Jared Diamond is a professor in UCLA specializing in biology. He endeavors to explain why world history unfolded as it did. Why did certain groups dominate while others ended up so far behind? He starts with a journey to Papa New Guinea. His theory is generally that everybody is the same but certain locations allow for better opportunities. Eurasia had the better crops and animals for domestication. Domestication also allow for germs to develop. Also the east west travel within common climate allowed an easier trade route which advanced technologies even further. And geography explains why China and other monolithic middle east empires stagnated whereas Europe's geography favors a bulkanized map and tougher competitions from close neighbors.
In general terms, I have no big problems with his theory. It doesn't add a whole lot to understanding the world. He's not discover something new as much as reorganizing what everybody already knows. There are ideas and concepts that are ignored too easily. There is a lot of generalization but that's the theory. It's trying to generalize the whole of human history with a few simple ideas. The theory is noteworthy for what's not in it as much as what's in it. It's just that I wish there is some definitive mathematical evidence to verify his theory. Also world history has a tendency to be more muddy than what's presented here.
