Dr Gregory Clark of the University of California has come up with an eye-catching explantion for British industrialisation after 1800. Unlike most other historians − who tend to suspect that the role of institutional factors was crucial, but can't prove it − Clark reckons that it was in fact downward mobility that, through means of either genetic or cultural transmission, permitted a repertoir of skills and dispositions (the middle class mentality no less ) to spread through the population.
Up until around 1800 the Malthusian trap prevented anything like real affluence. Even the wealthiest members of early-modern society consumed about the same daily quantity of calories in their diet as primitive hunter-gatherers.This was because all gains in productive capacity through technological progress were offset by the population growth they encouraged. (See my recent post on Fair Trade for how the global market for coffee is locked in the same sort of feedback loop).
Clark has trawled through the records and found that during the few centuries leading up to the Industrial Revolution the rich had many more surviving children than the poor. "The modern population of the English is largely descended from the economic upper classes of the Middle Ages," he therefore concludes.
So, the people that had found the behavioural path to riches − an inclination to hard work, literacy and deferred consumption plus a disinclination to resolve disputes with violence − bequeathed these dispositions to the general population as their offspring slid down the social ladder to fill the gaps in the ranks of the lower orders.
When Clark checked the birth records in countries like Japan and China that notably failed to industrialise at this time, he discovered a comparative lack of fertility in their social elites.
This theory does of course have all sorts of striking non-PC implications that the NYT article I discovered it in neglected to expand on. i.e. can we not then blame the increase in laziness, violence, ignorance and undeferred consumption to the upward mobility experienced by meritocratic societies driven by liberal economic policies? And what happens when the industrialised world accepts mass immigration from developing nations where midde-class values are typically surrounded by hostile forces like Custer at Little Big Horn? etc.
The theory is however probably falsifiable on several levels that could be explored even by those historians not wedded to purely institutional explanations. For instance, we know that the Black Death took out approximately 50% of the English population. Surely this event reversed the flow of social mobilty, as we know for certain that it dramatically readjusted economic relations in our country in favour of the labourer.