What happened
Big swings and turning points, with their causes. Click a line to jump to that year.
Event log
Culture over time
Every rule change, with how it happened: drift, imitation of a more successful neighbour, fission, or the threat-driven rise and peace-driven decay of ritual.
Sweep
Round robin of the societies you tick, plus the two custom ones above. Each pair runs N seeds; survival counts a founder as alive if it or any daughter band is alive at the end.
Ranking
Pairings
The model
Every person is an agent with a mother, a father, skills and a cause of death. One tick is one year. Each society carries a genome of rules — marriage, mate choice, descent, residence, labour, sharing, foraging, trade, governance, norm enforcement, outgroup stance, captives, famine policy, fission size and ritual — and the rules change only what they mechanically change.
Each year
- Climate and shocks. A good, normal or bad year; rare forest fires, storms and epidemics.
- Forage. Workers pick plant, game or fish patches within range of camp by expected return. Hunting is high-variance. Patches deplete and regrow logistically, so carrying capacity emerges rather than being set. Camps move toward richer ground.
- Share. Food flows by the sharing gene (household, lineage, camp, or ruler with an elite cut), with some demand-sharing between groups. Pooling invites free-riding unless norms are enforced.
- Live and die. Forager-calibrated hazards (≈18% infant mortality, ≈60% reach 15) for infant illness, infection, accident, other illness and old age, amplified by hunger and reduced by medicine. Fathers, grandmothers and residence rules change child survival.
- Pair and give birth. Marriage rules, incest avoidance, polygyny by status, intermarriage across societies, birth spacing, maternal death, famine infanticide.
- Conflict. Raids decided by governance from hunger, grievance, unpaired men, relative strength and the leader's temperament. Captives are killed, ransomed, enslaved or adopted. A crushing win can conquer a weakened rival.
- Trade. Peaceful neighbours trade: a yield bonus, famine relief, technology diffusion — and disease.
- Know-how. Skill is per person and taught to children; a society's level is its best few practitioners. Fifteen technologies (including six medicines) are invented, diffused and lost when experts die.
- Culture evolves. Rare drift, imitation of a visibly more successful neighbour, conquest, and fission into daughter bands with a mutated genome.
Sources the mechanics lean on
- Read (2003), multi-agent !Kung demography — birth spacing and marriage rules set population.
- JASSS (2017), minimum viable hunter-gatherer populations — restrictive marriage hurts small groups.
- SFI working paper 2017-12-037, the polygyny puzzle; Francesconi, Ghiglino & Perry, an evolutionary theory of monogamy.
- Turchin & Gavrilets; Turchin et al. (2013) — war as cultural multilevel selection.
- Epstein & Axtell, Sugarscape; Janssen (2009), Artificial Anasazi — carrying capacity dominates.
- Gurven & Kaplan (2007) life tables (approximate baselines; every parameter is in
src/params.js).