Final answer:
Spanish explorers brought diseases such as smallpox to the Native American populations, leading to a catastrophic decline in their numbers due to a lack of immunity. An estimated 80 percent of the indigenous population perished, with some regions experiencing reductions as drastic as from over a million to just 500 individuals.
Step-by-step explanation:
The diseases that Spanish explorers brought to the Native Americans, like smallpox, influenza, measles, and typhus, had a devastating effect on the size of their tribes. Native Americans had no immunity to these European diseases, and as a result, their populations experienced a massive decline. It is estimated that around 80 percent of the indigenous population of South, Central, and North America died as a result of these diseases, representing an epidemic with few historical comparisons. For example, on the Caribbean island of Hispaniola, the population decreased from over a million to just 500 in just over 50 years after European contact.