is anyone good at paraphrasing? pls help!!

Bantu speakers first divided in two groups: Wide and Narrow Bantu. The modern languages of the first are spoken only on and around the Cameroon grasslands, while all the other Bantu languages belong to the second. Therefore, in practice “Bantu” usually refers to Narrow Bantu. Narrow proto-Bantu emerged from Wide Bantu in the Sanaga valley just south of the grasslands of western Cameroon. Until recent times, this huge expansion was believed to have been brought about by a single vast human migration.

It proved however to be exceedingly difficult to establish the genetic subdivisions of Narrow Bantu that such a migration would have produced, mainly because the daughter languages have borrowed so much from each other and otherwise changed over the past millennia that much of the evidence for their exact genetic relationships has been erased.​