First, I’ll steal Jason’s summary of the book’s thesis:
Clark’s A Farewell to Alms argues that the Industrial Revolution took place in Britain circa 1800 because at that time and place, the middling to lower classes had attained sufficient breeding to make it happen. The Industrial Revolution was the product not of institutions, but of sufficiently widespread personal habits and values . . .
He presents evidence for an important, little-discussed demographic trend, and I think he’s likely right about it, at least in the broad outlines: During the era of largely subsistence agriculture, only the upper classes produced a population surplus. The lower classes tended not quite to replace themselves — so the children of upper-class parents could expect to slide down the social scale, while the children of lower-class parents could expect either to hold steady (in good times) or to die (in bad ones). As time went on, more and more people would have upper-class ancestry, and with it, upper-class breeding. In time there came the Industrial Revolution, in which upper-class habits and values, or possibly upper-class genes, did the heavy lifting.
Jason suggests that a critical mass of impoverished nobles couldn’t produce the Industrial Revolution because aristocratic norms are antithetical to the norms of commercial, industrialized societies. I find this eminently plausible, but what if Clark is arguing for inherited, or biological, intelligence? Clark is fairly ambiguous on this point – are aristocratic families transmitting learned customs or innate smarts to their poorer, more numerous offspring? – but his formulation implies some hereditary component to intelligence.
If Clark’s thesis hinged on the spread of upper-class social norms, the seamless transition from clerics and warriors to merchants and industrialists would be less plausible. But if intelligence is largely or partly heritable, it might explain why the gulf between aristocratic and bourgeois values didn’t derail the Industrial Revolution. Presumably, the same smarts that made a medieval aristocrat successful at warfare or diplomacy were passed on to his remote descendants, who then became engineers or captains of industry.
I can still think of several problems with Clark’s thesis. For one, were medieval aristocrats really England’s “best and brightest?” Or were they descended from a band of unscrupulous freebooters who happened to fight for the winning political dynasty? I’m also not sure why other top-heavy feudal societies didn’t reach the population tipping point before England (to be fair, I haven’t gotten to that part of the book yet). But if you buy certain ideas about the heritability of intelligence, Clark offers a pretty plausible explanation for the origins of the Industrial Revolution.