Actually false, it's a common misconception that Somalis are a mixed breed between bantu people/arabs. But the reality is that Somalis have been a indigenous people for thousands of years, and are probably as pure as they come. The "caucasoid" features are completely somali and not the result of "mixture".
Anyway, the 'incel'-tier features Somalis have likely come from inbreeding (bulbuous headshape, high foreheads), that in combination with a skinny build (from a nomadic lifestyle), we truly fucked ourselves.