Sounds like Bantu myths and "we wuz Somali".
No offence to you but unless we find a 1000 year old Bantu skull, this is not true.
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Not all bantus are the same The whole somali bantu term to describe them was developed recently. So called bantus in Somalia are divided mainly in two groups.
1)indigenous: shiidle, reer shabelle and eyle are believed to be indigenous in the sense that they lived in Somalia for a really long time. They are a mixture of bantu+hunter gatherer. Most of them have nothing to do with the slave trade, they lost their original language and speak somali. Some of them look more cushitic or borderline cushitic. It's likely that the area south of Mogadishu/Merca was inhabited by them before the 11-12th century
2) slave descendants: These are also known as Gosha or mushunguli. They are descendants of slaves brought in somalia in the 19th century from Tanzania/malawi. Some of them still speak mushunguli, they live in the shabelle-juba regions.
These two groups have merged recently and are collectively called Madowweyne but they have very different origins.
To be honest we don't even have a 1000 somali skull that was analyzed so I don't get your point. If we really on oral somali history the hiraan bantus are mainly indigenous and were probably there before ethnic somalis came over and conquered the area