Nature vs. nurture in global success?

In grad school, I read dozens of books and articles on the causes of the industrial revolution and economic success. Most focused on structural factors such as low taxes, open trade, etc. But some, such as Max Weber or Lawrence Harrison, have focused on culture (typically Protestant culture) as the primary driver of the economic success of nations.

Here's a recent variant of the "culture" argument, focusing on "middle class values" of hard work and thrift, separated from any particular Protestant ethos.

http://www.realclearpolitics.com/articles/2007/10/the_global_poverty_gap.html

Here's another discussion of the same book.

http://www.realclearpolitics.com/articles/2007/11/miracle_of_plenty.html