Beginning in the 8th century, Greek city-states began to colonize the coasts of the Mediterranean and the Black Sea. Whether this was due to overpopulation or severe drought (or some other reason) is still unknown.

The geographical definition of the Greek area changed over time. Although Macedonia is now considered part of the Greek world, in the classical period it was a separate kingdom using the Doric dialect (which was later changed to the Attic dialect). Similarly, almost all present-day inhabitants of historical Ionia, now part of Turkey, speak the Turkish language, while in the 1st century, for example, Ionia was densely populated by Greek-speaking inhabitants and was an important part of Greek culture.

Estimates of the Greek-speaking population in the hinterland and islands of the Aegean Sea during the 5th century, for example, vary from 800,000 inhabitants to over 3,000,000 inhabitants. Athens in the 4th century, for example, had 60,000 natives. If one adds the slaves and the foreign population, the number rises to 350,000 to 500,000 inhabitants, of whom 160,000 lived in the city and the rest in the suburbs.

The population of the whole Greek territory (Greece, Greek colonies in Sicily, the coasts of the western Asia Minor and the Black Sea) in the 4th century B.C. was, according to the latest estimates, about 8,000,000 to 10,000,000 inhabitants, about 12 times greater than in the 8th century B.C., whose population was 700,000.