Having examined the effects of geography on food production and some aspects of cultural development in Parts I and II, Diamond turns to consider the reasons that some societies developed certain technologies ("Guns" and "Steel") and deadly pathogens ("Germs") in Part III. As he puts it, he attempts to show "how the ultimate cause of food production led to the proximate cause of germs, literacy, technology, and centralized government." First he argues that the presence of livestock in Eurasian and African societies facilitated the spread of pathogens that would prove deadly for Native Americans. Then he demonstrates how different writing systems, again in Eurasia, emerged from a handful of written languages. Finally, he concludes Part III by examining how societies developed technologies unequally, and how societies developed from egalitarian hunter-gathering to highly stratified polities capable of extracting wealth and labor from their subjects.