‘The Social Brain’ — Cognitive Evolution
‘Cognition’ describes the acquisition, processing, and understanding of information or experiences, and is subject to vast environmental pressures — for instance, the social environment (De Houwer et al., 2017). The vast majority of the world’s species engage in social interactions to varying degrees — whether a simple mating opportunity, or group culture, with adaptive advantages for survival, reproduction, and species advancement.
The ‘Social Brain Hypothesis’, proposed by Dunbar in 1998, describes how natural selection likely favours larger brains as a mechanism for coping with the cognitive demands of interacting in a complex social network (Dunbar and Shultz, 2007). Prior to this, most ideas regarding cognitive evolution centred around the need to process non-social aspects of ecological information, including features such as recognition, perception, and problem solving (Dunbar and Shultz, 2007). However, Dunbar’s 1998 analysis considered the variation in brain size across taxa, noting that substantial differences in neocortex ratio (involved in sensory perception, motor control, language, and spatial reasoning) were observed in animals sharing a similar ecological environment. The brain is an energetically taxing organ, using around 20% of an organism’s energy intake. Thus, it is unlikely that a large brain will evolve without strong selection (Dunbar, 1998). Hence, there must be some other variable among taxa driving this variation in relative brain size.
One idea regards ‘tactical deception’, or simply, the ability to believe in something intangible (Dunbar, 1998). In human societies, this is evidenced in the notion of religion, or myth. Harari’s (2014, pp. 22–44) anthropological review references this with respect to the cognitive revolution, whereby the ability to exist as a social unit, and form coalitions between multiple groups, rests on the cognitive capability to share a common system of belief. However, while this has potential to be true for humans, the extent to which this hypothesis can be generalised to other taxa is limited, as belief cannot be quantified.
A more measurable gauge of sociality is pair-bonded monogamy (having only one mating partner). Dunbar and Shultz (2007) demonstrated significantly greater brain encephalization in three orders of mammals (carnivores, artiodactyls, and bats) and a wide variety of avian species exhibiting pair-bonded mating systems versus counterparts with a different mating system (fig. 1.). But, why is pair-bonding so cognitively demanding? Monogamy can be risky (in regard to passing on the most genes to the following generation) and a poor-quality mate choice can result in disproportionate parental investment — hence selection may favour more synchronous parenting strategies, where physical and cognitive output of individuals must be equal. Acting as a unit in this way may demand greater cognition in the individual, due to shared intentionality and behavioural synchrony, resulting in the need for larger brains (Dunbar and Shultz, 2007).
Furthermore, by categorising the social brain as a result of pair-bonding, we can begin to understand some of the variation among taxa, including the cognitive advancements of primates — including ourselves. Many primate social relationships are dynamic, and individuals are capable of forming pair-bond-like associations in non-reproductive groups and same-sex pairs — thus resulting in a positive correlation between the size of these bonded networks and brain size (Dunbar and Shultz, 2007). This may also help to explain why there was no significant difference found in residual brain volume between pair-bonded primate species and other mating systems (fig.1).
Dunbar’s research focuses on animal groups that the Social Brain hypothesis successfully applies to (particularly human and non-human primates) and sociality as an instigator for cognitive evolution is often disputed in other organisms. Hence, it could be conceived that humans have more advanced cognition due to their need to construct and respond to the fluid relationships between themselves — a quality not attributed to many other animals. Humans have the capacity to adopt the point of view of another individual, forming an understanding that other beings are like themselves with equally complex and emotive mental lives (Tomasello, 2009, pp. 6). Through this shared intentionality, humans have the ability to construct shared goals, beliefs, and can collaborate more effectively on hypothetical concepts or fictions. Throughout the Cognitive Revolution, this enabled Homo sapiens to form larger groups, increasing their survival and success as a species (Harari, 2014, pp. 22–44). While the Social Brain hypothesis remains a topic for debate, it is fascinating to imagine that, without the societal structure that so clearly defines us as human, our cognition would not be as advanced.
References
De Houwer, J., Barnes-Holmes, D. and Barnes-Holmes, Y., 2017. What is cognition? A functional-cognitive perspective. Core Processes of Cognitive Behavioral Therapies. [Online]. Accessed 13 March 2018. Available from: TinyURL.com/y8hxkr5a
Dunbar, R. I. (1998), The social brain hypothesis. Evol. Anthropol., 6, pp. 178–190.
Dunbar, R.I.M. and Shultz, S. 2007. Evolution in the social brain. Science. 317(5843), pp.1344–1347.
Harari, Y. N. 2014. Sapiens. Israel: Harvill Secker.
Tomasello, M., 2009. The cultural origins of human cognition. Harvard university press.