Table 2.

Glossary of variables used

Variable	Description
xij	Quantitative phenotype of individual i in group j
wij	Fitness of individual i in group j
xj	Average phenotype in group j
wj	Average fitness in group j
	Average phenotype in the population
	Average fitness in the population
FST	= var(xj)/var(x), between-group to total phenotypic variance
CFST	FST calculated on cultural traits, variants, or beliefs
b	Group benefit from cooperative individual phenotype
c	Individual cost from cooperative individual phenotype
d	Synergistic effect from cooperative individual phenotype
m	Marginal effect of a group increase in A, xj, on an individual with trait A
n	Marginal effect of a group increase in A, xj, on an individual with trait B
ℓ	= m/(m − n), group frequency of trait A where the selection gradient reverses
φ	= n/(n − m) = 1 − ℓ
θ	= atan2(n, m), the polar angle of a line segment with slope n/m
k	Group frequency of trait A at which all individual fitnesses are equal
	Fitness for all individuals in group j at xj = k