Nearly a century ago, the ichthyologist David Stead recorded a strange unease among the lobstermen of Port Stephens, Australia. Although their livelihoods depended on the sea, the men could not bring themselves to venture out to their favorite crayfish spot near Broughton Island for fear of what they had just seen.

Out there, Stead related almost half a century later in his book Sharks and Rays of Australian Seas, was a monstrous, ghostly white shark of such mind-boggling size that apparently no one could agree exactly how big the leviathan was. The shark was big enough to swallow lobster pot after lobster pot, at the least, but the size estimates Stead drew from the workers ranged from 115 feet to an “absurd” three hundred foot minimum. Despite this, Stead argued that the lobstermen must have seen something amazing. “[B]ear in mind that these were men who were used to the sea and all sorts of weather,” Stead wrote, “and all sorts of sharks as well.” There could only be one explanation for such an awful sighting, he concluded. This shark, which Stead believed to be of the “White Death type”, was a remnant of a very real species that sculled the seas for millions of years. This was the shark paleontologists now know as Carcharocles megalodon. Ending on an ominous note, Stead concluded “While they are probably not abundant they may yet be so.”

Carcharocles megalodon was a real shark.* Adults of the species could reach more than fifty feet in length, and their kind sculled the ancient seas for an amazing span – about 16 to 2 million years ago. But there are some who insist that C. megalodon still lives. Ichthyologists and natural history writers from Peter Matthiessen to Richard Ellis have toyed with the idea, not to mention horror novelists and filmmakers who needed a ready-made monster. Even the now-disreputable Discovery channel has gotten in on the act, concocting a new fauxumentary filled with fake evidence that C. megalodon has survived to this day. As paleontologist Thomas Holtz, Jr. remarked, at least this is a minor improvement over the network’s Mermaidsthe network’s Mermaids in that C. megalodon really did exist.

The fossil record for C. megalodon peters out in sediments about 2 million years old. The only teeth so far found in younger deposits have been reworked from older strata. Furthermore, there are no giant, fresh teeth littering the seafloor, no whale carcasses with distinctive bite marks washing up on shore, and no tangible evidence whatsoever that the shark exists. And all the stories… are just stories. Tales such as those Stead shared are not evidence that C. megalodon or other monster shark lives.

Think about Stead’s account. The passage is a memory that a group of people said they saw something on which very few details could be agreed. We are left with the unknown observational skills and uncertain integrity of the fishermen and what Stead was able to recall decades after the fact. The case boils down to “Someone said they saw something.” And the fact that C. megalodon preferred warm, coastal seas is a strike through the notion that the shark is hiding in the deepest depths – if the giant shark became a deep sea predator in the last 2 million years, it’d now be a very different shark from the whale hunter it once was. The thought that the huge shark escaped extinction is tantalizing, but the case itself is not in the least compelling.

*[A note on nomenclature. I know the shark is popularly called Megalodon, but there’s actually a genus that already bears that name. As paleontologist Julie Reizner pointed out to me, Megalodon is a fossil bivalve. My inner paleontological pedant is tickled when hyped documentaries gasp at the thought of a “100 foot Megalodon” – such statements only make me think of titanic shellfish.]

Prehistory’s giant predatory shark is just one variety of sea monster that has garnered the continued attention of cryptozoologists – often self-styled experts dedicated to finding “hidden” animals such as Sasquatch, the Loch Ness Monster, the Chupacabra, and other large, weird, and upsetting animals that have a knack for living just out of reach of our investigations. When I was a kid, I wanted to be one of these explorers.

View Images Abominable Science by Daniel Loxton and Donald Prothero.

The Loch Ness Monster, especially, dug into my imagination because of photos that seemed to show the distinctive flippers of a long-necked, four-paddled animal akin to a plesiosaur. I read every single monster book in my school and local libraries looking for more information, and drew dozens of renditions of what I thought Nessie really looked like. And, in time, I realized that all the accumulated “evidence” for such a creature was faked, misunderstood mundane phenomena, or nothing more than tall tales. The flippers that so convinced me as a child were the worst of all. I had no idea the photos had been artistically altered to look like plesiosaur flippers – the original shots show nothing but bubbles and murk. I really wish I had a book like Daniel Loxton and Donald Prothero’s Abominable Science back then.

Strange as it may seem to say about a book that primarily debunks the purported existence of Sasquatch, the Yeti, Nessie, sea serpents, and Mokele Mbembe, Abominable Science is a loving tribute to monsters that we wish to exist. The key is that Loxton and Prothero, in tandem, spend a great deal of time tracking how we’ve actually created these monsters. Explorers who misunderstood the local lore of people from African jungles to the Himalayas gave rise to new myths, and even classic monster movies – King Kong foremost among them – had a hand in inspiring tales of aquatic enigmas. It’s no coincidence that the account which established the canonical image of Nessie almost exactly matches a scene from King Kong, especially since the story was passed around just after the movie debuted.

In debunking each chosen case, Loxton and Prothero mix personal testimony with deep historical scholarship. Whereas Prothero pulls back the curtain on how shows like MonsterQuest are shams that try to doctor scenes and obscure the questionable credentials of their star experts, Loxton uses his experience as a shepherd to show how your eyes – and mind – can play tricks on you in even familiar surroundings. Seen out of the corner of your eye at the right time of time, an inanimate stump might seem to be Bigfoot, while what seems to be a dog at the edge of the herd can turn out to be a mother grizzly and her cubs. Matched with the historical breakdowns of where monstrous myths come from and how they’re disseminated, the personal accounts will undoubtedly assist readers in developing a well-functioning bullshit detection kit.

If the book has any flaw, it’s that Loxton and Prothero can sometimes get a little lost in the nitty gritty of their arguments. The book’s friendly tone temporarily dries up in the sea serpent chapter during a prolonged discussion of how images of imaginary hippocamps – solely artistic inventions that were half horse, half fish – were incorporated into descriptions of marine monsters, and the final chapter on the nature of paranormal belief loses some of the book’s warmth to a more textbook feel. But, to some extent, this is difficult to avoid. Cryptozoology is based on blurry photos and exciting encounters, whereas the science and historical detectivework behind the legends must take a more careful and staid approach in order to successfully debunk nonsense. In the end, Loxton and Prothero show that “cryptozoology” done properly and with a skeptical eye is not much different than zoology. The search for cryptids ballyhooed in books and basic cable programs is entertaining, but typically relies more on wishful thinking than science.

Yet Abominable Science isn’t solely about monsters. Cryptozoology acts as a foil to introduce readers to the basics of skeptical inquiry and argument. And such a book is sorely needed given how Loxton and Prothero ably demonstrate how easily we can fool ourselves. In an example relevant to sightings of giant sharks, sasquatch, and other aberrations, consider a tale related in the book’s sea serpent section. In 1881, Captain J.H. Taylor recounted how “an enormous monster”, more than one hundred feet long, was seen snaking into India’s Madras Harbor. Onlookers could swear they could see the beast’s hair and eyes. The military scrambled to bombard the threat, only to find that they had just attacked a huge chunk of seaweed. Even people in authority, who we might consider as trustworthy and upstanding, can be easily fooled.

The greatest strength of Abominable Science is the toolkit the book presents for examining extraordinary claims. Readers need not be enamored with monsters to gain a better standard of evidence evaluation from the book. Cryptozoology may be mostly harmless, but it could be a sign of pernicious problems.

Does it really matter that people go out into the woods on a regular basis looking for Sasquatch or spend hours hoping that the head of Cadborosaurus will break the waves off British Columbia? Not really. Belief in the Yeti and similar creatures is absurd, as Loxton argues, but not directly harmful. Yet I’ve also argued Prothero’s point that the pervasive belief in cryptids and associated phenomena can be symptomatic of how much our culture is led by gut feelings and intuition rather than thinking about evidence. Even a documentary that is totally fake, and even admits that it’s a fabrication, can convince many viewers that mermaids are real for no other reason that “much of the ocean is unexplored.” Thought stops there.