My hunch is that these sightings of big foot are actually unusual-looking bear. I have seen bear, and not all of them look like the textbook pictures. Sometimes they are quite lean and long legged and look almost like an ape with a dog's head. Some bear have shoulders like a quadruped, and some bear have shoulders more like a biped, or like those of a gorilla. I think maybe it has something to do with the individuals age too. Maybe the younger, underfed ones have more tendency to have the silouette of a primate than the old fat ones do.
I read through about 50 first hand sightings the other night. Everyone described this creature as having Hair not fur. Hands like a human, Big feet ( obviously ) and toes. So I would be agreeing with you except all of these sightings were from the mid 1950s to last week. There are kooks outthere without a doubt, however what is the motivation for 1000's to describe the same creature? I am having to go with the sheer numbers here, and say they must have indeed seen what they claim to have. I just dont know what it is.