Dunbar's Number
your brain caps real relationships around 150 — stop pretending it doesn't
Grounded in the research on Wikipedia: Dunbar's number; Robin Dunbar, 'Coevolution of neocortical size, group size and language in humans' (1993)
the setup
Dunbar's number is the rough ceiling on how many stable relationships you can actually maintain — the people you'd know how to behave around at a party, who you'd call a friend without lying. The famous figure is about 150. Not 150 contacts. 150 people you have a real, two-way relationship with. Everyone beyond that is a face, a name, a follower count. Your brain literally can't track more.
the mechanism
Anthropologist Robin Dunbar pitched this in 1993 by correlating primate neocortex size with group size, then extrapolating to humans. Bigger social brain, bigger tribe you can mentally model. He pinned the human estimate near 150 and backed it with stuff like Neolithic village sizes and military company size. Heads up: it's a contested estimate, not a law. Some 2021 replications couldn't pin a number at all. Treat 150 as a vibe, not a formula.