That is an older paper by the excellent Michael Kremer, worth keeping in mind, here is the abstract:
The nonrivalry of technology, as modeled in the endogenous growth literature, implies that high population spurs technological change. This paper constructs and empirically tests a model of long-run world population growth combining this implication with the Malthusian assumption that technology limits population. The model predicts that over most of history, the growth rate of population will be proportional to its level. Empirical tests support this prediction and show that historically, among societies with no possibility for technological contact, those with larger initial populations have had faster technological change and population growth.
This bears on my earlier Bloomberg column, today cited by Mike Lee, suggesting that having more children is likely to help out on the climate change issue.