Bad title. Cool article.
Doesn't the article directly contradict this statement? What am I not understanding?Similarly, there is no clean relationship between the amount of folding and the number of neurons, the total area of the cortex, or the thickness of the cortex.
I think the statement means that there isn't a 1:1 correspondence between the amount of folding and the other things listed. The relationship only exists when you consider two independent variables, not one. The sentence is very awkwardly written, however.
This article seems promising. It looks like it's mostly about the mechanics and less about how genetics & development are involved though. Wish I could be more helpful but I'm not in this field...
Mechanics is one way to explain it. I was imagining the folds developed as a result of some sections being initially more rigid than others, and the outer portions of the folds grew away from the rigid regions. But it also makes sense that there would be a pulling force of sorts to move / hold the inner sections closer to the center of the brain...