In what ways does Diamond use science to help construct history in Guns, Germs, and Steel?

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.