(Extracted from Atomic Habits by James Clear)
The primary axis of the Americas runs from north to south. That is, the landmass of North and South America tends to be tall and thin rather than wide and fat. The same is generally true for Africa. Meanwhile, the landmass that makes up Europe, Asia, and the Middle East is the opposite. This massive stretch of land tends to be more east-west in shape. According to Diamond, this difference in shape played a significant role in the spread of agriculture over the centuries.
… By comparison, the climate varies greatly when traveling from north to south. Just imagine how different the weather is in Florida compared to Canada. You can be the most talented farmer in the world, but it won’t help you grow Florida oranges in the Canadian winter. Snow is a poor substitute for soil. In order to spread crops along north-south routes, farmers would need to find and domesticate new plants whenever the climate changed.
As a result, agriculture spread two to three times faster across Asia and Europe than it did up and down the Americas. Over the span of centuries, this small difference had a very big impact. Increased food production allowed for more rapid population growth. With more people, these cultures were able to build stronger armies and were better equipped to develop new technologies. The changes started out small—a crop that spread slightly farther, a population that grew slightly faster—but compounded into substantial differences over time.