Thursday, January 29, 2015

Let's talk tools

Craig Sailor sent me this link to a paper in Nature that argues for a correlation between the gradual emergence of a certain kind of stone tool and the emergence of language. As Caig put it in his note to me:

"They suggest a causal relationship: the skills required to create the tools in question are complex enough that verbal instruction was significantly more effective than imitation (which they support with experimental evidence), meaning the gene(s) responsible for communication were preferentially selected for in the environment, leading to the general evolution of language."

They actually contrast five kinds of "transmission" mechanisms. Goring form the least interactive to the most they consider (i) Reverse engineering (subject given stone and tries to figure out how it was made) (ii) imitation/emulation (subjects watches someone make the stone and tries to copy this), (iii) basic teaching (proficient maker guides learner but no physical interaction), (iv) gestural teaching (teacher molds gestures of learner on stone) and (v) verbal teaching (teacher instructs learner by talking).  The results of the experiment are that one finds better and better information transmission as one moves from  (i) through to (v). In other words, as regards EVOLANG concerns, providing instruction via talking really helps. The suggestion is that "tool making created a continuous selective gradient from observational learning to much more complex verbal teaching…the more complex communication allowed the stable and rapid transmission of increasingly complex technologies, which in turn generate selection for even more complex communication and cognition, and so forth (5)." As the authors note (there are 12 of them). Their results place "little necessary constraint on when teaching and language may have evolved…" though they wish to suggest that this evo pressure of the indicated cline started having some effect at least 2.5 mya. 

Some comments: It's pretty clear that the authors want to say something here about the evolution of our NL capacities (indeed, this is what made the results popular science newsworthy (see here)). However, so far as I can tell they do not isolate what specific linguistic features are required to juice the tool building transmission system. One can imagine a very limited "language" that would suffice (e.g. do this, like this, etc) to produce good tools and tool making instructions.  And if this suffices to get good tool making and good tool making teaching then it is unclear what explanatory mileage one can get form this experiment. Said another way, the "proto-language" gestured to above (which strikes me as quite possibly sufficient for the tool making purposes discussed) is a very far cry from Natural Languages. And though, I am willing to grant that the more complex the language structure (both wrt word meaning and the combinatorics) the more information one can transmit, and the greater the complexity of the transmittable information the more complex the teaching that it can support, I do not see how this explains the emergence of FLs with the characteristics found in NLs. Or, to put this more charitably, I do not see that languages with the two basic features that we have discussed (here and here) are necessary for making tools. Note that I have no trouble seeing how the emergence of more and more complex linguistic systems can support more and more sophisticated teaching, but that does not support the causal direction of interest. The causal direction needs to be from tools to language not from language to tools.

Let me note two points: First, that unlike much of what passes for EVOLANG this work aims to give an account of how linguistic capacity evolved. The idea is that it piggy backs on selective advantage of tool making. This is good: it's heart is in the right place. Unfortunately, second, the paper is actually a nice example of the failings of much of the EVOLANG literature that I have looked at in that it never actually specifies what it takes to be the necessary features of languages required for the task at hand. Would the capacity to form simple NVN strings suffice? Would words that adhered to RD suffice (btw, I can't see why not on both counts)? Do we need unbounded hierarchically recursive structures to get flint tool making off the ground?  Who knows?  The problem is not that the paper doesn't address this issue, but it doesn't even recognize its relevance.

Let me end by stating again what someone like me (and I suspect you too) want out of an EVOLANG account: how did our linguistic capacity arise? Which one is that? Well, for starters, where did the linguistic capacity with the two key features Chomsky discussed in the above linked to articles come from? Isolate the features of language without which tool creating transmission information is impossible.[1] That's a first step. The second is to show that the causality is from tools to language capacity, rather than the other way around. So, sure there is a correlation: more complex tools goes with more complex language, but more complex everything goes with more complex language. So big deal.

Let me say this another way: the paper, taken at face value, suggests that some kind of communication system would have been useful in making the flint tool discussed. However, as noted this does not imply that on had an NL like ours earlier than 75-50 kya. It only says that it would have been useful. But quite possibly (likely) a more limited  communication system with properties quite unlike those found in our NLs would have been just as useful for this task.  Nor is there any reason given why having such a more primitive system is a causal precondition for having ours. And therefore the relevance of the results completely escapes me. Here is yet another case where not describing the properties whose evolution you want to explain has led to a whole bunch of time intensive hard work being done with no obvious gain in insight. In sum, this looks like another case of those things not worth doing are not worth doing well.

[1] As an example of what I have in mind (i.e. pairing evo advantages with properties of the linguistic system) see here. Please excuse the self promotion, but this was written a very long time ago and Bob Brandon (a very good philosopher of biology) did most of the heavy thinking.


  1. "what it takes to be the necessary features of languages required for the task at hand". I know this has been talked about before, but why does it have to be "necessary"? Why is it so hard to accept that language (indeed, much of human cognitive capacities) could be just like a peacock's tail, a case of nature going to extremes and well beyond what was "necessary" in response to more limited evolutionary pressures? Not only is this perfectly possible in view of known biology and similiar to other instances of "bizarre" species-particular traits observed in nature, it would basically bridge the gap between radical human particularism and gradualism. As I understand it, when investigating this type of chain of events, there is no need to posit that a particular evolutionary pressure entailed (no pun intended) a particular trait - so long as we can determine that the former set the stage for the sort of mutation that could plausibly have led to the latter.

    1. If I understand the peacock case, the tail grew to its size due to a kind of arm's race: bigger being more desirable for females and given that sex is all that there is on evolution's mind, the fact that bigger meant clumsier was no problem so long as it meant sexier (at least up to a point). Ok, tell the same story for either of the two properties we've been discussing: recursion means sexier? Really? Or words are what they are because otherwise men could not whisper sweet nothings into potential mates' ears?

      Look, I think that it there is common agreement that having language yields a big advantage (at least if we abstract away from the fact that humans will likely destroy the planet, but recall evolution is myopic). The question is whether this advantage ended up shaping the traits we find. Chomsky has mentioned two traits: hierarchical recursion and NL words with their special properties. Ok, how did they arise? Here's one "answer" Tools; they are there because tools put them there, or the advantage of having sophisticated tools led to language with these properties. All I want are the details, or some of them. I don't see the causal link. Now here's a link I can see: these two features of NL arose "genetically" (i.e. by magical happenstance) and once they arose they brought all sorts of advantages, among these being better tool making. So the reason the genetic miracle stuck was the advantages it brought. NOBODY would find this story terrible, except for two things: first, specify what the change was and how it yielded FL/UG (that's Minimalism, Chomsky's contribution) and this story has little to do with natural selection. The latter is a story which explains why we have the properties war have given selective advantages. But this is precisely the kind of story that nobody is putting forward. And that's Chomsky's (and my) point. Details, or at least some. Hopes and prayers are nice, but they are a little spare on a cold winter's night.

    2. I suggest that sexual selection should not be written off ... the capacity to produce intricately structured sweet nothings might well be quite seductive, especially if it's an indicator of general cognitive superiority. In our society we have largely forgotten about it, but in many others,poetic love compositions are highly valued.

      It also addresses the problem of how the adaptations for complex language production might have spread, because all you need to get a benefit is an audience that can sort of comprehend and be charmed, rather than a full peer who can use the capacity as well as you can.

    3. I'm not sure I was clear enough. I merely took issue with the use of the "necessity" argument in the review. The point about oversized peacocks' tails is that their exaggerated growth was apparently not "necessary" for anything specifically, merely somewhat advantageous to the bearers of said trait. Somehow, a number of selective pressures (sexual selection, intimidatory signalling to predators, etc.) set the process in motion, and from then on it was blindly reinforced to ever more bizarre levels. Not because they were "necessary" for survival, or a specific "requirement" stemming directly from those selective pressures.

      So it is of course possible that FL, or indeed much of human cognition, might be one such case of an accidental exaggeration of nature, blindly set in motion by selective pressures that did not "require" such an overkill solution in the first place, so to speak. IF that turns out to be the case (I'm not saying it is, but it remains a possibility), it would be futile to ask how a richly structured FL is "necessary" for better tool-making, for example, or anything else for that matter. It would be enough to demonstrate precisely how an increasingly complex FL would be advantageous for it (with further "overly complex" developments deriving indirectly from this, like the peacock's tail). And, for better or worse, that's what the paper tried to do.

      Incidentally, though, I must say I believe the specific hypothesis about tool-making smacks of archeological bias, as complex tools are one the precious few things left to us that attest "modern" behaviour. It is certainly seductive to think that the very same sort of material evidence that happened to survive could have a causal link to modern human cognition, rather than being just a bunch of fragmentary pieces of a much bigger puzzle. Eventually, we will need more. Analysis of ancient human DNA, for example (an area which has experienced a boom in recent years), might help settle the issue.

  2. Although I am happy for my good mate Kevin Laland to have scored another high profile publication (cheers, Kev!) , I agree with Norbert that it is not clear what he big deal is here. In fact, the authors themselves acknowledge this when they state:

    "This leaves open the possibility that the transmission
    of Acheulean technology was reliant on a form of (gestural or
    verbal) proto-language12,60,61. This need not imply that
    Acheulean hominins were capable of manipulating a large
    number of symbols or generating complex grammars. Our
    findings imply that simple forms of positive or negative
    reinforcement, or directing the attention of a learner to specific
    points (as was common in the gestural teaching condition), are
    considerably more successful in transmitting stone knapping than
    observation alone. This is supported by existing theoretical work
    that suggests positive and negative feedback greatly enhances
    the rate of transmission33.

    So, ‘reinforcement’ then, and ‘proto-language’ (whatever that is – you can’t have a bit of infinity, as Noam said in his Colloquium Lecture Q&A) is just a speculative possibility.

    Also, as you can see in the Morgan et al. paper, there is never a significant difference between 'verbal teaching' and pointing. It's not quite clear what they say about the chains. They claim that performance drops without training, and declines steadily with training. But it looks like (fig 2 g, h) that performance is at a low level to begin with, without training, and even verbal training can't stop a decline in performance in the trained groups.

    More importantly, as we note in our forthcoming comment in PLoS Biol: "In contrast, the typical pattern of stasis in stone - tool technology before modern Homo sapiens emerged argues for a lack of language until very recently." Ian Tattersall has written about this quite extensively. Ian has also pointed out on numerous occasions that tool making is perhaps not that big a deal, but that the sudden (and recent) appearance of symbolic objects is. As we put it in the 2014 PLoS Biol paper:

    "In terms of historically calibrated records, this leaves us only with archaeology, the archive of ancient human behaviors—although we have once again to seek indirect proxies for language. To the extent that language is interdependent with symbolic thought [20], the best proxies in this domain are objects that are explicitly symbolic in nature. Opinions have varied greatly as to what constitutes a symbolic object, but if one excludes stone and other Paleolithic implements from this category on the fairly firm grounds that they are pragmatic and that the techniques for making them can be passed along strictly by imitation [31], we are left with objects from the African Middle Stone Age (MSA) such as pierced shell beads from various ,100,000-year-old sites (e.g. [32]) and the ,80,000-year-old geometrically engraved plaques from South Africa’s Blombos Cave [33] as the earliest undisputed symbolic objects. Such objects began to be made only substantially after the appearance, around 200,000 years ago, of anatomically recognizable H. sapiens, also in Africa [34].

    1. The presumed interdependence of "symbolic thought" and I-language is a crucial point here. Johan, can you comment further on what evidence (if any) we have that other species indeed lack "symbolic thought" of the relevant kind? Also, what is the working definition of "symbolic object" assumed here? I checked the Tattersall article cited, but it, too, appears to rely on an intuitive notion. Thanks.

    2. @ Dennis O. As we say in the paper, "although we have once again to seek indirect proxies for language". I assume it is clear from our essay that the whole enterprise of reconstructing language evolution has to make do with very little information. We don't say that 'symbolic thought' and i-language are one and the same, as you can see from the above quote ('indirect proxies'). As we say, "Opinions have varied greatly as to what constitutes a symbolic object", but I think that Ian's suggestions (in his books) are reasonable. If you want to investigate the possibility of language in non-human animals, the logical way is to define what you mean by language and try to find that in animals - rather than studying indirect proxies for language. When it comes to language evolution, however, indirect proxies is all you've got.

  3. I don't know enough about this stuff, but would defining something like PRE-MERGE not help in these proto-cases? Signs are just more tools (maybe?). But, MERGE seems to go one step further (up the ladder of idealization... I guess?) Or not :-)

  4. For example, Patel's Snowball is hardwired for dancing, word-world talk and tool-making but not for choreography, math and NL etc.?