Jared Diamond argues that the three major factors that separate the haves from the have-nots in world history are the development of agriculture, the accident of geography, and resistance to infectious diseases.
Diamond attributes these three factors to the rise and dominance of European culture, particularly in the last five hundred years. He says this rise has nothing to do with innate superiority or intelligence on the part of Europeans, but on developments that in hindsight seem largely accidental.
The Europeans adopted agriculture early, due to the accident or good luck of the presence of many wild wheat crops suitable to cultivation in the Fertile Crescent, which spread northward. The Europeans also had the good luck to find an easy supply of animals suitable for domestication. With abundant and relatively secure food supplies from these two sources, European (including Middle Eastern) society was able to diversify and develop technological expertise and complex writing systems that would later give it advantages over other groups, such as Native Americans and Indigenous Australians.
A geography that lacked natural barriers also assisted European development, as groups living in that part of the world were able to benefit from cross-cultural exchange. They had more opportunity to borrow and build on the achievements of other cultures than more isolated areas of the world.
Finally, the Europeans had a significant advantage early on in developing an immunity to many illnesses that wiped out native populations. Diamond attributes this, in part, to their living in close quarters with domesticated animals. Europeans contracted diseases from these animals and subsequently developed immunities to them.