Why were people able to begin trading with others in the area?

When people first settled down into larger towns in Mesopotamia and Egypt, self-sufficiency the idea that you had to produce absolutely everything that you wanted or needed started to fade. A farmer could now trade grain for meat, or milk for a pot, at the local market, which was seldom too far away.

Cities started to work the same way, realizing that they could acquire goods they didn't have at hand from other cities far away, where the climate and natural resources produced different things. This longer-distance trade was slow and often dangerous, but was lucrative for the middlemen willing to make the journey.

The first long-distance trade occurred between Mesopotamia and the Indus Valley in Pakistan around 3000 BC, historians believe. Long-distance trade in these early times was limited almost exclusively to luxury goods like spices, textiles and precious metals. Cities that were rich in these commodities became financially rich, too, satiating the appetites of other surrounding regions for jewelry, fancy robes and imported delicacies.

It wasn't long after that trade networks crisscrossed the entire Eurasian continent, inextricably linking cultures for the first time in history.

By the second millennium BC, former backwater island Cyprus had become a major Mediterranean player by ferrying its vast copper resources to the Near East and Egypt, regions wealthy due to their own natural resources such as papyrus and wool. Phoenicia, famous for its seafaring expertise, hawked its valuable cedar wood and linens dyes all over the Mediterranean. China prospered by trading jade, spices and later, silk. Britain shared its abundance of tin.