According to the Epilogue of Guns, Germs, and Steel:
How does Diamond explain the fact that it was Europe and not Southwest Asia, where agriculture and civilization originated, that ended up spreading its culture to the rest of the world? And how did China lose its lead?
On eNotes, we ask that you post one question at a time. In the future, please do so. In this case, I will answer both of your questions, but perhaps more briefly than I would be able to answer a single question.
The answer to the first question is found on pp. 410 and 411 of Guns, Germs, and Steel. Diamond’s discussion of this issue is very short and I recommend that you have a look at it yourself. Basically, Diamond says that the Fertile Crescent in Southwest Asia lost its lead because its environment became degraded. He says that the environment was originally good for farming at a low level but it could not sustain high intensity farming. As people cut down the trees and used other resources necessary for a dense population, he says on p. 411, they “committed ecological suicide by destroying their own resource base.”
For China, Diamond has to speculate more and his speculation about China is much longer than his discussion of the Fertile Crescent. He says that China lost its lead because of its geography. China is not divided up into a lot of little areas that are split by mountains, rivers, and other geographical features. This meant that all of China could be ruled by one government that did not have any serious rivals. Because China had no competition, it did not have to progress. By contrast, Europe was split up into peninsulas (Italy, Iberia), and islands (Britain, Ireland), and was divided by mountain ranges and rivers. This meant that Europe developed lots of relatively small countries. They had to compete with one another so they took every opportunity to advance themselves through technology. China lost its lead, he says, because its geography allowed it to be complacent while Europe’s geography made its countries compete really hard with one another.