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.
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.
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.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
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 […].”
“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).
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.
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.