Evolutionary Context for the Human Brain

by Edward Quinn

MacKinnon and Fuentes (2012) draw on the literature of primatology to place human sociality in a broader phylogenetic context. This context allows us to understand humans as part of a pattern in evolutionary history, which associates increased sociality with increasingly large brains. Placing ourselves within larger evolutionary patterns also allows us to see how our social behavior might be different from that of non-human primates. What is clear in this chapter is that behavioral flexibility has allowed many different primates to exploit myriad environments in many different ways. MacKinnon and Fuentes (2012) use the example of variation in food processing within the same species in the same type of environments to illustrate this point. This variation must be understood not only in terms of ecology, but also in terms of the social traditions of particular groups within species.
 
The authors illustrate the use of theories and methods like niche construction and social network analysis for a better understanding of how social and ecological selective forces are integrated in the production of the social primate brain, and how this brain enhances selective fitness. The particularly long period of post-natal brain growth in genera like Homo, Pan, and Cebus allows for the deep integration of social learning into the developing brain. This period of development is crucial for learning how to navigate (social) selective landscapes successfully, which call simultaneously for competition and cooperation with variable actors. The authors ultimately agree with scholars like Dunbar, arguing that social intelligence (enabled by expanded brain volume and longer periods of postnatal brain development) was a major determinant of darwinian success in human evolution.
 
I found the niche construction section of this reading useful. Rather than conceiving of social competitors, foraging problems, predator avoidance, etc. as independent selective pressures calling for specific adaptive strategies on the part of the individual, it is useful to think about how social behavior and ecology are integrated. Niche construction theory helps to provide a plausible account of how human brain evolution could have occurred; however, I am left wondering if the social brain hypothesis isn’t another “just-so” story. It is certainly conceivable that larger brains enabled more cooperation, increasingly complex communication, more efficient exploitation of the environment, a greater range of exploitable habitats, etc., but how could we disprove this hypothesis?
 
I might be more convinced by the social brain hypothesis if there were neurological models of how the social brain could have developed through evolutionary time. What specific changes occurred in brain structure and circuitry in human evolutionary history that allowed for the development of such a uniquely social brain? It is necessary to talk about changes in brain volume, but this only part of the story. I think this is the sort of perspective a neuroanthropologist might contribute to primate studies of cognition and the social brain hypothesis.
 
I am admittedly ignorant when it comes to methodology in primate studies, but I assume primate studies work with small samples, often in an artificial laboratory environment, with evidence from the field sometimes taking the form of anecdotes. I was therefore impressed with some of the literature cited having to do with social network analysis. In particular, I was impressed by the very large amount of data being integrated into the study of primate social networks related to kinship, particular behaviors such as grooming, and how these different networks interact to produce population level patterns in social behavior. This reading left me with an improved impression of primatology studies.
 
This chapter clearly demonstrates the utility of theory and method in primatology for a better understanding of humans. It helps us answer big questions: why are humans so social? Where does our capacity for culture come from? Thus, taking the brain as a given in neuroanthropological research would be a mistake. More productive research will no doubt conceive of the brain as a product of specific evolutionary processes, which impact on how our brain develops and functions in everyday settings. This is a tangible contribution of primatology to neuroanthropology, and this area of research deserves further investigation.
 
References
 
MacKinnon, Katherine C., and Agustín Fuentes
   2012    Primate Social Cognition, Human Evolution, and Niche Construction: A Core Context
               for Neuroanthropology. In The Encultured Brain: An Introduction to
               Neuroanthropology. Daniel H. Lende and Greg Downey, eds. Pp. 67-102. Cambridge:
               The MIT Press.