Cultures are not spontaneous growths, nor do they evolve randomly. They adapt to their environments—and many thinkers have urged attention to those environmental conditions as the most important shapers of culture and behavior.
The specific thinker cited by Mitt Romney, Jared Diamond, has laid stress on the advantages the cultures of Eurasia obtained from the availability of domesticable animals (absent from the Americas) and from a geography that spread immunities to disease across the vast east-west band from Iberia to China.
Kenneth Pomeranz has argued that economic leadership passed from China's Yangzi Delta to England in the 18th century because China bumped into resource constraints that England could escape thanks to abundant coal and the colonization of North American agricultural lands.
Charles Mann has argued that the arrival of malaria from Europe after 1493 reshaped the economies of the Americas. Before malaria, the warmest parts of the western hemisphere had been the most developed; by the 19th century, the advantage had passed to cooler zones: Argentina, Uruguay and southern Brazil in South America; the United States in the north.
Jared Diamond restates this viewing in today's New York Times:
One such geographic factor is latitude, which has big effects on wealth and power today: tropical countries tend to be poorer than temperate-zone countries. Reasons include the debilitating effects of tropical diseases on life span and work, and the average lower productivity of agriculture and soils in the tropics than in the temperate zones.
A second factor is access to the sea. Countries without a seacoast or big navigable rivers tend to be poor, because transport costs overland or by air are much higher than transport costs by sea.
A third geographic factor is the history of agriculture. If an extraterrestrial had toured earth in the year 2000 B.C., the visitor would have noticed that centralized government, writing and metal tools were already widespread in Eurasia but hadn’t yet appeared in the New World, sub-Saharan Africa or Australia. That long head start would have let the visitor predict correctly that today, most of the world’s richest and most powerful countries would be Eurasian countries (and their overseas settlements in North America, Australia and New Zealand).
Disease can be overcome, as malaria has been in the developed world—Italy in the 1940s, the US in the 1920s.
Global trade can overcome the unequal access to resources studied by Kenneth Pomeranz.
Otherwise, however, this geographic cluster of answers is, if anything, even more fatalistic than the cultural explanations. The culture of sub-Saharan African can change, but Zimbabwe will not move closer to the ocean.
Yet the geographic explanation attracts many people of goodwill, because—if it does not offer much hope that global disparities will ever be overcome—it does offer the next best thing: an account of global disparities that exonerates the laggard from any responsibility for their laggardness.
The geographic explanation for divergent development is highly in fashion these days, but it's also deeply troublesome.
For example: Australia was one of the poorest, most under-developed places on Earth 200 years ago. Today Australia ranks among the very richest. Yet Australia has not moved in the interim.
Jared Diamond's explanation for this might be that the new inhabitants of Australia brought with them the advantages developed under more favorable geographic conditions: the guns, germs, and steel of his title. Okay. But those advantages are now present in Australia, available to be emulated and adopted. Yet the wealth gap between the descendants of the European immigrants and the descendants of the aboriginal inhabitants remains very large.
Group differences in economic development persist long after the geographic basis for them has receded.
Nor is it obvious in advance of the fact what constitutes a geographic advantage. In his New York Times op-ed Wednesday, Diamond stressed the importance of access to the sea. Yet that's true only until it ceases to be true. The coastal cities of China led the world economically in the middle ages. They seem poised to lead the world again in the 21st century. Yet there were 500 years in between when China fell desperately behind the rest of the world, almost vanishing as an industrial and trading power by 1950. There was no less access to the sea in 1950 than in 1400, no more access in 2010 than in 1950. Something else changed over those years.