the practical consequence of the conditions obtaining in Darwin’s primal horde must be exogamy for the young males… ‘No sexual relations within the totem.’
Freud derives exogamy as a necessary social consequence of the primal horde’s dynamics, tracing it from biological necessity to conscious law to totemic prohibition, while noting the unresolved question of whether exogamy preceded or was derived from totemism.
, Totem and Taboo, 1913thesis