The epilogue of this book is meant mostly to suggest directions for further research. Diamond wants to indicate what sorts of questions historians should pursue.
Importantly, Diamond also has something to say about how historians should try to do their work. He thinks that history should become more like a science. Historians should, he says, use natural experiments (like the one about the Polynesians that he describes in Chapter 2) to uncover truths about human history. He believes that historians should start to do this so that they will be able to make more definitive statements about history.
So, the overall purpose of this epilogue is to suggest that historians should use these natural experiments to make history more like a science.
The epilogue of Guns, Germs, and Steel by Jared Diamond is entitled “The Future of Human History as a Science.” This title gives you a clue as to Diamond’s thinking at the end of the book, his interpretation of what the future of human history should entail. His thought is that history should be examined more scientifically. The epilogue explains that there are shortcomings to his thinking in that it is nearly impossible to create experiments in society and geography that can be replicated because there are too many variables including human nature, environment, and the length of time that would be necessary to carry out such experiments.
Jared Diamond espouses the idea of geological determinism which theorizes that Europeans became dominant because they had better raw materials and more favorable environmental conditions that those in the Fertile Crescent and China. There were also power struggles, especially in China. Whereas the Europeans were open to world exploration, the Chinese were facing civil unrest as they battled the Eunuchs. Diamond suggests that the power struggles be looked at only after the geographical situations are examined, thus making human history into a science.