This picture shows Al Hodgson, a volunteer guide at California's Willow Creek-China Flat Musuem, holding up a plaster cast believed by some to be a Bigfoot imprint.
Authentic or not, footprints and other physical artifacts are meaningless scientifically, says Radford, when there is no standard to measure them by.
"Some of the footprints have three toes, some have four toes, and some of course have five," he noted. "Even if I'm certain a certain track wasn't made by anything else, how do I know it's Bigfoot? You can't."
The same goes for DNA. Scientists make a positive identification by comparing an unknown sample to a known one. There is no such standard for Bigfoot, says Radford. Even an educated guess about the giant footprint pictured here or a Blobsquatch gone wild is, at best, a shot in the dark.
Benjamin Radford is the co-author of "Lake Monster Mysteries: Investigating the World's Most Elusive Creatures."