Ooops, I misread that last sentence.
Its actually absolutely doable because its along the Okavango river. Around 1k years ago a Cushtic/proto-Bantu population moved down from East Africa into Khoi lands. In doing so both animals like cattle, sheep and goats and pottery were introduced.
There is a palm Phoenix Reclinata the Senegalese date Palm that grows along the river, it can just become the staple that along with fish and dairy can make a wholesome diet all of which can be dried for storage or trade.
There is record of cows being riding animals that were trained to fight among Khoisan according to the Dutch so the breeding of a specialized cow for travel seems more than doable and their trade of animals and even metal crafts for say idk gold or the use of metal weapons against less east african influenced Khoi and San could make a stable mine working population.
You can always find a way to push East African technological transmission further back and make it a totally Bos taurus africanus herding population moving down by idk maybe a few thousand years since they've been domesticated like 9-7K years ago around the Sudan Egypt border.
Maybe the end of the Neolithic Subpluvial caused a spiritual call to a marginalized group of Tenerians with a leader having the desire to find a second great river like the Nile and a small band of extremists over the generations inter marrying with Nachikufan baTwa and other pre-Bantu peoples along the way eventually find a sedentary date cultivating fisher Khoisan folk living in villages along the Okavango to intermarry with?