We carry more contacts than almost any generation before us. A phone holds a thousand numbers. A feed follows tens of thousands of people.

Everything about modern life whispers that connection is limitless.

Yet ask most people how many others they could call at three in the morning in a real emergency, and the honest answer is probably a handful. That gap, between the crowd we can reach and the few who actually count, is what one of the most quoted ideas in social science tries to explain.

A quick note on what this is and isn’t. I am not a psychologist, neuroscientist, or anthropologist, and none of this is advice about your own relationships. It’s a reader’s walk through a contested body of research. The experts themselves argue over it, so treat it as a lens for thinking, not a rule for living.

What the theory actually says

The idea is usually called Dunbar’s number, after the British anthropologist Robin Dunbar, who proposed it in the early 1990s. Studying primates, he noticed a pattern: the bigger a species’ neocortex (the outer, thinking layer of the brain), the bigger the social group that species tended to live in. Dunbar’s foundational paper plotted the human brain onto that pattern and predicted a natural group size of roughly 150.

The figure his math actually produced was 147.8, conventionally rounded to 150. What matters is what he meant by a relationship. Not just a name you recognize, but a person you know well enough to place within your wider web: how they fit with everyone else who matters to you.

He also described the 150 as the outer ring of a set of nested circles, each about three times bigger than the one inside it. When MacCarron, Kaski and Dunbar studied mobile phone call records, they found people’s networks arranged in layers of about 5, 15, 50 and 150. The innermost five are the people you lean on hardest. As Dunbar puts it, “My research suggests we can only maintain five intimate friendships – but we know the names of up to 1,500 people.”

Why the number stuck

Part of the appeal is that 150 kept turning up in places nobody planned. It seemed to echo the typical size of traditional villages, the strength of basic military units, and the size of companies before they need formal hierarchy to hold together. When a figure derived from monkey brains lines up with how humans have organized themselves for centuries, it travels far beyond the journals and into business books and casual conversation.

Perhaps the deeper reason it stuck is that it flatters something we already suspect. Most of us feel, without being told, that our attention for other people runs out well before our contact list does. Dunbar’s number gave that private hunch a tidy explanation and a memorable figure. The trouble with tidy figures is that they invite scrutiny.

The challenge to the number

In 2021, a team at Stockholm University, Patrik Lindenfors, Andreas Wartel and Johan Lind, went back to the primate data and ran the analysis again with newer methods. Their reanalysis did not produce a clean 150. Depending on the method, they got average group sizes of roughly 69 to 109, and 16 to 42. The range of possible values was so wide, one span ran from 4 to 520, that the authors argued no single reliable number could honestly be pulled out at all.

Lindenfors put it bluntly. “The theoretical foundation of Dunbar’s number is shaky,” he said. He also questioned the whole leap from monkeys to people. Other primates’ brains, in his words, “do not handle information exactly as human brains do, and primate sociality is primarily explained by other factors than the brain, such as what they eat and who their predators are.”

His colleague Johan Lind went further, suggesting the ceiling may not be fixed at all. Lind proposed that “just like someone can learn to remember an enormous number of decimals in the number pi, our brain can be trained in having more social contacts.”

Dunbar did not accept any of this quietly. He countered that “the study used flawed statistical methods and fails to account for the body of evidence we now have to support Dunbar’s number.” His rebuttal came down to a fight over which statistical method the analysis should have used. On the same data, he wrote, “the LSR method used by the Stockholm study predicts 71 (the basis of their claim), whereas the RMA method I originally used predicts 158.” The Stockholm team defends its choice. Dunbar defends his. That is roughly where the argument still sits.

What the dispute is really about

Strip away the statistics and something interesting survives. The two sides disagree about the exact number, and about how much the monkey data can tell us about people.

But even the harshest critique doesn’t claim we can each maintain ten thousand real friendships. It claims we can’t say the ceiling is exactly 150, and that with effort it might sit higher than Dunbar allows.

My read, as an observer with no stake in the statistical fight, is that the exact figure was always the least durable part of the idea. Whether the honest number is 42, or 150, or somewhere in the roughly 100-to-230 range of Dunbar’s own confidence limits, the practical point barely moves. There’s a budget, it’s likely smaller than your contact list, and it gets spent whether or not you notice where it goes.

So the more useful question isn’t how many friends the brain permits but who you’d want inside the smallest circle if the number really is that tight — and that’s a question you can answer without waiting for the researchers to settle where the ceiling sits.

If reading about limited connection stirs something heavier, a sense of isolation you’ve been carrying quietly, it’s worth talking to a qualified counsellor or therapist. That’s a conversation worth having with a person, not a phone.