A personal opinion I felt like sharing.
I know cryptozoologists theorize on bigfoot/sasquatch being a descendant of gigantopitheus, but it'd be impossible for a species to suddenly evolve bipealism in just the span of tens of thousands of years (That'd take millions at most).
More likely if Bigfoot existed, I would see it as a hominid, a member of the Australopithecine family. At some before modern homo sapiens evolved (We first appeared 200,000 years ago), a genus of that family (Australopithecines) migrated out of Africa and spread across the world as our prehistoric ancestors had during the last Ice Age overtime growing to becoming bigger (7-8 feet, 600-800 pounds on average), eventually becoming what we would know of many hominid cryptids such as bigfoot/sasquatch, yeti and yowie.
In all honestly, kinda surprised amongst the cryptozoology community, this theory ain't brought up more often...