The heritability of fertility makes world population stabilization unlikely

So far the consesus was that migrants from traditonally child rich societies, acclimated already a generation later at local lower levels if prosperitiy and education level was reached as well. So it's the economy and social stability through the state that replaces children as the only "pension and care" provider for retirement.

FRANCE: "We show a convergence towards French standards that differs across groups of origin. Women of Southeast Asian descent deviate from the fertility pattern of their parents, while those of Turkish descent preserve their parents’ cultural heritage. These different paths of adaptation between groups partly reflect cultural distance between parents’ country and host country. They also depend on family social capital, family structure, and family values. Access to a higher level of education is a crucial factor in erasing differences between groups" https://hal.archives-ouvertes.fr/hal-02081758/document

Population didn’t stabilise, anywhere, ever. Nothing “worked” for Europe. Most of Eastern Europe is losing population to emigration. If you look at breeding populations rather than geographies you see some populations growing and others shrinking. You don’t see steady states.

The population behaviour of the British and that of descendants of those resident in Britain in 1900 are not the same thing. Focusing on nations obscures that fact.

This is ridiculous.

The replacement fertility rate to maintain population before modern medicine could be closer to ten than two not so long ago.

War, famine, disease, accidents, and infant mortality made it so surviving until you were old enough to start having your own children was rare and women were often pregnant or nursing continuously as long as they were fertile.

The premise of heritable fertility driving population and reproduction rates in humans is really far off. We're not having litters of kittens.

If it were true fertility rates could not possibly have dropped so far in so few generations after modern medicine and the insane reduction in violent death rates seen in the last thousand years.

Yes this seems to miss actual examples of developed countries where fertility is approaching and dropping below replacement rate.

> 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.

Poverty and risk, fertility changes lag behind medical advances / availability e.g. in europe the large families were mostly around the first half of the 20th century (to soon after WWII), where culturally you wanted to have a fair number of children so you'd have some living to adult age (and also manpower on the farm) but medicine had also progressed and spread enough that almost all of them would survive to adult age.

Culture quickly caught up and the default assumption that all children will live to adult age means even farming families aren't really large anymore (not to mention machines & automation makes the manpower of many children less relevant).

Developed countries are mostly at the point where medical advances are getting available, leading to huge families because the cultural aspect hasn't caught up yet.