Cooperation and collective brains

Four dot models from Joseph Henrich's account of cultural evolution. Each one turns a single idea into something you can run: who meets whom, what people copy, and how groups, towns and connections shape cooperation and invention.

Toy models: the dots are simulated, never data. Inputs on the Whatcom map are measured.
Clusters of green cooperators beside the beta greater than c over b card

Cooperation evolves when phenotypes assort

Pairs meet, cooperators pay c to give b, and cooperation spreads exactly when β clears c/b.

/assortment
Nine groups of dots, most turned green, with the CFst equation

Groups make the assortment cooperation needs

Conformity, copying and group competition build cultural CFst, the β that lets cooperation hold.

/assortment/groups
Five linked towns climbing in skill while a cut-off town fades

Big, linked, diverse groups ratchet their skills up

The collective brain: copying, recombining and inventing, with the Tasmania effect when a town is cut off.

/collective-brain
Whatcom County map with commuting flows along the roads

Whatcom's towns as cultural groups

The groups model on 19 real towns, with LODES commuting along the roads and four levers to place.

/bellingham/assortment, behind the Bellingham passphrase

Sources: Henrich (2004, American Antiquity) and Muthukrishna and Henrich (2016, Phil Trans R Soc B) for the collective brain; Fletcher and Doebeli (2009) for the assortment rule; Bell, Richerson and McElreath (2009, PNAS) for cultural Fst; Handley and Mathew (2020, Nature Communications) and Muthukrishna et al. (2020, Psychological Science) for measured values, about 0.01 between US regions.