I always thought of Dunbar's number as being closely related to our limits on vocabulary. Even though 150 is pretty small, you typically "know" somebody based

I always thought of Dunbar's number as being closely related to our limits on vocabulary. Even though 150 is pretty small, you typically "know" somebody based on how they relate to the others you know about, every permutation of who knows who, who likes who, who is similar to who and so forth. That number could be expressed as a power: 150^2 = ~22K. Most people have a vocabulary size of around 10k-30K words. It's probably a coincidence, but it's a number range that pops up a lot for medium/long term memory.