quarta-feira, 26 de abril de 2017

Do Dinosaurs Still Roam the Earth?

Why Cryptozoologists and Creationists Believe Dinosaurs Never Went Extinct 

One issue that gives paleontologists (and scientists in general) fits is the impossibility of proving a negative. For example, no one can demonstrate, with 100 percent certainty, that every single Tyrannosaurus Rex vanished off the face of the earth 65 million years ago; there's an astronomically slim chance that some lucky individuals managed to survive, and are happily breeding even now on a remote, and still undiscovered, version of Skull Island.





The same goes for any dinosaur you can name: Diplodocus, Velociraptor, the wishful-thinking list goes on and on.
This isn't simply a rhetorical issue. In 1938, a living Coelacanth--a prehistoric lobe-finned fish believed to have gone extinct at the end of the Cretaceous period--was caught off the coast of Africa. To evolutionary scientists, this was as shocking as if a snorting, snarling Ankylosaurus had been discovered in Siberia, and caused some quick rethinking about the casual use of the word "extinct." (The Coelacanth isn’t technically a dinosaur, of course, but the same general principle applies.)

"Living Dinosaurs" and Cryptozoology

Unfortunately, the Coelacanth mixup has bolstered the confidence of modern-day "cryptozoologists," researchers and enthusiasts (not all of them scientists) who believe that the so-called Loch Ness Monster is actually a long-extinct plesiosaur, or that Bigfoot may be a living Gigantopithecus, among other fringe theories.
Many creationists, too, are especially eager to prove the existence of living dinosaurs, since they believe this will somehow invalidate evolutionary theory (which it won't, even if that mythical Oviraptor is ever discovered wandering the trackless wastes of central Asia).

The simple fact is that, every single time reputable scientists have investigated rumors or sightings of living dinosaurs or other "cryptids," they’ve come up completely dry.


Once again, this doesn’t establish anything with 100 percent certainty--that old "proving a negative" bugaboo--but it is persuasive empericial evidence in favor of the total-extinction theory. (A good example of this phenomenon is Mokele-mbembe, a putative African sauropod that has yet to be conclusively glimpsed, much less identified, and probably only exists in myth.)

Many of these same people also cling to the idea that the "dragons" mentioned in the bible (and in European and Asian folk tales) were actually dinosaurs--and that the only way the dragon myth could have arisen in the first place is if a human being witnessed a living, breathing dinosaur and passed the story of his encounter down through countless generations. This "Fred Flintstone theory" is complete nonsense, of course--for more, see this article about dinosaurs and dragons.

Why Couldn't Dinosaurs Survive Into Modern Times?

Is there any evidence, beyond the lack of reliable sightings, that small populations of dinosaurs couldn't be living somewhere on the earth today? As a matter of fact, yes. It's easiest to dispose of the biggest dinosaurs first: if Mokele-mbembe was really a 20-ton Apatosaurus, that would imply the existence of a sizable population: a sauropod could only live for about 300 years, max, and its continued survival down to the present day would require a breeding population of at least dozens or hundreds of individuals.


If there were really that many dinosaurs roaming the Congo basin, someone would have taken a picture by now!
A more subtle argument relates to the differences in the earth's climate and geology 100 million years ago compared to today. Most dinosaurs were adapted to living in extremely hot, humid conditions, of the type that are found in only a few modern regions--which have yet to produce any proof of living dinosaurs. Perhaps more tellingly, the herbivorous dinosaurs of the Mesozoic Era feasted on plants (cycads, conifers, ginkgoes, etc.) that are extremely rare today. These plant-munchers lay at the base of the dinosaur food chain, so what hopes could there be of anyone encountering a living Allosaurus?

Are Birds Living Dinosaurs?

On the other hand, a question like "Did the dinosaurs really go extinct?" may be missing the point.
Any group of animals as numerous, diverse and dominant as dinosaurs were bound to pass off a huge chunk of their genetic material to their descendants, no matter what form those descendants took. Today, paleontologists have made an open-and-shut case that dinosaurs never really went extinct at all; they merely evolved into birds, which are sometimes referred to as "living dinosaurs."

This "living dinosaurs" motif makes even more sense if you consider not modern birds--which are mostly a tiny, docile lot compared to their distant ancestors--but the gigantic "terror birds" that lived in South America during the Cenozoic Era. The biggest terror bird of them all, Phorusrhacos, measured about eight feet tall and weighed in the neighborhood of 300 pounds--and it also hunted like a middleweight theropod dinosaur of the Jurassic or Cretaceous periods.

Granted, Phorusrhacos went extinct millions of years ago; there are no dinosaur-sized birds alive today. The point is, you don't need to posit the continued, mysterious existence of long-extinct dinosaurs; their descendants are in your backyard today, hopping around the bird feeder!


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