Since Diamond is a scientist by training, it is not surprising that he uses science to construct history at many points in this book. Some examples of how he does this include:
- His discussion of natural selection and the natural history of various plants in Chapter 7. There, he uses science to determine what kinds of plants would have been feasible and/or attractive for people to domesticate.
- His discussion of how diseases evolve in Chapter 11. There, he uses science to explain how and why some diseases evolve to become epidemic diseases that persist in a population. The presence of these diseases in the "Old World" and their absence in the "New World" are very important to Diamond's history.
- His discussion in Chapter 5 of radiocarbon dating. Here, he uses science to help determine when the domestication of plants began in various places.
In these ways and others, Diamond uses science to help construct a history of how some areas came to have "guns, germs and steel" while others did not.