In his book, Guns, Germs, and Steel: The Fates of Human Societies, Jared Diamond's purpose is to explain why history unfolded the way it did and why some countries progressed more than others. Diamond's explanation to why some nations are flourishing today while others remain to be third-world countries is unlike any other reasoning presented in the past because he relies on evidence and events from actual fields of study rather than giving credit to an individual race being born with more 'units' of intelligence. Diamond purposes that due to plants and animals that are easy to tame, societies and civilizations in Eurasia were able to move from being hunter-gatherers to farmers and agriculturists; he mentions how advancements in agriculture introduced the division of labor which in result led to the development of weapons. Due to the idea of concepts and goods being easily spread on an east-west axis rather than a north-south axis and the Americas having many geographical constraints, Eurasia had more doors of progress open to itself. Lastly, Eurasia's population was more immune to diseases because it consisted of many different types of people from different backgrounds.