How might one best describe the main ideas presented in Jared Diamond's non-fiction book, Guns, Germs and Steel?

UCLA professor Jared Diamond's bestselling non-fiction
work from 1997 began as a quest to find the answer to a simple question posed by a
friend of his:  How and why is it that throughout human history, European societies have
consistently dominated other cultures?  Diamond's task is an unwieldy one at best, and
although the book was a well-received best-seller, it was also not without its critics. 
Basically, Diamond's research led him to believe that Europeans had access to  favorable
geography which made it easier for them to develop stable agricultural societies; as
these societies inevitably evolved and changed, governments formed, and people began
organizing themselves into social structures and groups.  Stable agricultural societies
eventually develop ways to defend themselves, with the requisite weapons (guns), and
Diamond also argued that agricultural societies tended to expose each other to more and
stronger viruses and bacteria (germs), which became stronger immunities throughout the
generations, immunities that became most helpful during the years of European
colonization around the world.