They come from the same root. I don't understand this point.
Please link the paper. All the papers I've read indicated near total population replacement of indigenous African groups (pygmies, cushites, and khoi-san) by West African immigrants supported by genetics and cultural factors (artifacts, farming tools, language,etc.) in last 2-3 kya.
Lol, I never claimed the Bantu Expansion never happened. I just told you the fact that we don't have any clear cut evidence if Bantus ever lived in Cameroon, i.e. no DNA material from skeletal remains in Cameroon related to proto-Bantu speakers.
Everything the theory is based on is genetic variances between different groups and the other things you mentioned. But you're moving the goalpost because my original point never touched on the Bantu expansion.
What I mean by "immense timescale" is the complex peopling of West Africa, and how through time, every group would have exchanged some of their genetic material to a gradient degree from different basal sources, or it's an endemic shared signature, which the computational models fail to capture correctly. But this had nothing to do with the Bantu expansion.
You claimed the current West Africans and Bantus were the same people. This is probably lazy use of semantics on your end, but it's very ignorant. Bantus split from 'Niger-Congo A' over 5000 years ago. Let me remind you that that number is based on a somewhat erroneous linguistic reconstruction, and could even predate it.
Everyone knows that niger-congo speakers are related, but not related enough to be considered the "same people." They speak different languages, have different cultures, etc.
As I previously stated, even the Niger-Congo phylogeny is differentiated, but we can't go deep into this since West African archaeogenetics research is at its infancy, but there will be more focus on that region; they've developed new techniques and improved the technology to extract the genetic material, which was nearly impossible in the past from areas with high humidity that caused degradation.