As an environmental historian, Marks’s emphasis throughout The Origins of the Modern World is on the environment and how human societies have interacted with it. For example, certain popular spices were once available only from Indonesia, which affected the trade and economic significance of Southeast Asia and its importance in relation to trade networks. Another example is how the climactic phenomenon the Little Ice Age may have helped cause social and political unrest throughout Eurasia in the late medieval and early modern eras.

In fact, Marks identifies the major turning points in human history as times when humans’ relationship with the environment changed: the “agricultural revolution,” when humans first started farming and establishing permanent settlements, and the “great departure,” when industrialization and scientific agriculture let human civilization transcend natural limits on how many crops could be gotten out of soil. Nevertheless, Marks does not view the environment and climate as the only drivers in history, holding that the presence of large amounts of coal in Britain alone did not ensure that the Industrial Revolution would have begun in Britain. Instead, it was a result of a series of complex circumstances, such as Britain’s position of international power after the Seven Years’ War, the British government’s policies of mercantilist control over trade, and the fact that Britain through its extensive trade could supply itself with food and necessary raw plant materials without needing to use much land in Britain itself.