2. Megalodon
Before we get started, it should be noted that A LOT of otherwise intelligent people believe that megalodon is still out there. In fact, of all the daft things that some cryptozoology enthusiasts are willing to fight you over (dinosaurs live in Loch Ness! The original Iceman was a real Bigfoot! etc etc), this belief is one of the daftest. The widespread belief that 20 meter sharks still patrol the worlds oceans was not helped at all by a false Discovery Channel documentary that aired last year called Megalodon: The Monster Shark Lives. This film was intended only as a piece of light entertainment, with actors playing scientists and some creative special effects work thrown in for good measure (the film even has a disclaimer to support this). The same production company also made one arguing the case for the existence of mermaids. In addition, megalodon is also a Photoshop favourite, largely because its really easy (and fun) to splice a picture of an oversized Great White Shark (Carcharodon carcharias) into pictures of surfers and divers. Heres what we actually know: Carcharodon megalodon was a 20-meter (65 foot) long relative of the Great White (some say Mako) Shark. This much is an undisputed fact, as the shark is known to have actually existed from a wealth of fossil evidence (largely the giant fossilised teeth that could only have come from a truly gargantuan shark). It died out in the early Pleistocene era, (around 1.5 Million years ago) and would have likely lived in warmer waters all over the world, preying on small whales, seals and even giant sea turtles. Megalodon is thought to have become extinct as a result of the climate change that took place in the Pleistocene era, which saw several ice ages wreak havoc upon the earth. Fossil records also indicate that the whales megalodon preyed upon began to gravitate more to the newly expanded polar regions around this time, whilst others still had already died out. Whales, being mammals, adapted to cold waters far more readily than a shark (even a self-regulating laminid like megalodon probably was) ever could. Also, increased glaciations led to an enormous drop in sea level, which cant have helped matters much. These theories are strongly supported by megalodons first gradual, then abrupt, disappearance from the fossil record, exactly as all of this was going on. Proponents of megalodons continued existence often argue that the beasts enormous teeth have been found in deep water (and in a non-fossilized state, no less). Furthermore, they also claim that the teeth have been dated and found to be only 10,000 11,000 years old. This evidence is actually a total fallacy; the entire dating method applied to these teeth is unreliable due to the conditions in which they were preserved (its all very science-y), but they are certainly much older than their reported 10,000 years. The discovery of these teeth in the deep ocean has led to a theory that the giant shark may have retreated to deeper, colder waters in order to survive. Put simply, no it didnt. Megalodon evolved in warm (usually costal) waters and died out because the climate change negatively affected its feeding and breeding habits. For megalodon to even have attempted a polar habitat change would be the equivalent of dropping a tropical fish from a heated fishtank into a glass of chilled water from the fridge; instant death. By comparison, Great White sharks today generally live in warm waters, such as the areas around Australia, South Africa and South America. They hunt in the shallower areas along coastlines and although they are comfortable living as deep as 250 metres (820 feet) down, that is a far cry from the icy depths that megalodon is said to inhabit. It is true, however, that Great Whites (like salmon sharks, mako sharks and porbeagle sharks) keep their body temperature a few degrees higher than the water around them, which helps them master some colder waters around the world. They do this with the help of a pretty hefty caloric intake, which is partly why they like eating blubbery seals so much. However, Great Whites do not like extreme temperatures or depths and, although animal adaptation can do amazing things, the belief that megalodon survives in the same fashion by munching on whales really does strain the boundaries of both scientific understanding and common sense. Large, predatory animals that do inhabit the deep ocean are highly specialized and adapted to do so. The largest shark that inhabits cold water is our old friend the Sleeper Shark, a scavenger and opportunistic predator of the deep (that benefits from a naturally occurring antifreeze-like enzyme in its blood. Megalodon was much, much bigger and would require an awful lot more food than sleeper sharks, or even great whites, do. If megalodon was found to be living in cold, abyssal depths, it would pretty much re-write everything we know about animal evolution in one fell swoop. There is simply no habitat, no food source and, perhaps most importantly, no actual evidence for the continued existence of Carcharadon megalodon. These creatures were big, colossal in fact, so it hardly seems likely that they would have gone un-noticed for this long. Even giant squid wash ashore from time to time, why no giant sharks? In 2013, Daniel Holstein, from the University of Miamis Rosensteil School of Marine and Atmospheric Science, told investigative blogger Christie Wilcox that there was absolutely no way that megalodon could have survived. "There's about as much scientific controversy about the possibility of Megalodons lurking in todays oceans as there is about mermaids. None. he said, decisively. Can we let it go now, YouTubers?