Most of what we see today is a very ‘nuts and bolts’ approach to the origin of bigfoot. Basically that in remote (and sometimes not so remote) places on our planet, there are large bipedal hairy organic creatures roaming around, sometimes, but not often, coming in to contact with humans.
The Bigfoot-Giganto Theory
Most popular in this direction is the ‘The Bigfoot-Giganto Theory’, that Bigfoot is a Gigantopithecus, a large ape like creature believed to be last found in Asia some 300,000 years ago. Those creatures crossed the Bering Land Bridge and inhabited North America, evolving into modern day Bigfoot. Little is known about the Gigantopithecus, as only teeth and some jawbones have ever been confirmed to belong to them.
Similar to ‘The Bigfoot-Giganto Theory’ is the ‘Paranthropus Theory’, that Bigfoot is the descendant of Paranthropus, a genus of bipedal apes that evolved in Africa from the Australopithecines, which is the same ancestors from which humans are thought to have come from. This theory ties human’s past much closer Bigfoot’s, explaining the bipedal nature of Bigfoot and similar feet.
Could it be possible that Bigfoot is a surviving Neanderthal? Neanderthals are a species of thought to be extinct humans in the genus Homo, possibly a subspecies of Homo sapiens. They are closely related to modern humans, differing in DNA by only a third of a percent. First showing up on earth about 600,000 years ago, recent fossil evidence puts them still around for sure as recent as 30,000 years ago, coexistencing with humans and most likely crossbreeding. While the Hollywood version of Neanderthal is fairly human like, its believed they were quite difference in appearance and closer to many descriptions of modern Bigfoot than modern humans. You could add that Bigfoot is a ‘Neanderthals on human’ love child as a possibility to this theory and that Bigfoot just happened to leaned more towards the Neanderthal side of the family tree.
Beyond the ‘nuts & bolts’ theories we get into the weird, that Bigfoot is not a flesh and blood creature as we know it, but something much… weirder.
Bigfoot is an Alien
The Bigfoot & UFO connection is well documented. There are multiple cases of both being seen short periods of time.
Bigfoot is a Multidimension Creature
This covers the ‘Bigfoot is a Native American spirit theory’, some reports of Bigfoot becoming invisible during sightings and great tales like the ‘Lawrence Livermore National Labs Bigfoot story‘, which includes Stephen Hawkings, the 4th dimension,and UC Berkeley.