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Why Bigfoot is Unlikely Only If You Know What “Unlikely” Means

The views expressed are those of the author and are not necessarily those of Scientific American.

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What we don’t know is shaped by what we do. Whatever dark matter is, we will look for it assuming an accelerating, expanding universe. However cancer can be truly defeated, we will have to outsmart evolution to do so. And no matter what bizarre creatures are still to be discovered in our densest forest and deepest ocean depths, they are unlikely to ever be Bigfoot, Nessie, or the Chupacabra.

We have found monsters before. As biology has gotten better at tracking down the beasts that elude us, unlikely legends are becoming real animals. Just recently, we finally obtained amazing footage of two very mysterious creatures—the giant squid and the oarfish. They didn’t appear from nowhere either. Over the years biologists and fisherman have found traces of their existence, from fins and tentacles to intact bodies. This is how we find rare creatures in huge areas—we follow the evidence.

Cryptozoological creatures like Nessie and Bigfoot are both (supposedly) large animals living in large areas, and both have decades of “evidence” to suggest that we might film one someday—as we did the giant squid. But practicing biologists still consider these mythic animals’ existence to be highly unlikely. Why? In science, the kind of evidence matters; all unlikelihoods are not created equal.

The methods of science lay out a continuum of knowing, from plain ignorance and necessary uncertainty, to likely truths, to facts so well established “that it would be perverse to withhold provisional assent,” as Stephen Jay Gould famously said. For peer review, replication, and objectivity to make any headway on the continuum, for science to find the right answers to anything, there have to be wrong—or at least unlikely—answers. It’s how we know that vitamin C doesn’t cure the common cold and multi-vitamins are for the most part useless, for example. By blinding, replicating, and ultimately verifying experiments, science moves forward.

It’s possible to move backwards on the continuum as well. The more personal data gets—the more the evidence is anecdotal and neither repeatable nor verifiable—the less likely a theory becomes. Anecdotal support like stories and sightings don’t determine impossibility, but frankly, a body is always better. That is something others can measure and touch; nobody can see exactly what you saw. The fallibility of anecdotal and eyewitness support is why it is very unlikely (if not impossible) that a large ape-human hybrid roams the world’s deep forests and that the Loch Ness is anything other than barren. If that is the true state of Nessie’s and Bigfoot’s biology, how can their existence be so commonsensical in our culture?

Daniel Loxton, co-author with Donald Prothero of the fantastically thorough new book Abominable Science!: Origins of the Yeti, Nessie, and Other Famous Cryptids [Amazon], contends that cryptozoologists don’t assess probability in the same way scientists do, and as a result they get their science backwards. In an email exchange he told me:

A scientist generally starts with the conservative working assumption that proposed new ideas are not true or that hypothetical new entities do not exist, and then revises her probability estimate upwards only when the evidence forces her to do so. A pseudoscientist typically starts with the assumption that a novel proposal seems to be true, and then revises her probability downward as the evidence leaves her no choice—if she is willing to surrender the possibility to any degree at all.

In fact, Loxton went on to tell me, he is unaware of any cryptid, such as Bigfoot or Nessie, or class of evidence that has been abandoned by the cryptozoological community altogether—despite the well-publicized hoaxes and incompatible ideas.

Ultimately, whether an idea in any field of inquiry is unlikely or not depends on the standard of evidence. Here zoology and cryptozoology part ways. Science—psychology in particular—has shown time and again that human perception is easily distorted, and therefore plain eyewitness testimony in biology or zoology holds little weight. In contrast, pseudoscientific endeavors like the continued hunt for Bigfoot use each new eyewitness “sighting” to increase the likelihood just a little. Innumerable eyewitness reports amount to a “likely” conclusion in Bigfoot lore because the existence of Bigfoot was decided upon before it was seen.

Anecdotal and eyewitness data have a fatal flaw—enough stories and sightings can actually make a mythical creature less likely to exist.

Consider Bigfoot. It goes by many names—over 100 by some counts. It supposedly lives on every continent except for Antarctica…in sustaining populations. It should be everywhere. The ubiquity of Bigfoot sightings smashes up against the fact that we have never found any verifiable scat, bones, hair or body. We sometimes hook giant squid—a creature we apparently see far less often than Bigfoot that occupies a much larger area—but a hunter never shoots a Sasquatch. Paradoxically, Bigfoot has been reported too many times to actually exist.

With a different perspective on what “unlikely” means, when science considers the existence of Bigfoot or Nessie or UFOs or psychic powers unlikely, it can be like the denial of  “a rock solid established fact, like the existence of France,” to believers, Loxton says. And if you don’t know how the scientific continuum moves, then what “unlikely” means really can be foreign. It certainly feels foreign to value biological theories over “I know what I saw” narratives, says Loxton. “It’s the way we’re built.”

Cryptids persist because “unlikely” means something else to their proponents—the same things that make Bigfoot scientifically unlikely are lauded as nail-in-the-coffin positive evidence for squatchers. Biologists and cryptozoologists interpret unlikelihoods differently enough that a deeply flawed study of “Bigfoot DNA” can be interpreted to say that Bigfoot is both scientifically unlikely and too likely not to exist at the same time.

There are still monsters out there. Some are based on myth and word-of-mouth, others on body parts and dredged decompositions. As long as biology and cryptozoology keep talking past each other, each with their own language of unlikely, what kind of evidence do you think will help us find the next monster?

Image Credit:

From the exhibition Cryptozoology: Out of Time Place Scale, as shown at the Kansas City Art Institute’s Artspace by Kelly Garbato on Flickr

Bigfoot by Marc Dragiewicz

Kyle Hill About the Author: Kyle Hill is a freelance science writer and communicator who specializes in finding the secret science in your favorite fandom. Follow on Twitter @Sci_Phile.

The views expressed are those of the author and are not necessarily those of Scientific American.

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  1. 1. SteveinOG 1:54 pm 10/1/2013

    One thing worth mentioning is that many people earn a living off of sustaining the belief in cryptozooids. They are not simply using a different standard of evaluating evidence, but are perpetrating myths because that is how they get money.

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  2. 2. SAROB 2:11 pm 10/1/2013

    Decent and necessary article by Mr. Hill.

    As he points out, it is important to remind those interested in Crypids that repeatable, measurable evidence is how science moves forward.

    Thinking outside the confines of physics and empirical evidence is only for the imaginative, risk-taking types
    who usually suffer the tongue-lashings of rulers and believers of the status-quo. People like Tesla, Galileo and perhaps,eventually, Grover Krantz and Jeffrey Meldrum were not recognized for their contributions to science until long after they were gone. Maybe a Bigfoot body will appear soon, and make this argument moot.

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  3. 3. Silkysmom 2:16 pm 10/1/2013

    We don’t know everything about everything. I have never seen a Bigfoot. I have never seen a radio wave either but I am listening to my radio right now.

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  4. 4. hicks.daniel.j 2:24 pm 10/1/2013

    Loxton’s generalization about “scientists” and “pseudoscientists” is bad history and philosophy of science. In the history of science, innovative hypotheses are often accepted with great enthusiasm by many scientists on the basis of inconclusive experiments and persuasive but incomplete data, not “only when the evidence forces [them] to do so.” Harry Collins and Trevor Pinch give several examples in their book /The Golem/, including general relativity. The Michelson and Morley experiments, for example, provided evidence against ether theories and physical distortion theories, but did not logically entail that these kinds of theories are all false.

    As for philosophy, on a standard Bayesian account, individual scientists are free to set their initial or prior subjective probabilities as high or low as they like. Bayesians argue that, as evidence is accumulated, so long as everyone updates their probabilities in accordance with Bayes’ theorem, they will eventually converge to the same probability — this is called “swamping the priors” or “washing out the priors.” There’s nothing pseudoscientific about starting with a high prior; nor is there anything scientific about starting with a low prior.

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  5. 5. dada king 4:54 pm 10/1/2013

    The best bigfoot book of all time is “Bigfoot Down” to cool…google it

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  6. 6. smartpatrol 6:27 pm 10/1/2013

    Interesting idea. Is it unlikely crop circles are created by Aliens as well?

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  7. 7. Kyle Hill in reply to Kyle Hill 10:27 pm 10/1/2013

    Sure, but you can prove that radio waves exist through other methods than sight rather easily.

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  8. 8. Jerzy v. 3.0. 10:23 am 10/2/2013

    But, perversely, we know it only because some scientists searched for Loch Ness Monster and found none. So, if no scientist was ever interested in a Loch Ness Monster, its existence would be still a valid scientific possibility*.

    *Actually, there are some undescribed animals whose existence is still open.

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  9. 9. larkalt 1:03 pm 10/2/2013

    There are actually scientists investigating the possible existence of sasquatches. Bryan Sykes, a well-known geneticist, is investigating possible sasquatch DNA samples, and there are sites where people attempt to get sasquatches used to people, and gather evidence. The Erickson group runs one such site and recently released some video from it. So is the Erickson group, whiclh includes biologists, a group hoax? Can you come up with a credible picture where these people are hoaxing each other with videos of a motorized breathing fur suit?
    You have to have some level of belief to put in the effort to do something like that. Many scientists have passionately pursued their own personal theories. Many scientists have pet ideas. The idea that the skeptical position of a priori non-belief is the scientific position, over-inflates the value of skepticism.
    The rigor of science comes more from it being a group effort – scientists can expect to have their theories extensively questioned, their experiments repeated.

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  10. 10. marcringuette 7:48 pm 10/2/2013

    I eagerly followed Kyle’s link from the phrase “multi-vitamins are for the most part useless”, but the linked article didn’t say that at all. It cited some evidence that MEGAvitamins can increase mortality. False advertising, dude!

    Kyle, do you know of any evidence against, or in favor of, a daily multivitamin? The only response to that question that I’ve ever heard is the non-answer that we should all strive for a balanced diet. What a cop-out. I still don’t know if my daily multi is a good insurance policy or not, because I’ve never seen any evidence either way. Grumble.

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  11. 11. marcringuette 8:18 pm 10/2/2013

    To answer my own question, at least partially — the Physicians’ Health Study II Randomized Controlled Trial looks like a good source of info, especially for older men like myself.

    The evidence looks mildly positive for multivitamin supplementation in that group, in at least the cancer and cognitive decline sub-studies.

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  12. 12. freshhawk 8:35 pm 10/2/2013

    If this is the level of scientific understanding on display at in the comments it’s surely time to follow and disable comments (

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  13. 13. jjhorstman 12:29 am 10/3/2013

    I’ve seen one with my own eyes, so assumptions be damned…

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  14. 14. Mendrys 9:33 am 10/6/2013

    Too bad you didn’t have your camera with you.

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  15. 15. hungry doggy 4:41 pm 10/7/2013

    You are taking these crypto monsters way too seriously. There is an element of fun involved in not knowing if Big Foot or if the Loch Ness Monster are real.

    I mean these things probably don’t exist. Just like Santa Claus doesn’t really exist. But we all have fun with the possibility, it makes life more interesting, and we all enjoy telling the stories. Some things are for fun and we ought to just accept them in that spirit. Frankly I’d just as soon keep the story of Big Foot alive and never know for an absolute certainty that he doesn’t exist. Now I’ve got to go make a telephone call to the Easter Bunny. (What, you don’t believe telephones are real?)

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  16. 16. Kyle Hill in reply to Kyle Hill 8:27 pm 10/7/2013

    My point was that it’s bad for science for these ideas to be taken seriously, which in my opinion they are. Look at the programming on The History or Discovery channel. People think these cryptids exist and base that on bad evidence, poor ways of evaluating the world. I think it does a great disservice to lower the bar of belief and retards reasoning skills.

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  17. 17. bucketofsquid 3:45 pm 10/11/2013

    It would be nice if you would use the acronym UFO correctly. Unidentified Flying Object is a reference to any flying object that is not yet identified by the observer. UFOs are typically the moon, unusual aircraft, balloons or frizbees. Any one that doesn’t believe that they might see something in the sky and not know exactly what it is qualifies as an idiot.

    Anyone that wants to refer to alien spacecraft should say alien spacecraft. Technically that isn’t particularly accurate either because an alien is someone from another country so an event where a Japanese rocket returned to Earth and landed in the USA would be an alien spacecraft landing.

    As far as “bigfoot”, I don’t think his feet are very big in relation to his body so wouldn’t it be better to call him “significantly tall with proportional feet” instead?

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