In Guns, Germs, and Steel...what is Jared Diamonds main agrument?

One of the main themes and arguments in the book is the juxtaposition of theories of race and biology with those of geography and biogeography. Perhaps the most used explanation in trying to explain the different timing of developments on different continents or the conquests of certain groups over others has been a racial or biological one that assumes a racially superior or more intelligent society. Thus, under these theories, the most intelligent, racially superior groups first make inventions, develop new innovations, and conquer other groups. It is "survival of the fittest, or best." This explanation has been used to justify wars, colonization, and slavery.