JaredDiamond points out several geographical constraints (or ultimate) causes for Eurasian development compared to African, Australian and American.
- Overall size influences population size. (Clearly more land supports more people.) And more people = more creativity.
- Overall size also influences the number of species of plants and animals, producing more candidates for domestication.
- East / West axis rather than North / South axis. Domesticated plants and animals travel more easily East / West because climate remains the same at same latitude. On North / South continents, much harder, because to the climatic zones are very different; including some dramatic step-changes such as whether it rains in summer or winter! Plants adapted to one won't grow in the other.
- Zones which are difficult for agricultural techniques to peculate through such as deserts and thick forests.
- On the other hand, he thinks ultimately Europe had a geographic advantage over China because of environmental barriers. Mountain ranges, but lack of unifying rivers, fragmented Europe politically, which preserved cultural diversity. In essence, this acted like a CompetitiveArchitecture. If one country rejected a particular technical or cultural advance, then another might adopt it and thrive. Contrast China, which had a lot of technical innovations (due to large population and successful agriculture) but turned away from them for political reasons. (See also HappyMedium)