Where you see certainty I see ambiguity. None of what you are reading in those links confirms your forceful statement of facts where no such facts exist.
Nothing about any of the posted information is ambiguous. On the other hand, you decided to extract partial quotes that fit your narrative in a way to be purposefully deceptive.
Researchers saying "we are not completely certain but the evidence appears to indicate X" is not logically equivalent to "we have no idea why X happens"
