> The "vast distances" were just some places humans could establish cities. The "vast distances" were the whole planet and an ever increasing population, even

> The "vast distances" were just some places humans could establish cities. The "vast distances" were the whole planet and an ever increasing population, even before the explosion in numbers later. See the reports about the impact the Mongols or the plague, both killing large parts of the populations back then, with great impact on the environment. Humans always had a large impact on their environment especially after inventing agriculture.