Most people, including scientists, think that pseudo-scientific claims are essentially unfalsifiable, since a skeptic can't typically provide direct physical evidence proving the non-existence of something. But, luckily, pseudo-science proponents sometimes make scientifically testable or falsifiable claims, or at least making claims we can analyze with some serious scientific confidence. Here's an example involving 'squatches that I noticed while watching Animal Planet's Finding Bigfoot television series.
Bigfoot ("sasquatch") believers have estimated that there are between 2,000 and 6,000 bigfoots in North America. Surely, a hairy lumbering 7 to 9-foot-tall giant primate living in modern North America, snooping around at all hours of the day and night in both rural and suburban areas, would have been struck by a motor vehicle by now, right? Not so, according to the Bigfoot Field Researchers Organization (BFRO) FAQ, which claims that this painful lack of evidence is explained away by simply saying "Around humans their typical behavior is to flee or hide. They try to stay out of view or at least in the shadows when near people or moving vehicles." But that behavior describes many, many species of real animals that actually exist and nonetheless end up as highway spaghetti. If bigfoots really exist, where are all the bigfoot roadkills? Let's find out...
Humans are the most intelligent of all animals, and generally of the understanding that it's not a good idea to get in the path of a huge metal box going at a high rate of speed, like a motor vehicle. Nonetheless, human pedestrians manage to get themselves into motor vehicle accidents tens of thousands of times per year, with many accidents resulting in deaths. According to a report by the National Highway Traffic Safety Administration, in 2006 there were 67,573 car accidents involving pedestrians, resulting in 4,784 pedestrian deaths. With the U.S. population right at 300 million people in 2006, this means that 0.0225% of Americans managed to get hit by cars, and 0.0016% died from the incident. These are the annual pedestrian hit rates and the kill rates by vehicles for the human population in the United States.
Next, we can use these to estimate what should be the annual hit and kill rates for the hypothetical bigfoot population in North America. This will tell us how many bigfoot roadstrikes and roadkills we should expect to observe if bigfoots actually exist.
Non-human animals are surely more likely to be killed by vehicles, statistically-speaking, than humans who are intelligent, who build cross-walks, who are taught to look both ways before crossing streets, who typically don't cross freeways on foot, and who build pedestrian pathways to minimize the dangers of automobiles to people. Let's very generously assume that bigfoots are only twice as likely as humans to get hit by cars, since bigfoots are certainly less intelligent and presumably unlikely to be using crosswalks or sidewalks or wearing reflective vests in low-light conditions. Most good-sized animals probably have considerably higher hit and kill rates over humans, likely much much higher than only 2 times the rate of humans (possibly up into single digit percentages or more for some species). But we'll be generous for now and see where the numbers take us. So now we have an estimated annual hit rate for bigfoots of 0.0450% and a kill rate of 0.0032%.
Those rates don't initially sound high, being well under 1%, but let's apply them to the BFRO's population estimates (from 2,000 to 6,000) over the last 60 years and see what we find. If the population of bigfoot has been around 2,000 over the last half century or more, our estimated annual hit rate suggests that there should have occurred at a bare minimum 54 car accidents involving a bigfoot, with at least four involving a bigfoot fatality. If the population is instead 6,000 then there should have been 162 bigfoot vehicle strikes resulting in a dozen bigfoot deaths. Remember these are extremely conservative estimates.
How many bigfoot roadway fatalities have there been? Obviously, none. Zero, zilch, nada. OK, so how many times has a bigfoot been hit by a vehicle that did not result in its death? And what about near-misses? Let's go to the BFRO's FAQ for their own answers to these questions: "Only a very small fraction of the thousands of credible sighting reports describe near-misses with vehicles. No substantiated reports describe a collision with a bigfoot."
But wait! Our extremely conservative estimates based on comparably-sized primates living in similar areas (i.e., humans) over the last 60 years suggest that at the very least, at an absolute minimum, there should have been several bigfoots killed by vehicles, and dozens upon dozens of non-fatal bigfoot vehicle strikes leaving many maimed or wounded bigfoots to be recovered. By the BFRO's own admission, again, no carcasses have been recovered, no crippled or wounded bigfoots have been found, not a single report describes a collision, and there are almost no near-misses reported. Something is wrong here.
Now consider these numbers. There are roughly 400 million animals struck and killed by motor vehicles each year in the U.S. alone. That means over the last 50 years, in the U.S., there were something like 20 billion animal roadkills. And not a single one of those 20 billion carcasses were a bigfoot? How is that possible? Seriously, what are the odds that not a single bigfoot has ever been maimed or incapacitated by a vehicle strike, and there are almost no near-misses reported, and not one bigfoot has been found among the 20 billion animals killed along U.S. roadways in the last half century? Surely any one of these events should have happened by now, but none have. With these probabilities considered together, it's spectacularly and astronomically unlikely that not one of these events has happened yet, if indeed bigfoot truly exists. It's effectively impossible.
This same sort of analysis applies not just to the lack of bigfoot roadkill, but also to the observations that no bigfoot has ever accidentally (or purposefully) been shot by a hunter or caught in a trap; no bigfoot has ever accidentally drowned or slipped on a mountainside or died of natural causes in such a way that their carcass could be discovered by humans; and of course that not a single bigfoot has ever had a clear non-grainy photograph or video taken of it. All of these things, or at least some of them, or even just one of them, should have happened by now. The statistics are clear. The fact that not one of these events has happened yet tells us something important. The inescapable conclusion is that bigfoots don't exist, and we can say this with high scientific confidence.