Cooperation (to appear in open access textbook Evolution, Culture, and Human Behaviour)

When people consider what it is that makes humans unique, they are likely to come up with a range of characteristics such as walking around on two legs, having big brains, our language and culture (van Straalen, 2018). Famously, Desmond Morris in his book, The Naked Ape (Morris, 1967), concluded that humans’ most obviously striking trait compared to other mammals is our hairlessness! But arguably the most vital of our unique traits is our unusually strong willingness to cooperate, often in notably large numbers. As a result of the importance and prevalence of [[cooperation]] to the human species, some go so far as to call humans ultrasocial (Campbell, 1983). It is likely this ultra-cooperativeness helped humans to both survive the challenges of the African savannah, where our species evolved, and then our rapid expansion across the globe (Townsend et al., 2023).However, despite this clear benefit to human success, it is all too common for discussions of cooperation to begin by calling it a puzzle (e.g., Henrich & Muthukrishna, 2021) or a problem (e.g., West et al., 2011). It is the case that [[natural selection]] is generally a process of [[competition]] between individuals, and a trait that reduces an individual’s chances to reproduce will be selected against. Cooperation seems costly to reproductive fitness and often benefits other individuals, so surely it is selected against? This is the source of the notion of cooperation as a puzzle. Yet in the evolutionary sciences there has been a lot of work undertaken to understand how behaviours that appear to undermine the fitness of cooperators could have evolved. In this chapter, we will explore the various approaches that human evolutionary scientists have developed to understand cooperation as a trait and to account for how humans can be as cooperative as we are.