= concept and article
= "our capacity to cooperate in societies of millions of genetically unrelated individuals". 
"Cultural-evolutionists have produced a large literature on what is sometimes called the “problem of human ultra-sociality“. Its main theme was popularised in a book by Paul Seabright: from an evolutionary point of view, how was it possible for the human species to go from living in small foraging bands of close relatives in the Palaeolithic to the global network of billions of anonymously interacting strangers that we see today?
Modern societies engage in incredibly complex and incredibly large-scale forms of cooperative behaviour, with almost infinitesimal divisions of labour connected in a delicate skein of confidence and trust. Think of what it takes to get the New York Stock Exchange humming along, or the frightening amount of organisation and solidarity it took to wage the Second World War (on either side). Or, as Peter Turchin wondered, why did so many millions enthusiastically volunteer to risk death for unrelated strangers in the Great War?
I think this is a good summary of the cultural-evolutionists’ view on ‘ultra-sociality’ overall: humans have an instinct for cooperation, but the social norms of fairness evolve gradually to accomodate a wider definition of ‘insiders’ as a society gets larger and more complex.
But a related puzzle gets lost in the shuffle: why does ‘ultra-sociality’ vary so much across the world? Why are pro-social institutions not more widespread? The poorest countries like Afghanistan have pretty low levels of “social capability” in governance, to put it mildly. Why does the South of Italy have so little “civic capital” compared with the North of Italy ? Why aren’t most countries like Denmark?" (https://evonomics.com/pro-social-institutions-come/)
* Article: Human ultrasociality and the invisible hand: foundational developments in evolutionary science alter a foundational concept in economics. By David Sloan Wilson and John M. Gowdy. Journal of Bioeconomics, April 2015, Volume 17, Issue 1, pp 37–52|
"Advances in the study of social behavior require a revision in the economic concept of the invisible hand, which states that self-interested behavior leads to well-functioning societies without individuals having the welfare of the society in mind. Evolutionary theory shows that self-interest does not robustly benefit the common good because behaviors that are “for the good of the group” seldom maximize relative fitness within the group. The evolution of group-level functional organization requires a process of group-level selection. Species that have become highly adaptive at the group level are called ultrasocial. The idea that an invisible hand leads to social harmony is valid primarily for ultrasocial species, where selection at the group level results in individual-level behaviors that produce group-beneficial outcomes. Individuals do not necessarily have the welfare of the group in mind, but neither do their behaviors or underlying proximate mechanisms resemble the economic concept of self-interest. Evolutionary science therefore provides a valid concept of the invisible hand, but one that is different from the received version, with far-reaching implications for economics, politics, and public policy."
- Gowdy, J., & Krall, L. (2013). Ultrasociality and the origin of the Anthropocene. Ecological Economics, 95, 137–147.
- Gowdy, J., & Krall, L. (2014). Agriculture and the evolution of human ultrasociality. Journal of Bioeconomics, 16(2), 179–202.