Language related to Yoruba, but culture to Baatonu (Bariba)
there are two Dassas, according to wiki.
Do you mean the one in Burkina Faso or the other one in Benin Republic.
true, the British/French presence created some new borders. The divisions were based on slave trade routes, to some extent.
Likewise in the north, many peoples were forced to relocate and move south due to inter-tribal and religious warfare.
There are very isolate but are culturally more similar to Bariba, they are closer to the eastern part of Niger state, I am really facinated about this and i think more research should be done into ede language clusters in Benin republic, Dassa is a town similar to abeokuta in its foundation, still very little is known about them, Colonization has really blinded a lot of people, The artificial lines created by the british/french has hindered cultural knowledge,
its quite possible they could be Yoruba, though I doubt it. But I dont know much about them anyway. They may be related to Yoruba in some way, much like the Fon and Ewe. I could still be wrong however.
However, that region they're native to, borders northern kwara and Niger states in Nigeria.And the Nupe tribe (I think). Maybe people from there have heard of them. And are you sure they arent Nupe?
Well The Mokole in Northern Benin are normally found in and around the town of Kandi,
There language is closely related to Yoruba I mean close, Very little is known about them some suggest they are reminants of oyo ile that left with the Alafin into exile in Bariba land during the first collapse of Oyo by the Nupe,