This is a graphical representation of the genetic ancestral proportions in Ethiopian tribes, with relevance to Somali tribes by way of neighborly relation. For simple reference, the red* haplogroup (J) and purple* haplogroups (K) are purported Native Near Eastern/Arab haplogroups. Meanwhile the green, blue and orange are purported native African haplogroups:
As you can see, the only Ethiopian tribe with all native black components are the Nilo-Saharan. The rest of the Ethiopian tribes--including the Cushitic, Omotic and Semitic, a variety of which are found in Somalia--are proportionally mixed race, notably with the J and K Near Eastern haplogroups.
Reconciling this discovery, the prevailing assertion is that the most pure and ancient Ethiopians, the Nilo-Saharan tribe, are the original inhabitants of Ethiopians. The rest are infected pretenders or else invaders. For black purposes it doesn't matter which, both are thieves on black people's land. To relate this all back to Somalis, the same trend is likely true of Somalia and its mixed and pure bred tribes.