Why the industrial revolution?
I've argued that the printing press, combined with a free market in books and the resulting spread of literate culture and the rise of national languages, gave Europe an institutional superiority over other cultures of that era that is now hard to fathom. As the term "literate culture" does not connote the radical shift in our very thought processes that occurred, I call this effect "book consciousness."
This led, in the first instance, to Western European conquest of the world's seas and colonization all over the planet -- a conquest that has been substantially reversed and could not be duplicated today because now most of the world shares book consciousness. It also led to a radical change in the way work skills were taught to children, which along with the scientific revolution and other fruits of the printing press led to the industrial revolution.
Clark's own data on wages and productivity can best be explained, I believe, by the radical changes in child investment strategy reflected in Protestant Reformation and a central aspect of book consciousness.
Finally, the industrial revolution occurred first in England rather than other parts of Western Europe due to the security advantages of being an island. Not at all coincidentally, England was by 1800 the leading colonial power. England was protected at low cost by its navies from most of the organized violence that ravaged the continent. This allowed it to develop a more secure regime of property rights, which in turn lowered the risks of the large capital outlays needed for industrialization. For a similar reason Japan initially outpaced its continental Asian rivals in industrialization.
Here's a link to the debate at Marginal Revolution.