The difference between the obvious Inuit form of cultural evolution and the non-obvious marriage form is that of within-culture versus between-cultures evolution.
Consider: one Inuit tries the red berries and discovers they make her sick.
Without any deliberate effort, the Inuit ended out with a remarkably effective set of survival techniques.
Something like this seems so obviously true as to not require further discussion.
Suppose that one of my children gets a mutation causing 1% less risk of infectious disease.How much advantage can an individual cultural trait confer? Compare Judeo-Christian attitudes about sex to Greco-Roman attitudes about sex.One might argue that the Judeo-Christian attitudes are superior, since Christianity did eventually take over Rome.This is fine, but they might get killed in a car accident before their tenth birthday, or be too ugly to find a partner, or get an infectious disease anyway because 1% less risk isn’t really much less risk.If my child survives, and passes her mutation on to millions of other people all with their randomly distributed level of other good and bad genes and good and bad luck, then maybe eventually over thousands of generations, people with the new beneficial mutation will take over from people without it.This is sort of group selectionism, but in this case I’m okay with it. Becoming cancerous makes a cell much more likely to spread within its organism – the equivalent of positive intracultural selection – but also makes its organism at a severe disadvantage compared to other organisms – the equivalent of negative intercultural selection.