Guns, Germs, and Steel by Jared Diamond attempts to answer Yali's question about why Europeans have so much "cargo" (material wealth and technology) and Papua New Guineans so little. Diamond notes that people from many different regions and cultures are equally intelligent and work equally hard, making this disparity puzzling.
In his book, Diamond argues that there are geographic and environmental factors that led to to variation in wealth and technological development. Among the main factors were those that affected the agricultural transition. Regions with domesticable plants and animals and appropriate rainfall and soils can generate surplus food by farming, leading to specialization of labor, which is an essential precondition for development of advanced technology. This meant that when Europeans encountered other cultures, their more advanced military technology led to conquest. He also argues that the resistance to epidemic diseases resulting from early urbanization also was a major factor in colonialism, as European diseases decimated many indigenous populations.