The central thesis that Diamond argues in his convincing work is that the way that world history has played out is not as a result of any difference between ethnicities and races, as was assumed for so long. White Eurasians for example thought that the reason they dominated the world for long periods was thanks to their God-given status as superior beings over other ethnicities. Diamond successfully debunks this myth by arguing that difference between different groups of people was actually unimportant, and in fact had nothing to do with which group came out on top of the struggle for dominance in world history. Taking far-reaching examples to support his case, Diamond argues that environment is the single biggest and most important factor that determines whether a people group flourishes or not:
...Aboriginal Australian hunter-gatherers, variously transplanted to Flinders Island, Tasmania, or southeastern Australia, ended up extinct, or as hunter-gatherers with the modern world's simplest technology, or as canal builders intensively managing a productive fishery, depending on their environments.
The gap between those groups who became hunter-gatherers, and those who set up intensive farming, is one of the key differences between those groups who stay undeveloped and those who develop their infrastructure and thus achieve dominance over other groups. It is all down to environment, Diamond argues.
Interestingly, in 1493, Mann disagrees from Diamond in arguing that differences between ethnicities were actually important in the way that global history played out. The biggest example he comes up with is the natural resilience and greater immunity that black Africans had, which is why they came to be used as slaves in such big numbers because they were more effective than any other group working in areas where mosquitoes were rife. Mann also looks at the disease that not only Europeans brought with them to the Americas, but the way that this was a two-way exchange, and the massive impact this had upon Europe in introducing potato blight, for example.