The core idea of the geography hypothesis is that the physical, ecological, and geographical environment is the primary factor in a country’s economic development. This theory suggests that nature, in a sense, deals a country its hand, and that hand largely determines its economic future. There are three main versions of this argument:

1. The Climate Story This is the oldest version of the hypothesis, dating back to thinkers like Montesquieu. The argument is simple: hot climates make people less inclined to work hard and therefore less productive. Temperate climates, in contrast, foster a stronger work ethic and greater prosperity.
2. The Productivity Story A more modern version, championed by economist Jeffrey Sachs, argues that geography directly impacts technology and agricultural productivity. The claim is that temperate zones are fundamentally more productive than tropical zones, especially in agriculture. This initial advantage in food production allowed temperate regions to support denser populations and develop more advanced technologies, giving them a permanent leg up.
3. The Disease Story This version focuses on the role of disease in trapping countries in poverty. Tropical regions, for example, carry a heavy burden of diseases like malaria. A high disease burden can cripple a workforce, reduce life expectancy, and drain a country’s resources, making it nearly impossible to achieve sustained economic growth.

The geography hypothesis is intuitive, but it struggles to explain major shifts in global wealth. Why are some places that were historically rich now relatively poor, and vice-versa? To explore that, we need to turn from the physical environment to the mental one: the world of culture.