tycho wrote:Why is it so?
The population growth of any organism adapts to the potential carrying capacity of its environment. The South Asia region (especially the river valleys and deltas) has the best soils, water, stable weather etc, translating to a high natural carrying capacity for life. Human beings in this region don't need to spend as much effort in transforming their environment for survival or propagation.
Other regions of the world require high human effort to convert to optimum conditions for human numbers. This required energy pre-investment takes away from peoples reproductive potential.
"The opposite of a correct statement is a false statement. But the opposite of a profound truth may well be another profound truth." (Niels Bohr)