Final answer:
The primary cause of the dramatic decline in the Native American population after European contact was the introduction of contagious diseases such as smallpox, influenza, and measles.
Step-by-step explanation:
The main cause of the decline in the Indian population after the arrival of Europeans was the introduction of contagious diseases such as smallpox, influenza, and measles. Europeans had developed a resistance to these diseases over centuries of exposure, but the Native American population had no prior contact with them, leaving them incredibly vulnerable. In addition to diseases, other factors such as European enslavement, forced labor, and environmental depletion due to colonial infrastructure contributed to the decline in population. Acts of violence and displacement, such as the Trail of Tears, further exacerbated the Native American suffering.
One of the most devastating outbreaks occurred along the New England coast between 1616 and 1618, where epidemics claimed 75 percent of the native people. The forced changes in lifestyle and habitat due to European colonization also weakened Indigenous communities, leaving them susceptible to disease and malnutrition. Moreover, intentional or not, these diseases acted as agents of genocide, drastically reducing the Native American population, with estimates suggesting a drop from around twelve million in 1500 to just over two hundred thousand by the year 1900.