Question

Why did the Native American Indian population change so much ?

Answer 1

Ailments brought fourth by the mass immigration of those seeking a new life. I’m addition to this fact, many were killed off by those seeking more land.

Answer 2

Tragically, when the Europeans came to the Americas, they brought diseases that the natives were not yet exposed to. Therefore, many Native Americans died from these diseases. Those who survived the diseases were often mistreated by the Europeans. Some were made slaves, others fled west, etc.