Why were your primitive ancestors practically free of the pestilences that ambushed their civilized successor and have plagued us ever since?

Answer 1

Pestilence is a disease that kills multiple persons at close to the same period of time. It is not a new disease but one that has multiple opportunities to spread. When man lived alone or in small groups they would get the disease and die thus ending the spread. Enter civilization. We are all crowded together in cities, poorer sanitation and vermin that carry disease (fleas and rats) live on the refuse and waste of humans. When all this is all in one place you have ideal conditions for the spread of disease. In the past the disease was limited to one or at most a few individuals and therefore not much of a threat (unless you are one of those poor individuals). But now one person can infect multiple people and those can, in turn, infect others leading to the death of hundreds and thousands. Also, in the past, people tended to be wary of strangers and had very little contact with others. They tended to stay in certain regions where the food was readily available. As civilization evolved so did the need for travel, to get supplies and to conduct business. Thus one infected individual can not only infect the town or city he lives in but, in his travels, can infect other towns and cities, sometimes world-wide.