Resume Reading — Why We Can’t Rule Out Bigfoot


Why We Can’t Rule Out Bigfoot

How the null hypothesis keeps the hairy hominid alive.

I recently got an email from an anthropologist commenting on a new report in the Proceedings of the Royal Society. The topic of that…By Carl Zimmer

I recently got an email from an anthropologist commenting on a new report in the Proceedings of the Royal Society. The topic of that report was Bigfoot—or rather, a genetic analysis of hairs that people over the years have claimed belong to a giant, hairy, unidentified primate.

The international collaboration of scientists, led by University of Oxford geneticist Bryan Sykes, found no evidence that the DNA from the hairs belonged to a mysterious primate. Instead, for the most part, it belonged to decidedly unmysterious mammals such as porcupines, raccoons, and cows.

My correspondent summed up his opinion succinctly: “Well, duh.”

This new paper will not go down in history as one of the great scientific studies of all time. It doesn’t change the way we think about the natural world, or about ourselves. But it does illustrate the counterintuitive way that modern science works.


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Bigfoot advocates have repeatedly claimed that professional scientists are willfully ignoring compelling evidence.

Since absolute proof was impossible, Fisher preferred to be practical when he ran experiments. At the lab where he and Bristol worked, Fisher was charged with analyzing decades of collected data to determine whether that information could divine details, like the best recipe for crop fertilizer. Scientists could use that data to design ever larger experiments with increasingly more accurate results. Fisher thought it would be pointless to design an experiment that needed centuries to yield results. At some point, Fisher believed, scientists had to just call it a day.

He believed that a sensible threshold was 5 percent. If we assumed that the null hypothesis was true and found that the odds of observing the data was less than 5 percent, then we could safely reject it. In Bristol’s case, the odds were comfortably below Fisher’s threshold, at just 1.4 percent.

Thanks in large part to Fisher, the null hypothesis has become an important tool for scientific discovery. You can find tests of null hypotheses in every branch of science, from psychology to virology to cosmology. And scientists have followed Fisher in using a 5-percent threshold.

Which brings us back to Bigfoot.

to the lab!: Throughout the years, dubious “proof” has been presented regarding the existence of Bigfoot, the Abominable Snowman, yetis, and countless other mysterious creatures. None have been proven to exist, but none have been definitively proven not to exist, either.Wikipedia

People have been claiming they’ve seen hairy humanoids for decades. They’ve offered up grainy photos, ambiguous casts of footprints, and enigmatic clumps of hair. In recent years, they’ve even tried to extract DNA from the hair, but scientists have dismissed these genetic studies because they didn’t involve standard safeguards routinely used in such research.

Bigfoot advocates have repeatedly claimed that professional scientists are willfully ignoring compelling evidence. The problem, in fact, is that the advocates haven’t been approaching the question of Bigfoot in a scientific fashion. So two years ago Sykes and his colleagues decided to run a scientific study of those hairs from an “anomalous primate.” And that involved creating a null hypothesis to try to reject.

The null hypothesis they developed was this: The hairs purported to come from Bigfoot (or the Abominable Snowman or other regional varieties of the creature) belonged not to a previously unknown primate, but to known mammals. They extracted DNA fragments from 30 different hair samples and were able to isolate the same short stretch of DNA from each. They then compared that stretch to the corresponding stretch of DNA sequenced from many living mammals.

The results were clear: The scientists found precise matches for all 30 samples in previously known mammals.

Does this mean Sykes and his colleagues have proved that Bigfoot does not exist? No. It simply means that Sykes, unlike Fisher with his tea test, could not reject the null hypothesis. The question remains open, and—if Bigfoot doesn’t exist—always will.

That’s not to say Sykes’ study didn’t offer its own surprises. Two hair samples from the Himalayas matched a DNA sequence that was extracted from a 40,000-year-old fossil of a polar bear. Stranger still, their DNA was not a match to living polar bears.

In their report, Sykes and his colleagues offer a scenario for how such a result could have come about. It’s possible that ancient polar bears and brown bears interbred, and some living bears in the Himalayas still carry a bit of that ancient polar bear DNA.



And so science carries on, from one null hypothesis to another.

Carl Zimmer is a columnist for The New York Times and the author of 12 books, including A Planet of Viruses.

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