By about 7000 B.C. at the latest, linguistic evidence indicates that both Cushitic speakers and Omotic speakers were present in Ethiopia. Linguistic diversification within each group thereafter gave rise to a large number of new languages. In the case of Cushitic, these include Agew in the central and northern highlands and, in regions to the east and southeast, Saho, Afar, Somali, Sidamo, and Oromo, all spoken by peoples who would play major roles in the subsequent history of the region. Omotic also spawned a large number of languages, Welamo (often called Wolayta) and Gemu-Gofa being among the most widely spoken of them, but Omotic speakers would remain outside the main zone of ethnic interaction in Ethiopia until the late nineteenth century.

Both Cushitic- and Omotic-speaking peoples collected wild grasses and other plants for thousands of years before they eventually domesticated those they most preferred. According to linguistic and limited archaeological analyses, plough agriculture based on grain cultivation was established in the drier, grassier parts of the northern highlands by at least several millennia before the Christian era. Indigenous grasses such as teff and eleusine were the initial domesticates; considerably later, barley and wheat were introduced from Southwest Asia. The corresponding domesticate in the better watered and heavily forested southern highlands was ensete, a root crop known locally as false banana. All of these early peoples also kept domesticated animals, including cattle, sheep, goats, and donkeys. Thus, from the late prehistoric period, agricultural patterns of livelihood were established that were to be characteristic of the region through modern times. It was the descendants of these peoples and cultures of the Ethiopian region who at various times and places interacted with successive waves of migrants from across the Red Sea. This interaction began well before the modern era and has continued through contemporary times.

During the first millennium B.C. and possibly even earlier, various Semitic-speaking groups from Southwest Arabia began to cross the Red Sea and settle along the coast and in the nearby highlands. These migrants brought with them their Semitic speech (Sabaean and perhaps others) and script (Old Epigraphic South Arabic) and monumental stone architecture. A fusion of the newcomers with the indigenous inhabitants produced a culture known as pre-Aksumite. The factors that motivated this settlement in the area are not known, but to judge from subsequent history, commercial activity must have figured strongly. The port city of Adulis, near modern-day Mitsiwa, was a major regional entrepôt and probably the main gateway to the interior for new arrivals from Southwest Arabia. Archaeological evidence indicates that by the beginning of the Christian era this pre-Aksumite culture had developed western and eastern regional variants. The former, which included the region of Aksum, was probably the polity or series of polities that became the Aksumite state.