do we know about population and technological progress? A paper by Ashraf and Ga

http://www.nber.org/papers/w17037.pdfWhat do we know about population and technological progress?

A paper by Ashraf and Galorm http://www.nber.org/papers/w17037.pdf concludes: “…population density in pre-industrial times was on average higher at latitudinal bands closer to the equator.”

Yet the countries closer to the equator did not end up being the drivers of industrial progress, even though they sometimes had higher rates of progress in agricultural times. Northern Europe, with the exception of the Dutch Republic, was never the star for population density. This paper also indicates that technology drives population growth — more than vice versa — and that “time elapsed since a region’s neolithic breakthrough” predicts later technological progress fairly well.

If you add an extra baby to most societies, ceteris paribus, the rate of expected idea generation does indeed go up in theory. But how important a factor is that, compared to other influences on ideas generation?