Final answer:
The primary reason that Greeks established colonies overseas in the Archaic period was economic expansion.
Step-by-step explanation:
The primary reason that Greeks established colonies overseas in the Archaic period was economic expansion. As the population expanded during this period, there was a shortage of farmland in Greece. Greeks sought new lands to farm and establish trade routes, leading them to establish colonies along the shores of the Black Sea, the northern Aegean, North Africa, and southern Gaul. These colonies became independent polis with their own laws and allowed the Greeks to cultivate other crops and engage in trade.