The central argument of Diamond's classic work on world history and social anthropology is based around his central argument that attempts to respond to "Yali's Question," an acquaintance of his who asked Diamond one day why it is that the whites in the world had done so well and achieved a position of supremacy over other ethnicities in the world. Diamond's answer to this question is fascinating in so many ways, but it principally states through his research and hypothesis that supremacy in the history of man is not due to differences of ethnicity but due solely to the environment itself:
I would say to Yali: the striking differences between the long-term histories of peoples of the different continents have been due not to innate differences in the peoples themselves but to differences in their environments.
Diamond therefore argues in effect that ethnic and racial differences had no impact on the way that world history played out. What was much more important was the number of different crops civilisations had access to and also how many domesticated animals they had within their region. These were key components in determining the speed in which nations advanced or not.
Mann in 1493 builds on this work by examining how the voyage of Columbus transformed the world more than any other single event in the history of man. He looks at the way in which through this voyage white Eurasians were able to gain dominance over South America, and through that how globalisation entered the world through the export of South American silver, crops and also slaves. Mann focuses particularly on disease and also environment, using some of Diamond's central arguments and developing them in different ways and approaches.