Meldrum, an expert on primate morphology, says the hoax stories don't hold up under scrutiny.
"If you watch the film as a student of anatomy, primates and locomotion, you can see the movement of the shoulder blade under the skin," he said. "I can see the calf muscles contract at the appropriate moments. When anyone tries to replicate it in any way, it doesn't look like a primate."
His theory?
"You can never be 100 percent sure of anything, but beyond a reasonable doubt I am convinced it portrays a real animal," he said. "My working hypothesis is they are a species of great ape restricted to the ground but having an arboreal legacy. They would most likely be related to the orangutans."
Meldrum said the lack of Bigfoot corpses is not a mystery, given the remote spots where they are believed to live as well as the dampness of the forest and the acidic quality of forest soil, which encourages decomposition.
Upstairs in his office, Perez plays the Patterson-Gimlin film on his computer again and again.
He thinks as many as 100,000 Bigfoots could be roaming North America, but he knows he may never find one.
"A lot of early researchers thought we would solve the mystery in a few years, but we haven't," he said. "I can't prove Bigfoot exists, but either someone has been fabricating tracks for over a hundred years or there is a real animal out there."