Disease: Native Americans had no immunity to the diseases that Europeans brought with them, such as smallpox, measles, and influenza. These diseases spread rapidly through Native American populations, causing widespread death and devastation.
Warfare: Europeans often engaged in warfare with Native Americans, either to gain land or to suppress resistance to their authority. This led to the loss of many Native American lives.
Disruption of traditional lifestyles: The arrival of Europeans disrupted the traditional lifestyles of Native Americans, leading to social and economic dislocation. This contributed to their vulnerability to disease and warfare.
Displacement: Native Americans were often displaced from their traditional lands, which were taken over by European settlers. This led to food shortages and social and cultural disruption, adding to the mortality rate among Native Americans.