The famous 150 friends is a very shaky number.
Robin Dunbar extrapolated from brain size and group size across 38 primate genera to about 150 stable human relationships. In 2021 Lindenfors and colleagues redid the analysis with newer data and got 16 to 109 – with confidence intervals spanning 2 to 520.
Useful: When a round number comes from an extrapolation, ask for the confidence interval.
Source: en.wikipedia.org