#48: Robin Dunbar - Friends, Tribes and Social Cohesion

Episode Summary

Renowned evolutionary psychologist Robin Dunbar returns for part two of his conversation with Jef Szi and the How Humans Work Podcast, diving deeper into the limits and leaps of human social patterns.

In this episode, Professor Dunbar expands on the evolutionary foundations of human relationships, moving beyond social grooming and the endorphin system to explore kinship and the deeper nature of our social lives.

He begins by examining the cost and time investment required to maintain our inner circle of intimate friends. From there, he maps out the concentric layers of more peripheral friendships and the behaviors and expectations that characterize them. Dunbar emphasizes the vital role our closest five friends play in our wellbeing and longevity.

We then explore how humans scaled up from the group sizes typical of primates to the now-famous “Dunbar’s Number” of 150. This leap—central to the Social Brain Hypothesis—reveals how brain size in primates correlates with social group size, due to the cognitive demands of managing complex, stable relationships.

Dunbar illustrates these ideas through compelling examples—courtship, language, and religion—showing how humans have creatively repurposed existing biological mechanisms to sustain cohesion in increasingly larger groups.

He also sheds light on how cultural practices like laughter, feasting, ritual, and storytelling serve to bind people together into broad, loosely connected “supergroups.”

Ultimately, Dunbar offers a concentric model of our social world, illuminating the patterns, breakthroughs, and constraints of human sociality. This conversation helps us better understand our evolutionary journey and how we might draw on both embodied emotion and cognitive insight to navigate a highly uncertain future.

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About: Robin Dunbar: Robin Dunbar is Emeritus Professor of Evolutionary Psychology at Oxford University. His work in the Experimental Psychology department at the Magdalen College is concerned with ‘trying to understand the behavioral, cognitive and neuroendocrinological mechanisms that underpin social bonding in primates (in general) and humans (in particular).’ Robin is the author of several books, including The Social Brain, Human Evolution, and Friends: Understanding the Power of Our Most Important Relationships. Professor Dunbar is known for advancing the Social Brain Hypothesis with Dunbar’s Number.

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Episode #48 Takeaways

• Dunbar's number suggests humans can maintain 150 relationships.
• Time investment is key to strong friendships.
• Friendships provide emotional support during crises.
• Social interactions can be as beneficial as medical interventions.
• Volunteering can substitute for friendships in terms of social exposure.
• Cohesion in larger groups requires superficial cues and shared knowledge. Friendship layers are assessed within the first four weeks.
• Common interests determine the depth of friendships.
• Intuition plays a key role in evaluating relationships.
• Institutions help manage social cohesion and relationships.
• Shared knowledge and folklore create larger communities.
• Religion serves as a stabilizing force in communities.
• Top-down structures provide discipline, while bottom-up structures foster local identity.
• Population density poses significant future challenges.
• Humans have historically found solutions to problems.
• Optimism is essential for...