All of my grandparents come from big families. My grandmother on my father's side comes from a family of 12 children.
Yet my grandmother only had 4 children and my father only 2, and now I only have 1.
This is an anecdote, but I don't think heritabiliy has anything to do with it.
Large families simply happen due to poverty. When poor, you want more children because there's strength in numbers. Plus the women are staying home and can afford to have children.
Nowadays access to contraceptives is common and in Europe for example it's not feasible to have a lot of children due to costs (property, education, women having to eventually quit their job, etc).
Anyway, I think the evolution of poverty is a much greater predictor of population growth than anything else.
Yet my grandmother only had 4 children and my father only 2, and now I only have 1.
This is an anecdote, but I don't think heritabiliy has anything to do with it.
Large families simply happen due to poverty. When poor, you want more children because there's strength in numbers. Plus the women are staying home and can afford to have children.
Nowadays access to contraceptives is common and in Europe for example it's not feasible to have a lot of children due to costs (property, education, women having to eventually quit their job, etc).
Anyway, I think the evolution of poverty is a much greater predictor of population growth than anything else.