The diseases killed many Native Americans. That is a major force that shaped human encounters.
Student or Learner
It was disease, however, that ultimately destroyed the cultural integrity of many North American tribes - small social groups of related families. European adventurers exposed the Indians to bacteria and viruses against which they possessed no natural immunity...However horrific the crisis may have been, it demonstrated powerfully just how much the environment - a source of opportunity as well as devastation - shaped human encounters throughout the New World..
What does this "shaped human encounters" mean? Did the environment determine how to meet other people? Due to disease, the Indians were reluctant to meet white people?
the way of meeting people? Does it mean "if you meet people, you can die"?
What human encounters did it mean?
Avoiding whites with potential disease?
It changed their experiences. It made history be different than it would have been without the diseases. Had the Natives spread disease to the white man that led to decimation of the white population, then Europeans may not have come to America in great numbers. Native would have continued in their isolation. History would be different.
Or, if there were no disease to harm either side, the battles for land and control might have been different.