin’s Unfinished Symphony: How Culture Made the Human Mind, which we are in the midst of discussing. A major problem here, as Laland points out, is not that we have no idea of the possible answer, but rather that there are too many explanations on offer, none of which seems to quite do the job. Here is a partial list. Language evolved:

• To facilitate cooperative hunting.
• As a costly ornament allowing females to assess male quality.
• As a substitute for the grooming exhibited by other primate species.
• To promote pair bonding.
• To aid mother-child communication.
• To gossip about others.
• To expedite tool making.
• As a tool for thought.

And of course it’s very possible that language evolved to fulfill more than one, or even all of those functions! The stumbling block isn’t the imagination of researchers, but rather the dearth of relevant empirical evidence (something, of course, that isn’t the case only in some areas of evolutionary biology).

Part of the difficulty stems from the fact that the evolution of language was a singular event, which precludes the use of one of evolutionary biology’s standard tools of investigation, the comparative phylogenetic method. Moreover, languages don’t leave much of a fossil record, thus taking out a second major tool from the biologist’s box.

Kevin proceeds by listing six criteria (and adding a seventh of his own) that a successful theory of language’s origin should meet in order to be further considered (I refer the reader to the chapter itself for more in-depth explanations concerning each criterion):

1. The theory must account for the honesty of early language. (If words are easy and cost-free, why should anyone believe what others say?)
2. The theory should account for the cooperativeness of early language. (Why should people, early on, have gone out of their way to help others by passing to them valuable information?)
3. The theory should explain how language was adaptive from the onset. (As it is hard to imagine how it could have been a spandrel.)
4. The concepts proposed by the theory should be grounded in reality. (That is, how did words acquire meaning in the first place?)
5. The theory should explain the generality of language. (As opposed to the specificity characteristic of every other animal communication system.)
6. The theory should account for the uniqueness of human language. (Why us and not anyone else?)
7. The theory should explain why communication needed to be learned. (Why is it that language needed to be socially learned and capable of changing rapidly?)

Laland then concludes that no theory suggested so far meets all seven of these criteria, and I think he’s right. His preferred answer should, at this point in our discussion of the book, come as no surprise:

“[This] raises the question of why humans alone should exhibit a culture that ratchets up in complexity. Theoretical studies answer this question by showing that high-fidelity information transmission is necessary for cumulative culture, but then pose the supplementary question of how our ancestors achieved high-fidelity transmission. The obvious answer is through teaching.” (p. 183)

Kevin then proceeds in orderly fashion by comparing his preferred hypothesis — that language evolved in order to teach relatives — to the seven criteria just listed, finding that the language-to-teach scenario satisfies all of them.

At this point it will be good to step back for a second. To begin with, I’m sure that other students of the evolution of language will dispute both of Laland’s claims: (i) that no other hypothesis is a good fit for all seven criteria, and (ii) that only the language-to-teach hypothesis does a good job with the same criteria. Or perhaps (iii) someone will question the adequacy or necessity of one or more of the criteria in the first place.

For me, though, what makes this chapter the least convincing of those we have read so far is that even if we grant Kevin everything he is arguing for, we are still left, at best, with an hypothetical scenario that falls far short of empirical verification. Yes, maybe language evolved so that we could efficiently teach valuable information to our relatives, and things then went on from there. Or maybe there is a clever variant of one of the other hypotheses now on the table that will be even more convincing than the present analysis. Or perhaps there is yet another scenario that simply nobody has thought up yet. We just don’t know. And to be honest I don’t think we are likely to know any time soon, if ever. Precisely because of a major stumbling block acknowledged by Laland himself: the evolution of language was a unique historical event, and unique historical events are exceedingly difficult (though not impossible) to study.

While reading the chapter, I was reminded of some sharp, and I’m sure very much unwelcome words written by one of my scientific role models, the Harvard geneticist Richard Lewontin. In a book chapter entitled “The evolution of cognition: questions we will never answer,” he presents a critical analysis of the literature on the topic, making an argument that builds up to the following conclusion:

“I must say that the best lesson our readers can learn is to give up the childish notion that everything that is interesting about nature can be understood. History, and evolution is a form of history, [often] simply does not leave sufficient traces. … Form and even behavior may leave fossil remains, but forces like natural selection do not. It might be interesting to know how cognition (whatever that is) arose and spread and changed, but we cannot know. Tough luck.” (p. 130)

Seems to me that one could easily replace “cognition” with “language” and still be largely in the right. I’m sure Kevin will disagree, and I look forward to his comments.

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(Note to the reader: this commentary covers that major part of chapter 8, devoted to the question of the original function of language. The latter part of the chapter addresses a different, if related, question: how was it computationally possible for hominins to learn language, regardless of which selective pressured favored it? While interesting, I elected not to cover this bit, in order to focus discussion on what I think are the more crucial points of the chapter.)