From the article: In fact, from a pure Darwinian perspective of fitter organisms producing more offspring, the opposite is happening with modern Homo sapiens. Impoverished, less healthy, and thus typically shorter families tend to have more children than prosperous families.

Everybody knows it, but it's pretty crazy when you think about it. However with a generally increasing standard of living that factor should still get smaller and smaller and the people thus taller and taller.