Paternally: North African. Looking at long distances: Horn of Africa.
Maternally: East African and North African.
North African cause of migration: the desertification of the Sahara Desert (look up the African Humid Period).
The African population that make up the genetic coding of Somalis: Nilo-Saharans.
Essentially Cushitic people (not Ethio-Semitic people), are essentially an ancient mix of Afro-Asiatic North Africans and Nilotic indigenous Africans.
How did these Afro-Asiatics look like? We don't know.
What we do know is that Somalis genomically have 40% Eurasian (North African and West Asian) autosomal dna (every chromosome but the sex chromosome (i.e. Y-DNA in males)) and 60% African autosomal dna.
Considerations that prove it:
Pastoralism probably came from this paternal group. However, Somalis domesticated the Camel and other animals that are indigenous to the landscape.
Certain genes, such as SLC24A5, which encodes skin tone, are found among Somalis at about 60%. On a genetic level, this is has an allele that can either be expressed or not expressed. If you have allele AA or AG, you can express it. GG and you cannot (i.e. dark skin tones). I suspect my family has a mix of A and G, due to the diverse range of skin tones we all have, which is cool.
Ancient DNA suggests that Somalis (and other East Africans involved in the Savanna Pastoral Neolithic) are related to a degree with the Natufian Pre-Pottery Culture.
Our paternal haplogroup structure is common among Afro-Asiatic speakers, which is probably why we speak an Afro-Asiatic language as opposed to a Nilo-Saharan one.
The migration patterns of our people from the ancient past line up with the events of the desertification of the Sahara desert (which was a savanna, and thus perfect for pastoralism as a food production strategy).
This is my guess. Could be wrong, I'm not an expert. Just someone who read some shit.