Like I say, I agree with you in the broader sense but I was making a finer point here. i.e. not whether the premise is true, but just what the scope (or even how valid) was of the research that demonstrated the premise.
GP provides sources in a sibling thread where the discussion is further elaborated.
I don't think there is scientific a consensus on this yet. I strongly doubt that there is reasonable study that would make the split 50%, 50%, 0%. It is too round, too nice to be true.