When we fall prey to perfectionism, we think we’re honorably aspiring to be our very best, but often we’re really just setting ourselves up for failure, as perfection is impossible and its pursuit inevitably backfires. 
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Posted December 31, 2024 Reviewed by Lybi Ma
Big Brains
Primates have big brains, but so do elephants and whales. Elephants and whales, however, have much larger bodies that their brains monitor and control. Relative to each animal’s body size, primates’ brains are significantly larger than the brains of other animals.
According to the social brain hypothesis, primates have big brains because, unlike other animals, they have lived and thrived in socially bonded groups. Members of such groups cultivate relationships with one another through social grooming, watch out for one another, are wary of outsiders, and act jointly to protect the group. Success, both in and of such groups, requires that members track as many of the relationships between the individuals who make up their group as possible and that imposes a substantial computational burden that, as groups get larger, demands ever more brain power. A group of 10 has 45 dyadic relationships. A group of 100 has 4950, and a group of 150 has 11,175 possible dyadic relationships.
Dunbar’s Number
The Oxford University anthropologist, Robin Dunbar, discovered that primates’ brain sizes and, more specifically, the sizes of their neocortical areas correlate with their group sizes. The size of primates’ neocortical areas increases in direct proportion to each species’ group size. This results in what has come to be known as “Dunbar’s Number,” which is the number of individuals in a group that members of each species can manage computationally. Inserting the average neocortical size of our own species into the equation and capturing the correlation between primate neocortical and group sizes yields the Dunbar Number for Homo sapiens, which is 150.
Dunbar argues that it is not a coincidence that a host of human social patterns and arrangements typically involve between 100 and 200 individuals nor is it a coincidence that this is the typical size of hunter-gatherer communities, in which humans have lived for more than 95 percent of our species’ existence. According to all sorts of measures, individuals’ social networks, that is, the people with whom they might be said to have a personal relationship (as gauged by frequency of contacts, perceived emotional connection, and inclination to help), average around 150, even when they live in cities with millions.
This pattern reflects what is, in effect, a constraint on the number of relationships that human brains can keep track of. Dunbar notes that studies of everything from companies in modern armies (across nations), to medieval Alpine grazing associations, to villages in Norman England, to the friends that people list on Facebook, to networks of science co-authors, all show averages that fall within that range. Communities of this size rely on loyalties, friendships, and person-to-person connections to maintain order and tranquility and to solve disputes. Because of the limitations on our abilities to carry out these social computations, larger groups can no longer depend upon such direct, unceremonious means for controlling wayward or disruptive behaviors. Peer pressure will no longer suffice, consequently, they must invent explicit, formal devices to discourage such conduct. With substantially larger groups, the most conspicuous examples are the formulation of laws and the establishment of law enforcement.
The Problem with Big Churches
In his recent book, How Religion Evolved and Why It Endures, Dunbar explores, among other things, the implications of these lessons for religious communities. In large-scale societies the fractiousness both of major religions generally and of specific congregations is indisputable. Nowhere is this more obvious than in the United States, not because Americans are any more fractious than other people, but because of the relative openness and freedom of the American religious market.
Dunbar suggests that besides disputes about theology, morality, or leadership, one factor contributing to fissures in religious congregations is that many simply become too large. He proposes that the optimal congregation size is about 150, citing, for example, a study of more than 10,000 English parishes that found that weekly attendance at services topped out at about 175, regardless of the size of the overall community in which they were located. Dunbar notes that some religious groups have come to a similar conclusion. The Hutterites, for example, require congregations to spin off daughter congregations when numbers exceed 150.
Dunbar’s point is not that larger congregations cannot persist. But because of the limitations of humans’ social brains, without developing compensatory arrangements larger congregations will inevitably witness comparatively diminished identification and engagement among their members.
References
Bretherton, R. and Dunbar, R. (2020). Dunbar’s number goes to church: The social brain hypothesis as a third strand in the study of church growth. Archive for the Psychology of Religion 42, 63-76.
Dunbar, R. (1996). Grooming, Gossip, and the Evolution of Language. Cambridge: Harvard University Press.
Dunbar, R. (2022). How Religion Evolved and Why It Endures. Oxford: Oxford University Press.
Robert N. McCauley, Ph.D., is the author of Why Religion Is Natural and Science Is Not. He is a professor of philosophy at Emory University.
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When we fall prey to perfectionism, we think we’re honorably aspiring to be our very best, but often we’re really just setting ourselves up for failure, as perfection is impossible and its pursuit inevitably backfires.
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