I was disappointed to read Dr. Karl Shuker's article on megalodon survival in Wild About Animals 12 (2). His continued insistence that megalodon may still survive lacks all reason. The following comments rely heavily upon my paper in the Autumn 1998 issue of The Cryptozoology Review (vol. 3 no. 2: 14-24), entitled "A Critical Evaluation of the Supposed Contemporary Survival of Carcharodon megalodon" (including complete references to support my arguments). Despite being aware of this paper, Dr. Shuker has evidently chosen to largely ignore it, dismissing my points in a breezy manner, and not once mentioning my involvement with the subject. I wish to inform the readers of Wild About Animals of just how unlikely megalodon survival is.
Dr. Shuker's use of a few eyewitness sightings to help build the case for megalodon survival is fatuous. If we are to believe that these sightings indicate that megalodon may still be alive, then the hundreds recorded for the Loch Ness monster and sasquatch should be enough to write up a scientific description of each and justify governmental funding to support formal research expeditions to Scotland and the Pacific Northwest. Given Grey's published report, I am reasonably confident that that the sharks seen were whale sharks (Rhincodon typus). Loren Grey's assertion that what he saw was not a whale shark is hard to believe given that he wrote that the whale shark has "large brown spots and [a narrow] head." In reality, whale sharks have white spots, and have a very wide, prominent head. As for the fabulous tale from Australia of a 150-300 ft long, all-white shark, I find it a hard pill to swallow. The size of the creature--even given exaggeration due to shock--is so enormous that it is hard to believe. In any case, despite the actual identities of the sharks spotted, the fact remains that there are only a few, questionable eyewitness accounts to go on. Anecdotal evidence, by itself, is unacceptable to verify or be suggestive (to the extent that Shuker is) of the survival of an extinct animal.
Dr. Shuker clings to the datings by Dr. W. Tschernezky of two teeth dredged from the Pacific as evidence for his theory. He writes: "[I]t has been suggested that the two Pleistocene teeth were dated inaccurately, but there is no evidence to support such a claim." In fact, the wide consensus today among shark biologists and paleontologists is that the teeth were reworked from older deposits, and then redeposited in much younger sediments. They believe this because megalodon teeth are relatively common until the end of the Pliocene (about 1.5 million years ago--the time at which scientists believe the giant shark went extinct), and then suddenly become extremely rare afterwards. Paleontologists look on such evidence as good grounds for inferring the extinction of an animal. Sharks lose hundreds of teeth each year, so if megalodon were still alive we would expect to find many teeth in post-Pliocene deposits. We don't.
Furthermore, Tschernezky only used the lower value of the manganese dioxide deposition rates to obtain his age estimates. By using the higher values for manganese deposition, one obtains dates for the teeth at 1214 years old and 2600 years old, respectively. It is a mystery that Dr. Shuker and other proponents of megalodon survival have never seized upon this fact to help support their claim. They would be in error to do so, however, as the large discrepancy in dates caused by the rather wide range of possible depositions of manganese is indicative of the unreliability of this method of dating. For example, if one found a hypothetical megalodon tooth that had a layer of manganese 50 mm (2 inches) thick, the approximate datings for that tooth would be 333 000 years old for the maximum age (the way Tschernezky did it) and 36 000 years old for the minimum age. The difference between those two dates is 297 000 years. Utilizing the higher value consistently gives a date representing only 10% of that of the lower value. Such a large range of error is hard to accept and thus dating by rates of manganese deposition is inaccurate and unreliable.
Finally, a fundamental flaw in Tschernezky's findings lies in his use of manganese dioxide as an indication of geological age. Manganese dioxide deposition is far from constant, varying due to fluctuations in the concentrations of ions of iron (especially Fe2+) and other elements in sea water. The presence of phytoplankton also plays a factor in the rate of manganese dioxide deposition, partly because Fe2+ is a key ingredient in photosynthesis. Therefore, when a plankton bloom occurs---often caused by an increased concentration of Fe2+---more Fe2+ is removed from the sea water (often remaining removed for many years) and less is available for deposition.
Dr. Shuker writes: "Sceptics counter-claim that megalodon was not a deep sea fish but a coastal, near-surface dweller (which means that it would surely have been seen more frequently if still alive). But as the megalodon is known only from its fossil teeth and a few vertebrae, it is impossible to say with certainty where it lived." With that, Dr. Shuker does a great disservice to the enormous amount of valuable work done by shark paleontologists over the years. He also contradicts himself, writing only a few paragraphs before that "According to Dr. John Clay Bruner from [the University of Alberta], megalodon inhabited warm seas worldwide 24-1.67 million years ago..." As Bruner told him, it is widely accepted that megalodon was a continental shelf inhabitant of tropical and sub-tropical waters. There is no evidence suggesting that it was a deep sea creature. In fact, megalodon was quite ill-suited for the deep sea, being a large, active predator of whales (at least in a scavenging capacity) and large fish, much like the modern-day great white shark (Carcharodon carcharias). The deep-sea is a harsh environment, with sporadic food sources, cold temperatures, and high pressure; the animals that live there have many adaptations to deal with these stresses, including temperature and pressure insenstitive enzymes, lowered metabolisms and reduced skeletal and muscle development. As a near-shore surface dweller, megalodon almost certainly had none of these specializations. To assume that megalodon had or could have evolved the intense physiological specializations of deep-sea animals is extremely unlikely. From the available evidence, it makes far more sense to concede that megalodon is extinct; certainly, this represents better science than the invention of a fabulous evolutionary adapatation to the deep-sea.
The plain fact of the matter about megalodon survival is that no scientist involved with shark biology or paleontology would suggest that the big fish still exists. The reason is quite sensible: there is no worthwhile evidence and the idea does not fit in with actual, well-documented scientific knowledge. Until cryptozoologists like Dr. Shuker control their attempts to resurrect any number of prehistoric, extinct animals to explain various cryptids--for which there is often little evidence--they cannot hope to receive mainstream acceptance from scientists.
Ben S. Roesch
Copyright 1999 Ben S. Roesch