Thursday, June 18, 2009

Studying the Evolution of Cognition and Language: Are We Wasting Our Time? (Part 2)

In my last post I discussed some of the criticisms faced by people interested in the evolution of cognition.
One of the harshest critics is Richard Lewontin, who, at the end of his article "The Evolution of Cognition: questions we will never answer", advises his readers to “
to give up the childish notion that everything that is interesting about nature can be understood. History, and evolution is a form of history, simply does not leave suffcient traces, especially when it is the forces that are at issue. 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.. (Lewontin, 1998: 130).”
But what leads Lewontin to conclude his essay in such as pessimistic and definitive manner?
According to Lewontin, there are three main strains of evolutionary explanations. And with each strain there are problems with evolutionary inquiries into cognition.

Historical Explanations
Firstly, there is a strain that explains the patterns of similarities and differences between animals through historical relatedness. Humans, for example, are more similar to and share more traits with chimpanzees than with lemurs because the human/chimpanzee lineages split some 5-7 million years ago and the lemur/human lineage split some 78 million years ago.

Functional Explanations
Secondly, there is a strain that tries to explain these patterns by looking at the functions they perform and the adaptive advantage they may have. The bodily similarities of sharks, dolphins, seals, and penguins for example can be explained by the fact that their bodies are adapted to swimming in the sea. Similarly, the differences between closely related species can be explained by adaptations to different environments. The differences between cows, goats, and deer, for example, only arose in the last 10 million years due to the different environments they had to adapt to. (Lewontin 1998: 116).

Problems for Studying the Evolution of Cognition
This is of course a problem for studying the evolution of cognition. Chimpanzees are the closest relatives that still exist but we and them may both have diverged so far from our ancestors that studying the cognitive differences between us may not really give us an insight into much human evolution. Indeed, there even is a study claiming “
more genes underwent positive selection in chimpanzee evolution than in human evolution.” (Bakewell et al. 2007).
Overall,
“Humans and chimpanzees are nevertheless very similar in their proteins, on the average, but vastly different in the sizes of their brains and their ability to write books about each other.” (Lewontin, 1998: 117).
But here is a point where I disagree with Lewontin: the research shown earlier indeed indicates that there probably was not a large amount of changes in brain-related genes that led to human cognition:
“This conclusion, however, does not preclude the possibility that substantial accelerations occurred in the evolution of a few nervous system genes during human origins. Indeed, several such examples are known, including genes that control brain size and speech development. (Shi et al. 2006).
And indeed, a recent article based on assumptions similar to that of these researchers and Lewontin, by Derek Penn and his colleagues, (2008) doesn’t see things so negatively as Lewontin but instead sees these considerations as offering a great chance.

If there really is “profound functional discontinuity between human and nonhuman minds” we can ask if there is a core ability that is responsible for it.
For Penn et al. psychological, comparative and developmental studies point towards the conclusion that this cognitive cap
“is largely due to the degree to which human and nonhuman minds are able to approximate the higher-order, systematic, relational capabilities of a physical symbol system.”
Sara Shettleworth (2009), in her critique of Bolhuis & Wynne’s (2009) arguments which are quite similar to that of Lewontin, agrees that
“There is evidence from behavioural studies that many of humans' mental powers are shared by other animals, including simple forms of learning, memory and categorization, and the elements of social, spatial and numerical cognition.
Only against this background does it make sense to propose, as some have, that there is a distinct small set of mental powers that is unique to humans […].”
Other researchers also defend the view that, contrary to Lewontin, we can learn a lot about the evolution of primate and human cognition by comparing different extant species. Jonathan Kenneth Burns (2004), for example, directly attacks Lewontin's arguments in an article on the evolution of Schizophrenia by stating that primatologist Richard Byrne
“has listed the establishing of a reliable pattern of descent as one part of a methodology for inferring the history of primate cognition (Byrne 2000). Many authors have confirmed the close evolutionary relationship between simian and ape species and modern Homo sapiens, with strong data from comparative psychology, molecular biology, and physical anthropology. Thus, cladistic analysis provides us with living relative species with which we can test the hypothesis that there is a heritable variation for social cognition that increases fitness.“ (Burns 2004: 868)
Evolutionary Constraints
But back to Lewontin’s article. The third strain of evolutionary theory he mentions is the one focusing on developmental and physiological constraints in the evolution and development of organisms. In the billion years of vertebrate evolution, for example, no organism ever developed more than four limbs.
Equally, mammals that went back into the sea and became whales and seals, the turned their limbs into flippers and flukes, but still retained their basic mammalian skeletal architecture.
This probably means that there are basic biological constraints because the available material regulates which evolutionary changes are possible, although the functions and activities of organisms and their parts may change quite dramatically over evolutionary time.
It also implies that
“when new functions arise in evolutiom, they often do so through a process of recruiting previously existing organs or physiological activities.” (Lewontin 1998: 117).
But If a trait is unique to one species it may be that we can’t really find any direct precursors and that it thus has no real “observable evolutionary history.”
What is more, we can’t be sure if a similar trait in other species it is far from clear if
"we are dealing with the same trait in the genetic, anatomical, and physiological sense.” (Lewontin 1998).
Platforms for the evolution of human cognition
I would argue however, that studies that show that similar cognitive activities which activate and rely on similar neural systems are a strong candidate for homologous platforms for human cognitive evolution. In fact, we now know that there are strong neural similarities between aspects of the macaque conceptual system and the human once (Gil-da-Costa et al. 2004).
With research like this we can thus probe into the “common architecture” that “underlies the conceptual systems of different species”, and ask how “additional systems” may have extended “human conceptual abilities significantly” (Barsalou 2005).
We also know now that “Communicative Signaling Activates ‘Broca’s’ Homolog in Chimpanzees,” and recent comparative neuroimaging studies have given new and important insights into the evolution of specialized language areas in human evolution. (for a great summary see this post).

Concluding Remarks
These examples lead me to think that we can learn a lot about the evolution of human cognition and language if we draw together the massive amount of data on the subject from all the different disciplines in a coherent and sensible manner. We simply have much more data to work with than at the time Lewontin voices his criticisms. Studying the evolution of cognition is – or has become – more than a ‘Paleofantasy’ in which we simply tell stories because we don’t know enough. Quite to the contrary – often it is the incredible wealth of data from different disciplines that presents the biggest problem.
Sverker Johansson's (2005) gargantuan collection of data relevant to the study of language evolution bears testament to this. The Study of language evolution, after it has moved beyond its ‘adaptationist’ beginnings in the early to mid-nineties – which Lewontin rightly criticized in some respects – is still a developing and growing field and I certainly agree with Willem Zuidema (2005) who states that
“Only when we have precise scenarios of the evolution of language and worked out ways to test empirically the plausibility of one scenario against another, can we conclude . if that turns out to be the case that there are too many alternative scenarios consistent with the available data. In my view, we have certainly not reached this stage yet.”


I hope I can wrap up my discussion of Lewontin's article next week.

References:

Bakewell,Margaret A., Peng Shi, and Jianzhi Zhang (2007:) More genes underwent positive selection in chimpanzee evolution than in human evolution. PNAS 104: 7489-7494.

Barsalou, Lawrence W. 2005. “Continuity of the conceptual system across species.” Trends in Cognitive Science 9.7: 309-311.

Bolhuis, Johan and Clive D. L. Wynne (2009):Can evolution explain how minds work?' Nature 458: 832–833.

Burns, Jonathan Kenneth. (2004) An evolutionary theory of schizophrenia: Cortical connectivity, metarepresentation, and the social brain. Behavioral and Brain Sciences
27(6):831–55; Discussion, 855–85.

Byrne, Richard W.(2000) Evolution of primate cognition. Cognitive Science 24(3):543–70

Gil-da-Costa, Ricardo, Allen Braun, Marco Lopes, Marc D. Hauser, Richard E. Carson, Peter Herscovitch and Alex Martin. 2004. “Toward an evolutionary perspective on conceptual representation: Species-specific calls activate visual and affective processing systems in the macaque.” PNAS 101.50: 17516–17521.

Johansson, Sverker (2005): Origins of Language: Constraints on Hypotheses. Amsterdam: Benjamins.

Lewontin, R. C. (1998) The evolution of cognition: Questions we will never answer. In D. Scarborough and S. Sternberg, editors, An invitation to cognitive science, Volume 4: Methods, models, and conceptual issues. Cambridge, MA: MIT Press

Shettleworth, Sara J. (2009). Cognition: theories of mind in animals and humans. In: Nature 459: 506.

Shi, Pen Margaret A. Bakewell and Jianzhi Zhang(2006):Did brain-specific genes evolve faster in humans than in chimpanzees? Trends in Genetics 22: 608-613.

4 comments:

Doug said...

Hello, again:

The problem with historical explanations for the evolution of cognition is twofold:

1. We don't have any close surviving relatives. (Gorillas, chimps, and us had a common ancestor ~7-10m.y. ago; so there's about 14-20m.y. of independent evolution since then, which, as L. points out, is huge.)

2. We really have no idea who our ancestors were, fossils notwithstanding. There is no clear line we can identify that leads to us.

3. Molecular data can't save us, because the rate of change in coding gene sequences, let alone "silent" gene sequences, given different rates of change, the overall change over long periods of time "averages out." That's why we can use molecular data to make phylogenetic reconstructions in the first place.

So, as L writes, "The evolutionary space is too sparsely populated to be able to connect the points sensibly."

Even tool refinement, as you imply, may not be evidence of biological change, but merely ("merely") of cultural change. As L points out:

"When we consider other evidence of high cognitive function -- language, planning, political organization, technology beyond stone tools -- we have absolutely no evidence. Even fire does not seem to have been domesticated before 100,000 years ago, when our ancestors were already indistinguishable from us morphologically and presumably had begun to feel the chill of advancing glaciers."

On homology vs. analogy: first, have we even defined the trait in question, cognition (or language)? This is, I think, where HCF begin, with a definition that is rigorous: language as infinite recursion. Without defining the trait, you're lost.

(Off topic, but this issue is common in history, and especially in the history of science. Is Democritus' atom the same as Bohr's? Different in degree? Different in kind, and thus incommensurable? An open question.)

It's no small problem, for, as L says, "[W]e must avoid the process of ad hoc adjustment of our definition of cognition so as to include just Homo and a few related genera, for then, by definition, we will invent a characteristic whose evolution is already predetermined by its definition. We must decide to begin by delimiting that "cognitive ability" whose evolution we want to study, and then accept the possibility that it is a de novo state with no homologies in other known organisms." Indeed, and I think that's what HCF try to do.

I'd pay particular attention to section 3.5.3.1, "Linguistic ability." L is well aware of at least kinds of evidence: "...comparative neuroanatomy of related species, the experimental functional anatomy of the brain, and, for humans, information about the function of people who have had various parts of their brain injured, destroyed, or isolated in accidents or as a by-product of surgery."

As L goes on to write, "If we turn to the lower primate brain, where comparative experiments have been performed, there are anatomical homologies to the human language areas and also substantially the same connections between the different areas." He goes on to cite functional similarities and differences (from electrical stimulation studies) to show that vocalization is not necessarily a precursor of language, certainly is not sufficient in itself to be. That's an empirical claim which may be right or wrong, but the point is that we have an issue of evolutionary co-optation (or, "exaptation") -- "In sum, areas of the lower primate brain have been recruited from their former functions to serve the novel functions of speech. We know of no areas of the monkey brain that serve a function that might correspond to speech, nor is it clear what other behavior of monkeys beyond vocalization we would regard as homologous to speech."

[continued]

Doug said...

The widespread feature of recruitment of homolgous structures for de novo functions makes homology vs. analogy very difficult to sort out: "[T]here may be no function at all in the ancestral species that is homologous to the function in the descendants, even though they share homologous anatomical features." This is a big deal, indeed.

I might add that L dispenses with the evolutionary implications of teaching gorillas or chimps sentences as follows: "Dolphins have also been taught to distinguish sentences, for example, the difference between 'Put the ball in the ring' and 'Put the ring on the ball." Yet the Cetacea, the order to which dolphins belong, have been separate from the primates since near the beginning of mammalian divergence, and we are no closer to them evolutionarily than we are to mice."

Basically, L argues that we have to try to teach other related mammalian species language -- or try to, as we have with primates -- in order to make some comparative statement on homology vs. analogy: "Only when a wide range of comparisons over the mammals is available will it be possible to judge the homology of the ape behavior to the human. The choice of our closest hominid relatives for the experiment is simply an anthropocentric bias."

Other issues -- especially re: natural selection. First, foremost, and to me insurmountable is that if you want to argue for anything more than plausibility, you must show how a well-defined trait gave reproductive advantage. Otherwise, you're treating natural selection as a default mode -- really, as a faith, as indeed Dawkins, Pinker, and many others do. That's not science, to me, and it shows little respect for evolutionary theory as it's developed over two centuries. One must reign in one's desire to know; the reigns are what is already known.

Anyway, natural selection operates on variation within species -- on individuals. All due respect to Gould's species selection, even that is more a sorting mechanism than anything else, if even accurate. Thus you can't step back and assume entire species will benefit from any given trait. You can't get away with that.

I'm looking forward to your next blog posting, but I really think that the following sentences should be placed above the desks of every researcher, journalist, interested citizen, etc.: "We should not confuse plausible stories with demonstrated truth. There is no end to plausible storytelling."

Thus, "strong candidates" doesn't really do it. I don't see how any of the other evidence you adduce escapes plausibility and breaks into demonstrated truth, but I'm willing to hear otherwise!

There's an interesting issue here in the development of science, per se. Much of it is luck; much of it is driven by purely irrational desire, and that's not only not a bad thing, but it's also the only option we have, people being driven by irrational desires, at least somewhat. To point this out as a criticism, which I'm not doing, is pure ad hominem -- literally. It's a feature of being human. What I guess irks me is when folks dress up their admirable and quite human desire to know with the honorific, "science." That seems to me no different from saying something is "holy."

Again, I'm plowing through HCF, et al, but from what I can tell, the idea that some kinds of knowledge are just simply beyond our ken is quite rare. And probably for cultural, not biological, reasons.

Michael said...

Doug, thanks for your very substantial comment.

I will try to write a third post this week. But here are some of my thoughts on our objections and comments.

In my opinion, the problems you mention hold for any evolutionary reconstruction and explanation. I don’t see why only the evolution of cognition should be singled out just because it faces additional problems. Fundamentally, the evolution of cognition is not so different from other evolutionary research areas. In all cases we have only inferential knowledge. With the evolution of cognition the stakes may be higher, but there is in my opinion no reason to assume that there is a fundamental impossibility of saying something valuable about the evolution of language and cognition given a worked-out methodology (and there are scholars who develop very clear guidelines and methodologies for these topics, e.g. Rudolf Botha and Alison Wylie, “a philosopher of science [who] describes a methodology that incorporates important scientific principles of hypothesis testing and that is well suited to the challenge of theorising about archaeological.”
Of course we will never know how human cognition evolved. But this is as you already pointed out, mainly an epistemological matter – we will never know anything about past events in some sense – we can only infer what happened by drawing conclusions and making predictions. This holds no matter if we talk about the evolution of language or the evolution bipedal walking. The inferences on some evolutionary topics may be more secure and better modelled – but in all cases do we draw inferences from observed facts given a certain methodology and paradigm.
I don’t know about other fields – but for people in the field of language evolution it is a no-brainer that we will never know how language evolved – but it is still worthwhile to dry to develop models and theories that in turn feed back into conceptions of how we conceptualise language and cognition today.

You’re dead on that one of the biggest problem is defining language and a significant amount of the HCF/PJ/etc. debate circles around this topic. The homology/analogy discussion surely is crucial but.

I guess my aims and that of researchers in this field are at the moment very modest. I don’t think anyone working in this field would think there could ever be something as “demonstrated truth”. In fact, I think this is a scientific impossibility clashing with the usual Popperian and Kuhnian Problems.
I personally just don’t think that there is “no end to plausible storytelling” – I am very content with the idea of synthesising more and more data , developing more and more constrained and fleshed-out models of cognition/language and their evolution, and further looking for support of these models with new predictions and experiments.
It may turn out that there are too many variables and too many definitional pitfalls on the way and we will have a lot of stories that are equally plausible. But we are not at the point that we can say this for sure and I think we can carry useful inquiry into this topic a long long way and learn a lot – I just don’t think positivist imperialism really cuts it when we are interested in elucidating and gaining insight into the evolution of language and cognition. I for now am very happy with the prospect of people developing working, plausible, constrained, predictive, and largely interdisciplinary models of language evolution without aiming for some illusory absolute truth which is beyond the scope of evolutionary theory.

Michael said...

oh and just a minor quibble: There is by now evidence for controlled fires about 800,000 years ago and anthropologists like Richard Wrangham infer it to be even older than that. http://www.slate.com/id/2219162/

Results like this can indeed constrain and even falsify theories on human evolution which is why I think that by continually synthesising data from various disciplines we can indeed move beyond mere storytelling.