A paucity of written historical evidence forces the student of early Somalia to depend on the findings of archeology, anthropology, historical linguistics, and related disciplines.

Such evidence has provided insights that in some cases have refuted conventional explanations of the origins and evolution of the Somali people. For example, where historians once believed that the Somalis originated on the Red Sea's western coast, or perhaps in southern Arabia, it now seems clear that the ancestral homeland of the Somalis, together with affiliated Cushite peoples, was in the highlands of southern Ethiopia, specifically in the lake regions. Similarly, the once-common notion that the migration and settlement of early Mus,lims followers of the Prophet Muhammad on the Somali coast in the early centuries of Islam had a significant impact on the Somalis no longer enjoys much academic support. Scholars now recognize that the Arab factor--except for the Somalis' conversion to Islam--is marginal to understanding the Somali past. Furthermore, conventional wisdom once held that Somali migrations followed a north-to-south route; the reverse of this now appears to be nearer the truth.

Increasingly, evidence places the Somalis within a wide family of peoples called Eastern Cushites by modern linguists and described earlier in some instances as Hamites. From a broader cultural-linguistic perspective, the Cushite family belongs to a vast stock of languages and peoples considered Afro-Asiatic. Afro-Asiatic languages in turn include Cushitic (principally Somali, Oromo, and Afar), the Hausa language of Nigeria, and the Semitic languages of Arabic, Hebrew, and Amharic. Medieval Arabs referred to the Eastern Cushites as the Berberi.

In addition to the Somalis, the Cushites include the largely nomadic Afar (Danakil), who straddle the Great Rift Valley between Ethiopia and Djibouti; the Oromo, who have played such a large role in Ethiopian history and in the 1990s constituted roughly one-half of the Ethiopian population and were also numerous in northern Kenya; the Reendille (Rendilli) of Kenya; and the Aweera (Boni) along the Lamu coast in Kenya. The Somalis belong to a subbranch of the Cushites, the Omo-Tana group, whose languages are almost mutually intelligible. The original home of the Omo-Tana group appears to have been on the Omo and Tana rivers, in an area extending from Lake Turkana in present-day northern Kenya to the Indian Ocean coast.

The Somalis form a subgroup of the Omo-Tana called Sam. Having split from the main stream of Cushite peoples about the first half of the first millennium B.C., the proto-Sam appear to have spread to the grazing plains of northern Kenya, where protoSam communities seem to have followed the Tana River and to have reached the Indian Ocean coast well before the first century A.D. On the coast, the proto-Sam splintered further; one group (the Boni) remained on the Lamu Archipelago, and the other moved northward to populate southern Somalia. There the group's members eventually developed a mixed economy based on farming and animal husbandry, a mode of life still common in southern Somalia. Members of the proto-Sam who came to occupy the Somali Peninsula were known as the so-called Samaale, or Somaal, a clear reference to the mythical father figure of the main Somali clan-families, whose name gave rise to the term Somali.

The Samaale again moved farther north in search of water and pasturelands. They swept into the vast Ogaden (Ogaadeen) plains, reaching the southern shore of the Red Sea by the first century A.D. German scholar Bernd Heine, who wrote in the 1970s on early Somali history, observed that the Samaale had occupied the entire Horn of Africa by approximately 100 A.D.