Could megalodon Still Live?
Could the Carcharodon megalodon (the giant shark that lived almost 15 million years ago) still be alive in our oceans?
From: U. M.
Whether the giant shark known as megalodon could still survive in the ocean today is a subject of perpetual fascination.
Unfortunately for those who want so desperately to believe, there is absolutely no evidence that the so-called Mega-Toothed Shark (Carcharocles megalodon) survives into the present day. Based on the best available evidence, megalodon became extinct about 1.6 million years ago, at the end of the Pliocene Epoch.
Every now and then, one reads or hears tired old stories of a supposedly fresh, unfossilized megalodon tooth turning up. These stories are false, based on the incorrect assumption that -- simply because a megalodon tooth is not dark and obviously fossilized -- that it must have been lost relatively recently. In fact, fossil megalodon teeth can be almost any color: black, brown, grey, blue, green, red, orange, pink, yellow, to almost white, the color depending upon the precise chemistry of the sediment into which the tooth was deposited.
There are persistent reports of fossilized megalodon teeth -- found inside deep-sea manganese nodules -- that are only 11,000 or so years old. These stories, too, are based on faulty assumptions -- in this case, about the average rate of manganese dioxide accumulation around a nucleus formed by a megalodon tooth. The rate of manganese oxide deposition is highly variable, tied in complex and as-yet poorly understood ways to such factors as oceanic dissolved metallic ions such as iron and fluctuating rates of primary productivity (carbon-fixing through photosynthesis) by phytoplankton. Thus, the purported ages of such manganese nodules are unreliable.
It has often been suggested that megalodon may survive in the deep-ocean, feeding on enormous squids as do certain whales. Based on the fossil evidence, megalodon was exclusively an inhabitant of warm, shallow coastal areas. The deep-sea is a very different and extremely difficult environment in which to eke out a living, requiring all manner of highly specialized adaptations. For example, the deep-sea is uniformly very cold -- often very near freezing -- requiring temperature and pressure insensitive enzymes (protein catalysts) to carry out such vital functions as muscle activity and breaking down food in the digestive tract. That a decidedly warm-coastal inhabitant like megalodon could suddenly develop such adaptations runs contrary to everything we understand about evolutionary processes.
Lastly, persistent stories of encounters with gigantic sharks give some people hope that megalodon still lives on in relatively shallow waters. Such stories do not constitute scientific evidence and some of the lengths reported -- more than 30 metres or 100 feet -- absolutely strain credulity. Assuming that megalodon -- like present-day sharks -- breathed by way of gills, it is highly doubtful that gill surface area (which increases as a square of dimensions) could keep up with the oxygen demands of body volume (which increases as a cube of dimensions). Besides, if megalodon still survived in relatively shallow waters, there can't be just one of them. A whole population of megalodons would wreak havoc on international shipping and coastal recreation. Clearly, this has not occurred. Such a population would also produce and shed tens or hundreds of thousands of fresh megalodon teeth into the marine environment. Yet not a single unfossilized megalodon tooth has ever been found.
There is -- I must admit -- a very, very, very slight chance that the Mega-Toothed Shark known as megalodon could still survive somewhere in today's ocean. But there is absolutely NO physical, scientifically-testable evidence to support such a fantasy. Scientists tend to prefer explanations that are the simplest needed to explain all the observed facts. Rather than speculate on the continued existence of a gigantic shark that has somehow sidestepped the processes of evolution to arrive in our time yet managed to elude human attention or leave any evidence at all that it exists, it is far, far simpler to regard megalodon extinct.
There are those who would regard the extinction of megalodon as a tragic loss, that our planet is somehow less wonderful for this great shark's passing. But I am not among them. If the history of life on Earth has taught us anything, it is that -- fundamentally -- species continually come and go. The sharks we have today -- from the wonderfully bizarre hammerheads (family Carcharhinidae) and tiny, glow-in-the-dark lanternsharks (family Etmopteridae) to the gigantic, plankton-grazing Whale Shark (Rhincodon typus) to the awesome splendor of the mighty Great White (Carcharodon carcharias) -- are plenty spectacular enough for me.
Fantasies can be harmless and a lot of fun, but those of us who can appreciate things as they really are can count ourselves among the very luckiest of people.