Dunbar's number: your brain can hold 150 relationships. Your database has more
Anthropologist Robin Dunbar calculated how many stable relationships a human brain can maintain: about 150. What to do when your business has five times that.
In the 1990s, the British anthropologist Robin Dunbar noticed a correlation between the size of primates' neocortex and the size of their social groups. Extrapolated to humans, it produced a number around 150 — roughly how many stable relationships a human brain can realistically maintain. Villages, army companies, parishes: historical communities cluster around that number suspiciously often.
Layers of closeness
Dunbar later described those 150 not as one pile but as concentric circles: roughly 5 closest, 15 good friends, 50 friends, 150 meaningful acquaintances. Each layer needs a different contact frequency to stay warm — and a relationship left untended quietly slips down a layer. It doesn't disappear at once. It just fades.
Business lives beyond the number
Now the sales reality: an active salesperson meets hundreds of people a year, and a small company's database climbs past Dunbar's number within its first year. That's not a reproach to anyone's memory — it's a biological limit. Beyond 150, the brain can't maintain the relationships. A prosthesis has to: an address book, notes, a system that keeps the layers for you.
The prosthesis doesn't run the relationship. It holds it
An important piece of honesty: no tool creates a relationship. The phone call, the interest, the kept promise — that's still human work, and software won't do it for you. What a tool can do is keep five hundred relationships “conscious”: who's in which layer, when you last spoke, what was promised, when it's time to reach out. The brain then does the one thing only it can — talk to a person, not to a list.
What to take away
Don't try to remember more people. Decide which hundred and fifty or so you want to keep close — and for everyone else, build a system that brings you back into the game at the right moment. Dunbar didn't describe a weakness. He wrote the spec.
Lemnio is built precisely for the relationships beyond Dunbar's number — it holds the history and the dates so you can hold the conversation. Start free.