i totally agree that the ubiquity of BF (including all legendary hominids) is fascinating.

to me, this raises the possibility that BF legends are tied to our deep psychological need to have an "other" who is almost human in our culture and folklore in order to help societies and individuals define what "truly/fully human" is. it can also be helpful to have "monsters" abounding in the wilds outside the village physically (and/or outside the tribe socially) for use in cautionary tales and morality parables told to children, particularly in pre-literate societies. perhaps some of this is even conceivably a cultural memory from coexistence with species like Homo neanderthalensis, Homo erectus, or Homo floresiensis (BIG "conceivably" here)....

so i believe that some of the many BF tales may have been sparked by some real animals, sometime in human cultural memory, but i also believe that "almost humans" may lurk deep in our social histories and yet have not been a part of this physical world for a very long time -if ever. hence the vast worldwide mythology of "near human" sprites and ogres and jinn and "big and little people" and sea-folk and shōjō, and yetis, and trolls, and shape-shifters and all the rest....

it still seems to me that the "legendary non-human hominid" occupies a place in our mental landscape that is distinct from other cryptids, and those very devoted to frequenting this place don't visit the general CZ realm that often.