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.

Studying the Evolution of Cognition and Language: Are We Wasting Our Time? (Part 1)

This is my penultimate post in my short series on human uniqueness (1, 2, 3).

In a recent article in nature, Johan J. Bolhuis and Clive D. L. Wynne asked “Can evolution explain how minds work?” (subscription needed) and were of the opinion that there are severe problems with comparative paradigms. They pointed out major problems with evolutionary interpretations of cognitive traits. In their view, this research was fraught with anthropocentrism, e.g. it was mostly focused on humans or seen from a human perspective, and it doesn’t take into account the problem of convergent evolution:

“Different species may have arrived at similar solutions to cognitive problems because they have experienced similar selection pressures, not because they are closely related. In other words, evolutionary convergence may be more important than common descent in accounting for similar cognitive outcomes in different animal groups” (Bolhuis & Wynne 2009).

In addition, we don’t know which selective pressures our ancestors faced in their environment. Cognitive traits also leave little to no traces in the fossil record. This means that we mainly have to guess which cognitive traits may have evolved in response to some presumed selection pressures.

Bolhuis and Wynne also hold that comparative researchers have “naïve evolutionary presuppositions” and hold that

“As long as researchers focus on identifying human-like behaviour in other animals, the job of classifying the cognition of different species will be forever tied up in thickets of arbitrary nomenclature that will not advance our understanding of the mechanisms of cognition.” (Bolhuis & Wynne 2009).

This argument is of course not new and can be found – in an even stronger form and on a more general level – in the critical writings of Noam Chomsky, Stephen Jay Gould, and maybe most vocally, Richard Lewontin. Lewontin even goes so far as to say that the only thing we know about the evolution of human cognition is precisely that it evolved. That’s it. (Lewontin 1998: 108). This is especially so with complicated cognitive traits like linguistic competence.

We don’t even know in how far language is an innate genetically specified ability and in how far it is only a by-product of other evolutionary changes and is shaped and specified by culture. What’s more, we can’t possibly know how hereditary mechanisms (both genetic and cultural) acted in our remote ancestor, and we don’t know anything about the survival advantage these presumed mechanisms may have had in the past. Lewontin draws the conclusion that “reconstructions of the evolutionary history and the causal mechanisms of linguistic competence […] are nothing more than a mixture of pure speculation and inventive stories.” (Lewontin 1998: 111).

He explicitly directs his criticism at proposals like that of Pinker & Bloom (1990) (see also this post) who argued that natural selection is the only force that can explain the evolution of such a ‘complex adaptive’ trait like language. But we can’t show how natural selection might have been at work in each of the unknown stages that were necessary for language to evolve. Consequently, Pinker & Bloom’s argument is flawed.

I think Lewontin’s argument applies to some of the sweeping ‘adaptationist’ evolutionary approaches to language and cognition. But I don’t think his 1998 critique really captures the state of the research today or even earlier. In the 2003 anthology ‘Language Evolution’ (Kirby & Christiansen 2003, see also this post) which pretty much presented the state of the field there were many researchers who had a substantial amount to say about the evolution of language without falling into the theoretical pitfalls Lewontin warned about. At the end of his article Michael Tomasello, for example, cautions that “I am afraid that I have no real evolutionary fairy tale with which to conclude.” But he still has to clarify what valuable implications his research has for a general account of the evolution of language and cognition and is able to spell out some of the cognitive mechanisms which had to evolve and in how far culture has been an important aspect in this respect (Tomasello 2003: 108f.). Similarly, Marc Hauser and W. Tecumseh Fitch voice similar criticism to that of Lewontin and Chomsky (which is not very surprising given that they co-authored two papers with the latter). However, they hold that the “comparative approach to language has been and will continue to be a powerful approach to understand both the evolution and current function of the language faculty.” (Hauser & Fitch 2003: 159). I completely agree with them, especially if we throw developmental science into the mix. By looking at non-human primates we are able to “isolate and study those components of the language faculty inherited from our non-human ancestors” (Hauser & Fitch 2002: 159). What is more, comparative research can also give us insight into possible advantages and selection pressures that led to the evolution of features. If we find similar traits and neural subsystems in other primates it is reasonable to assume that these are homologous and due to our shared evolutionary history. If on the other hand, other primates don’t have these traits but other species, e.g. songbirds, jays, parrots or deer, have them, they may be analogous and due to similar environmental or social selection pressures. If we carefully compare many different species across different taxa we get an increasingly better picture of the evolution of cognition in humans and other species.

But a broad survey of the field shows that this is already done as Sara Shettleworth (2009a) points out. Consequently, Bolhuis and Wynne’s criticism falls apart if we actually look at the field they are criticising and it is more as if they are flogging a dead horse (2009b). But we can see that Tomasello, Hauser, Fitch, Bolhuis, Wynne and Shettleworth all think that comparative cognition can give us important insights into the evolution of the organisms they study and compare. But it has to be done carefully and critically and within a throroughly worked out theoretical and methodological framework. In light of this, much of Lewontin’s criticisms seem to be misguided or at least do not really apply anymore. But does this really mean that there are no real general problems with evolutionary inquiries into the evolution of cognition?

In my next post I will address the additional criticisms Lewontin launches at the study of the evolution of cognition.

References:

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

Hauser, M. D. & Fitch, W. T. (2003). What are the uniquely human components of the language faculty? In: Language Evolution: The State of the Art. Ed. by Christensen, M. & S. Kirby) pp. 158-181. Oxford: Oxford Unviersity Press.

Normal 0 21 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

Pinker, Steven & Paul Bloom (1990): “Natural Language and Natural Selection.” In: Behavioral and Brain Sciences 13.4: 707-726.

Shettleworth, S. J. (2009a). The evolution of comparative cognition: Is the snark still a boojum? In: Behavioural Processes , 80, 210-217.

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

Tomasello, M. (2003). On the different origins of symbols and grammar. In Language Evolution: The State of the Art. Ed by. M. Christiansen & S. Kirby. Oxford: Oxford University Press.

Michael Tomasello - Why We Cooperate

Michael Tomasello has a new book out in October called "Why We Cooperate." What is interesting about this publication is that Tomasello presents his findings on great ape and infant cognition and and social and developmental psychologist Carol Dweck, anthropologist Joan Silk, philosopher Brian Skyrms, and developmental psychologist Elizabeth Spelke respond to and explore the implications of his work in light of their own research.

Here's the description:

"Drop something in front of a two-year-old, and she's likely to pick it up for you. This is not a learned behavior, psychologist Michael Tomasello argues. Through observations of young children in experiments he himself has designed, Tomasello shows that children are naturally—and uniquely—cooperative. Put through similar experiments, for example, apes demonstrate the ability to work together and share, but choose not to.

As children grow, their almost reflexive desire to help—without expectation of reward—becomes shaped by culture. They become more aware of being a member of a group. Groups convey mutual expectations, and thus may either encourage or discourage altruism and collaboration. Either way, cooperation emerges as a distinctly human combination of innate and learned behavior.

In Why We Cooperate, Tomasello's studies of young children and great apes help identify the underlying psychological processes that very likely supported humans' earliest forms of complex collaboration and, ultimately, our unique forms of cultural organization, from the evolution of tolerance and trust to the creation of such group-level structures as cultural norms and institutions.

Scholars Carol Dweck, Joan Silk, Brian Skyrms, and Elizabeth Spelke respond to Tomasello's findings and explore the implications."

Some Links

The Exploratorium (in San Francisco) and the Max-Planck-Institute for Evolutionary Anthropology have a nice site up called "Exploratiorium Evidence: How Do We Know What We Know?"

"Science is an active process of observation and investigation. Evidence: How Do We Know What We Know? examines that process, revealing the ways in which ideas and information become knowledge and understanding.
[...]
In this case study in human origins, we explore how scientific evidence is being used to shape our current understanding of ourselves: What makes us human—and how did we get this way?"

Hat-tip: Afarensis

Sandy G of The Mouse Trap also has a nice post up called "What is it like to be a zombie?"

Also, Ed Yong of Not Exactly Rocket Science reports on research which found that Chimps use Swiss army toolkit to rob beehives
I find the possible implications of the fact that chimpanzees use several multi-functional tools for honey-extraction quite fascinating.
As I've written before (see also this post), linguists like Dieter Wunderlich argue that the ability to change an existing structure and then further work on the qualitatively changed output in a hierarchical, recursive, and compositional manner - as for example exemplified by crafting hand axes - is a precursor to or even the same process athis the compositionality found in language. If chimpanzees are able ts io work with and modify tooln a compositional manner this would provide another insight into the possible cognitive platform from which language evolved.

The Nature and Evolution of Human Cognition: Considerations from Comparative and Developmental Psychology

If we bear in mind the proposals for what (among other things) makes human cognition unique I summed up in my last post – along with the conjecture that our cognitive style may more be something of a idiosyncrasy due to a highly specific cognitive specialization instead of a definitive quantitative and qualitative advance over other styles of animal cognition, we can look for studies which further point in that direction.

Chimpanzees, for example, beat humans at certain memory tasks (Inoue & Matsuzawa 2007) and behave more rational in reward situations (Jensen et al. 2007). In addition, it has been shown that in tasks in the social domain, which are generally assumed to be cognitively complex, domesticated animals such as dogs and goats (Kaminski et al. 2005) fare similarly well or even outperform chimpanzees. It is entirely possible that the first signs of human uniqueness where first simply side-effects our self-domesticating lifestyle – the same way the evolution of social intelligence in dogs and goats is hypothesised to have come about –, acting on a complex primate brain (Hare & Tomasello 2005).

It is certainly a fact

“that Homo sapiens has become ‘localized’ by having to depend upon learned, culture-specific modes of interacting.” (Bruner 2005: 693).

Humans are constantly immersed in culture and social interactions and at the same time extremely dependent on it, and human ontogeny fundamentally differs from that of any other primate species. Human infants are even more helpless and completely dependent on others, and remain unable to feed and care for themselves for a uniquely long time span. Furthermore, childhood and adolescence are two additional and prolonged states of mental development and cultural learning absent in any other species that seem to be vitally important for the development of culturally adept and cognitively highly sophisticated human beings (Locke & Bogin 2006).

The fact that social interaction, learning, and cultural transmission play such a vital and important role for children’s ongoing cognitive development indicates that hey have a biologically-based “adaptation for culture” which has to be operative from early on. Comparing young children’s and infants cognitive abilities with that of the other great apes may be a useful indicator of the biological foundations of what makes us uniquely human. In Addition, we can gain crucial insights on what platform the evolution of human cognition could have started because chimpanzees are “conservative species” that has always lived in tropical forests, which is why they didn’t have to change as much as we did to adapt to fundamentally new environments and selection pressures. This also means that chimpanzees are more similar to the last common ancestor we shared with them than we are (Gazzaniga 2008: 51).

If we now compare the performance of 2.5 year-old children and other great apes (in this case chimpanzees and orangutans) across a wide range of domains we indeed find that in some domains the differences are much more marked than in others. (see also, this post). In the physical domain, which includes the understanding of space, quantity and causality, the subjects were tested by rewards that were out of reach and could only be retrieved with a stick (causality), or had to locate a reward that was not directly accessible but had to be located (space). In the social domain, subjects had to follow “an actor’s gaze direction to a target,” solve “a simple but not obvious problem by observing a demonstrated solution” (social learning), or understand what an actor intended to do, but in the end failed to. (Intention attribution or Theory of Mind).

Generally, orangutans fared worst in most of the test, whereas chimpanzees and humans were quite similar in the physical domain. In some of the physical tasks, especially the one which required active tool use, chimpanzees even out performed human children. But in the causality tasks in which

“a judgment must be made before manipulation or choice” (Hermann et al. 2007:1362)

children were better. They were also better in inhibitory and cognitive control in general, something that is expected given what we know about the disproportionate dominance and prominence of higher-order prefrontal circuitry, which better enable a child’s brain

“to coordinate processing among its millions of neurons in order to direct them toward future goals.” (Miller et al. 2002: 1131)

than is the case in other great apes. According to the research group that did these experiments

“the current results provide strong support for the cultural intelligence hypothesis that human beings have evolved some specialized social-cognitive skills (beyond those of primates in general) for living and exchanging knowledge in cultural groups: communicating with others, learning from others, and “reading the mind” of others in especially complex ways“ (Hermann et al. 2007: 1365).

But as indicated by children’s performances in the causality task, and in congruence with the models of human cognition I’ve outlined above, the social domain is not the only catch-all distinctive property of human minds. Instead, the ability to re-interpret cognitive data in terms of more abstract properties such as “unobserved causal forces” and “mental states” seems to be distinctive foundation for excelling performances in both the physical and social domains. The authors find it plausible however, that

"understanding hidden causal forces evolved first to enable humans to understand the mental states of other persons, and this generalized only later to the physical domain.”

This is why we are justified in further looking for uniquely human attributes in the socio-cognitive development of children.

References:

Normal 0 21

Bruner, Jerome (2005): “Homo Sapiens, a localized species”. In: Behavioral and Brain Sciences 28:5, 694–695.

Gazzaniga, Michael S. (2008): Human: The Science of What Makes us Unique. New York: Harper-Collins.

Hare, B., & Tomasello, M. (2005). Human-like social skills in dogs? Trends in Cognitive Science, 9, 439-444.

Hermann, Esther, Josep Call, María Victoria Hernández-Lloreda, Brian Hare, and Michael Tomasello. 2007. “Humans Have Evolved Specialized Skills of Social Cognition: The Cultural Intelligence Hypothesis” Science 317: 1360-1366.

Inoue S. and T. Matsuzawa (2007). Working memory of numerals in chimpanzees. Current Biology, 17(23), R1004-R1005.

Jensen, Keith, Josep Call and Michael Tomasello (2007): Chimpanzees Are Rational Maximizers in an Ultimatum Game. Science 318: 107-109

Kaminski, Juliane, Riedel, J., Call, J. & Tomasello, M. (2005) Domestic goats (Capra hircus) follow gaze direction and use social cues in an object choice task. Animal Behaviour, 69(1), 11-18.

Locke, John L. and Barry Bogin. (2005) “Language and life history: A new perspective on the development and evolution of human language” Behavioral and Brain Sciences 29, 259–325.

Miller, Earl K., David J. Freedman and Jonathan D. Wallis (2002.) “The Prefrontal Cortex: Categories, Concepts and Cognition.” In: Phil. Trans. R. Soc. Lond. B 357: 1123–1136.

News on FOXP2

There are some interesting posts on new work done on FOXP2. The human version of the gene, which is implicated in vocal coordination and language in some way among a lot of other functions, was inserted into mice who also possess a version of foxp2 that influences, among other things, erly ultrasonic vocalizations. The brain led to changes in neural organization but otherwise bodily development was normal. One implication of this is that the changes in the human version of FOXP2 probably affect neural development, which is quite an ecxiting find.

There are posts on the paper by Enard et al. over at:

Anthropology.net

Gene Expression

The Loom

Update:

Ed Yong of Not Exactly Rocket Science also has a nice post up on the topic

Six Candidates for What Makes Human Cognition Uniquely Human

One of the key candidates for what makes human cognition unique is of course language and symbolic thought. We are “the articulate Mammal” (Aitchison 1998) and an “animal symbolicum” (Cassirer 2006: 31). And if one defining feature truly fits our nature, it is that we are the “symbolic species” (Deacon 1998). But as evolutionary anthropologists Michael Tomasello and his colleagues argue, “saying that only humans have language is like saying that only humans build skyscrapers, when the fact is that only humans (among primates) build freestanding shelters at all” (Tomasello et al. 2005: 690).

Language and Social Cognition

According to them and many other researchers, language and symbolic behaviour, although they certainly are crucial features of human cognition, are derived from human beings’ unique capacities in the social domain. As Willard van Orman Quine pointed out, language is essential a “social art” (Quine 1960: ix). Specifically, it builds on the foundations of infants’ capacities for joint attention, intention-reading, and cultural learning (Tomasello 2003: 58). Linguistic communication, in this view, is essentially a form of joint action rooted in common ground between speaker and hearer (Clark 1996: 3 & 12), in which they make “mutually manifest” relevant changes in their cognitive environment (Sperber & Wilson 1995). This is the precondition for the establishment and (co-)construction of symbolic spaces of meaning and shared perspectives (Graumann 2002, Verhagen 2007: 53f.). These abilities, then, had to evolve prior to language, however great language’s effect on cognition may be in general (Carruthers 2002), and if we look for the origins and defining features of human uniqueness we should probably look in the social domain first.

Corroborating evidence for this view comes from comparisons of brain size among primates. Firstly, there are significant positive correlations between group size and primate neocortex size (Dunbar & Shultz 2007). Secondly, there is also a positive correlation between technological innovation and tool use – which are both facilitated by social learning – on the one hand and brain size on the other (Reader and Laland 2002). Our brain, it seems, is essential a “social brain” that evolved to cope with the affordances of a primate social world that frequently got more complex (Dunbar & Shultz 2007, Lewin 2005: 220f.). Thus, “although innovation, tool use, and technological invention may have played a crucial role in the evolution of ape and human brains, these skills were probably built upon mental computations that had their origins and foundations in social interactions” (Cheney & Seyfarth 2007: 283).

Language, Mental Representations, and Symbolic Thought

But this of course does not mean that we expect all other unique aspects of human cognition to be derivative of social cognition. The development of higher social cognition only presented the enabling context and cognitive starting point for other human mental capacities to evolve. To pick up the example again, language, for instance, does not only have an interactive function but also a symbolic one. It creates ‘symbolic assemblies’ that function as form-meaning pairings (Evans & Green 2006: 6f.). But the ability to acquire arbitrary symbolic units itself does not appear to be uniquely human, as it has been demonstrated in great apes, parrots, dolphins and dogs (see Tomasello 2008: 254ff.). But there are two essential differences between the symbolic abilities of humans and other animals: First, even with lexigram- or sign language-trained apes there appears to be nothing that even comes close to the production and joint engagement skills possessed by human children (production) or even pre-verbal infants (joint engagement) (Tomasello 2008: 109ff.).

Secondly, human symbols and concepts function as ‘decoupled representations’ which are not directly bound to a reaction pattern as in most other animal species, including symbol-trained animals, and enable significant “response breadth” and planning (Sterelny 2003: 29f.). In addition, symbolic thought and linguistic usage does not only rely on the comprehension and production of arbitrary signs, but essentially depends on our capacity for abstract, relational, analogical, higher-order, hierarchical and role-governed compositional thought. (Deacon 1998, Jackendoff 2007, Penn et al. 2008).

We now have two tentative candidates for what makes us special:

(1) The capacity to develop a shared point of view or “we-perspective” (Tuomela 2007: 46f.) and jointly engage in and attend to shared goals, plans and intentions in a cooperative collaborative activity within a joint attentional frame and a shared frame of reference (Tomasello et al. 2005).

(2) A conceptual system that is able to reinterpret and re-describe sensory as well as cognitive data and store them in an abstract, decoupled format that can be used for symbolic, relational and analogical reasoning (Penn et al. 2008).

We can now imagine a step in evolution where these two capacities were further integrated, yielding the analogical realization that others are “like me” (the capacity developed to

(3) actively attribute mental states to others in the same sense as one experience mental events and states oneself, that is to, have a “theory of mind” (Premack & Woodruff 1978).

Further, an integration of these capacities, and continuing collaborations and mutual engagements in social and other activities, would lead to the emergence of

(4) shared, intersubjectively overlapping frames of references or coordinate systems into which abstract and non-abstract conceptual representations could be integrated and imported in a systematic fashion, and within which shared percepts and concepts could be blended, unified, and related to each other in a role-governed fashion. (Bühler 1934, Fauconnier & Turner 2002).

In short, the first species in the hominin line who developed this capacity would not only have shared a perceptual world with his or her conspecifics, but they would inhabit a shared mental world. In this collective “we-perspective” and shared frame of reference mediated by joint engagement, they would then be able to create a shared “symbolic niche” in which meaningful cultural practices and shared symbolic constructs, such as institutions, could be co-created and which would ‘come alive’ and have actual real-world significance (Harder fc, Tuomela 2007). By jointly attending to and attaching meaning to cultural artefacts and practices homo gave them intersubjective value and reality and created ‘institutional realities’ (Searle 1995, Moll & Tomasello 2007). It is probable that from the dawn of human culture cognition accelerated in a spiralling and cumulative cognition-culture feedback loop

Additionally, when we are able to project ourselves and others into the same frame of reference, and can also project more abstract symbolic units into this coordinate system, it follows that along and co-evolving with these other changes a capacity

(5) for projecting ourselves and others backwards or forwards into past and future situations is probable to have evolved, that is, a capacity for mental time travel, including the ability to retrieve and re-live episodic memories of past autobiographical events (Tulving 2005) as well as prospective foresight enabling the planning of future actions and events (Suddendorf & Corballis 2007).

Finally, these changes were certainly accompanied co-evolutionary by a means of externalising shared proto-concepts and communicatively coordinating cooperative activities in a flexible manner via the vocal and gestural level. (Hurford 2007, Tomasello 2008). At some time, concepts became public, that is “they became the sorts of things that lots of people can, and do, share” (Fodor 1998: 28).

It is conceivable that “building upon pre-existing representational schemes in animals” (Hurford 2007: 140), and a general perceptual and cognitive machinery that scaffolded them (Jackendoff 2007: 388), ever increasing linguistic abilities and concepts evolved step by step. They probably did evolve from the proto-concepts we can see in the higher mammals of today into the pre-linguistic concepts that are argued to exist in some of the other great apes (especially those individuals who are enculturated and symbol-trained) and then into some form of proto-language (Bickerton 2009). At some time, this proto-language with already quite sophisticated conceptual representations then evolved into the fully human language we know today.

In summary, a truly human language faculty evolved, which is

(6) a collection of unique mental structures – phonology (externalisation) and syntax (merging constituents (A + B = [AB] and creating blended new ‘mental building blocks’ which can be merged with other constituents recursively [AB] + C = [ABC]) – and the interfaces between these mental structures and the conceptual system. These “specific unique building blocks for phonology, syntax, and their connection to concepts” are what makes language and language acquisition possible (Jackendoff 2007: 388f.).

This account of course has not mentioned important ecological factors (e.g. navigation, foraging, predator avoidance) that will have contributed to these developments and constructed niches in which these factors could develop further and faster. In the case of language, for example both “fast processing and mapping from hierarchical structure to temporal ordering,” which are two fundamentally important features of human language, “can be attributed to progresses in the timing of actions necessary for producing and using hand axes, [as well as throwing] that is, to sensomotoric skills that could have been adapted for language” (Wunderlich 2006). Support for this thesis comes from the fact that PET scans have shown a that there is neural circuitry supporting and involved in both language production and early stone age tool-making (Stout et al. 2008, see also here).

It also fits with our general model that there is mounting evidence “that much temporally sequenced hierarchical structure is constructed by the same part of the brain […] whether the material being assembled is language, dance, hand movements, or music (Jackendoff 2007: 388). Additional work on mirror neurons, motor neurons that activate both when an action is performed and observed (Rizzolatti & Craighero 2004), points in the direction that they are involved in understanding the goal-related actions of others in a social context. The evolution of a Mirror Neuron System for understanding actions and intentions may have been a crucial part of the cognitive development that made human thinking possible.

This is also supported by the fact that the human conceptual system has two distinctive properties: One the one hand it enables abstract, relational, role-governed, symbolic thinking (Penn et al. 2008). But at the same time human concepts are still deeply rooted in, based on, and grounded in embodied sensori-motor experience (Barsalou 1999, Gallese & Lakoff 2005). This holds even for linguistic concepts and metaphors, which have been shown to be partly grounded in embodied cognition (Lakoff & Johnson 1980). To get back to language, a final indicator of the connectedness of social interaction and parts of higher-order cognition comes from proposals that “neural circuits doing computations to control the hierarchy of goal-related actions were ‘exploited’ to serve the newly acquired function of language syntax” (Gallese 2007: 666).

Now that we have some theoretical proposals on crucial aspects of human uniqueness (although this list is far from being definitive and exclusive), we can see in how far they are borne out by the comparative and developmental data that is available.

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