His thesis is radical - that the Industrial Revolution came about because the capitalist virtues of the upper and upper-middle class in England were passed on through families, and these families for a while out-bred the lower classes who were more susceptible to disease. But it doesn't depend on Darwinian evolution, Tim Worstall argues. It's not a triumph of genes as such; it's a triumph of transmitted and inherited culture:

We believe this about our society now: that attitudes, mindsets, extended networks, are indeed transmitted across the generations, not via Darwinian evolution, but in a way that can best be described as Lamarckian. The inheritance by the next generation of characteristics acquired by the previous one.

So we all already actually agree that Clark's mechanism is indeed a possible one (I personally regard it, now that's he's written the book to explain it, as obvious, but as I didn't see it before I read the book perhaps not that obvious.): all he needs to really prove is that the people who were transmitting the petit- and not so petit- bourgeois cultural values were indeed outbreeding those who didn't and the basic argument seems secure. Those bourgeois cultural values were indeed spreading through society via an evolutionary mechanism, just that of Lamarck, not Darwin.

JPod's remarkable aptitude - out of all those available - to succeed NPod as Commentary editor is explained by Lamarck not Darwin.