Taking the year at which TFR dipped well below 4 children per woman (say, below 3.8 to set a number) is not the perfect, but a good way of telling since when this process started. Why that number? 4 or a bit less than that was the lowest TFRs typically shown in Hajnal-Europe well below the demographic transition, so it is the lowest number attainable in a pre-industrial setting without having the population dying out.
France dipped below that number in the late 1830s, Switzerland in the mid 1880s and all the rest of core Europe (Germany, UK, Netherlands, the Nordics etc.) and their offshoots (US, Canada, Australia, NZ) between 1890 and the onset of WWI. France is two generations ahead of everyone else in that game, playing in its own category.
All valid, excellent points. The UK was still a bit in front of Germany, though I agree that it’s really France that stands out.
Fertility rates in UK, Germany, France 1800-2015.
There’s a huge variety of other factors to consider, for instance:
1. Starting genotypic fertility preferences (e.g. during the medieval age and earlier). I suspect they would fit along the standard r/K racial continuum proposed by Rushton for the races of mankind – that is, Negroids > Caucasoids > Mongoloids. Intraracial group differences are even more speculative, but still possible!
2. Pre-19th century trends. E.g., the UK hovered at around 4 children per woman during the 17th century. Then it increased to an average of 5 children during the 18th and first half of the 19th century.
3. Selection for breeder genes should be become exponentially, not linearly, more powerful as TFR falls. Example: If say a “breeder” has 2 children more on average than a normie, then in a population with a TFR of 5 – that is, as in many European polities before the demographic transition – (s)he’d have 7 children, which is not that a big of a difference relative to the average (and may not even make an impact at all if those 2 extra ones die off before themselves reaching reproductive age because higher fertility preferences are correlated with lower IQ, greater risk of poverty, etc., which are maladaptive in very poor economies); whereas in a society with a TFR of 1 – such as modern South Korea – (s)he’d have 3 children, and will make a disproportionate contribution to the gene pool.
Consequently, while breeder genes may have been relatively more competitive in 19th century France than in Germany, the latter may well have substantially caught up by the very dint of its post-1970 fertility collapse.
4. Selection for breeder genes is stronger in wealthier (slightly post-Malthusian) societies. The UK was much more wealthy than Europe since the Glorious Revolution, and substantially higher than average for approximately a millennium. You can look at Angus Maddison’s statistics, or if you have a literary inclination, you can read the travels of Arthur Young in France on the eve of their Revolution to get a sense of those differences, which were already very substantial even before the Industrial Revolution had gotten going (e.g. meat roasts were standard fare in England, a luxury in France; many French peasants could not afford to heat their dwellings, and thus had to stay in bed during the mornings instead of being productive). Real incomes in England were approximately double those of France.
Why is this important? Because “overbreeding” may well have incurred fewer costs in the richer UK than in a country like France, where people had much narrower margins for survival, especially during times of dearth. France experienced regular famines throughout the Early Medieval period up to 1794-95, whereas the United Kingdom did not really even have any truly severe famines after the Black Death (excepting the Irish Potato Famine).
This may well have annulled the relative genetic advantage French breeders enjoyed over their English counterparts due to France’s lower average fertility rate from the early 18th century.
This effect certainly played itself out in extra-European settled territories such as the United States, where the average colonist enjoyed access to vast tracts of land. With no famines or even periods of dearth to keep the breeders in check, it’s plausible that breeder genes enjoyed much more success there than in Europe. Indeed, despite early modernization, the US has consistently maintained significantly higher fertility rates than developed European nations throughout the 20th century, at least until recently. And this is despite childrearing being cheaper and more convenient in the welfare states of Western Europe from the 1960s/70s on. Regionally, based on these hypotheses, we can also expect that breeder genes would be least prevalent in New England (function of earliest settlement + cultura-mandated, ultra-high Puritan fertility, which would have constrained the relative competitiveness of breeders) and greatest in the newest colonized territories (see Jayman’s Pioneer Hypothesis). This is indeed what we see today.
Indeed, what we generally see today in Europe is that TFR is highest in historically rich regions – the UK, the Netherlands (though their period of preindustrial per capita surplus happened in the 17th century, not the 18th-19th) – as well as in France (not particularly rich historically, but did see a very early demographic transition). All factors that we can expect to be associated with the spread of breeder genes.
I accept that this theory, though tantalizing, is pretty flimsy and has no hard evidence in its support. Hopefully somebody can do a GWAS for fertility preferences before the idiocracy takes over.