Before 1800 all societies, including England, were Malthusian. The average man or woman had 2 surviving children. Such societies were also Darwinian. Some reproductively successful groups produced more than 2 surviving children, increasing their share of the population, while other groups produced less, so that their share declined. But unusually in England, this selection for men was based on economic success from at least 1250, not success in violence as in some other pre-industrial societies. The richest male testators left twice as many children as the poorest. Consequently the modern population of the English is largely descended from the economic upper classes of the middle ages. At the same time, from 1150 to 1800 in England there are clear signs of changes in average economic preferences towards more "capitalist” attitudes. The highly capitalistic nature of English society by 1800 – individualism, low time preference rates, long work hours, high levels of human capital – may thus stem from the nature of the Darwinian struggle in a very stable agrarian society in the long run up to the Industrial Revolution. The triumph of capitalism in the modern world thus may lie as much in our genes as in ideology or rationality.
There is considerable evidence that commercially successful Englishmen had more kids than average, starting in medieval times. There is much less comparative evidence about other societies; do see pp.31-2, 55-7, but his best example concerns one Amazon tribe, where the warlike reproduced with greater frequency.
Of course the commercial revolution and then the so-called industrial revolution came out of England, not Germany or Italy. If it could be shown that the English family pattern stood out with regard to the rest of Europe, I would see greater heft in the idea. The Yanamamo differ in too many other regards for this comparison to illuminate any possible role for genetics in the European economic take-off. If family patterns can make the crucial difference, let’s keep as many other factors constant as possible. Otherwise I’m back to thinking it is institutions (most of all for science) and peer effects, not genetics, at the relevant margin of take-off. Did commercially active Germans and Italians, during the Renaissance, really fail to propagate their seed?
Addendum: See also the work of Oded Galor.