Karl Marx understood history as driven by class structure and class conflict, with socioeconomic factors driving historical realities. In any historical society, regardless of whatever geographic or historical context might enter into play, these patterns of social stratification and of conflict between the various subsections of that structure would be continually present across time. Of course, this is not to say that these structures are entirely static or unchanging: socioeconomic structures can be overthrown, with new structures and economic realities arising to replace them. However, the theme of class struggle is one that, for Marx, has endured throughout history, and across the various socioeconomic upheavals and transformations that have unfolded over time.
Marx proceeds to suggest that the Age of Exploration contributed greatly in shaping one of these critical moments of socioeconomic upheaval, arguing that the discovery of the Americas (and also of new routes to India) shaped the dissolution of the older feudal economy. As he writes:
The discovery of America, the rounding of the Cape, opened up fresh ground for the rising bourgeoisie. The East-Indian and Chinese markets, the colonisation of America, trade with the colonies, the increase in the means of exchange and in commodities generally, gave to commerce, to navigation, to industry, an impulse never before known, and thereby, to the revolutionary element in the tottering feudal society, a rapid development.
In this fashion, the Age of Exploration is understood as representing a breakthrough, one which would set the stage for the later Industrial Revolution to take shape and eventually the Industrial Age. The discovery of the Americas thus serves as a precursor to these dramatic transformations and represents a critical moment within the larger course of history as Marx perceives it.