Bajuni are of mixed origin the majority of their dna is Garre but they have a lot of foreign blood too but o think they have been in the islands for long. Bravanese people on the other hand are most likely settlers who mixed with different populations.Only the Swahilis (Bravanese/Bajuni) are actually native to Somalia. The rest of the Bantu were brought in as slaves. Their population explosion isn't a surprise either, they are mainly farmers whereas Somalis are pastorialists and they have barely been affected by the civil war