>>17870149 (OP)>What created this divide /his/?Weather.
Rice does really well in warm, wet, climates, so well in fact that in some places you can harvest a rice crop 2-3 times a year, especially so if it's cultivated in a flooded paddy. Rice is also the definitive, "more people = more food" cereal since as laborious as it is to grow (according to google the first rice planting machine wasn't invented until 1898 in Japan) every person, and every additional bit of land, devoted to rice cultivation brings back exponential returns in a way you don't see out of other cereals. This is why you go into some of these Southeast Asian countries and they'll have nearly every square inch of land converted into a paddy and how you can start figuring out why places like China, Indonesia, and India, have most of our species.
Wheat on the other hand likes drier, colder, temperate climates and even in the best conditions you'll only get a 2 harvests from it. Wheat makes up for these short comings by having significantly more dietary protein and require much less labor - 1 person can theoretically grow enough wheat, all by themselves, to feed somewhere between 14-32 people.
>>17870160Everything in history is dictated by agriculture/food production.