We all know that the dinosaurs mysteriously (or not so mysteriously) vanished off the face of the earth about 65 million years ago, a mass extinction that still lingers in the popular imagination. How could creatures so huge, so fierce and so successful go down the drain virtually overnight, along with their close cousins, the pterosaurs and marine reptiles? The details are still being worked out by geologists and paleontologists, but in the meantime, here are 10 beliefs about dinosaur extinction that aren't quite true.
1. All the dinosaurs went extinct quickly, at the exact same time.
According to our best knowledge, the K/T (Cretaceous/Tertiary) Extinction was caused by a meteor that plunged into the Yucatan Peninsula in Mexico 65 million years ago. However, this doesn't mean that all the world's dinosaurs suffered an instant, fiery death. The meteor impact raised a huge cloud of dust that blotted out the sun, and caused the gradual demise of a) the earth's vegetation, b) the herbivorous dinosaurs that fed on that vegetation, and c) the carnivorous dinosaurs that fed on the herbivorous dinosaurs. This process may have taken as long as 200,000 years, still a blink of the eye in geologic time scales.
2. Dinosaurs were the only creatures that went extinct 65 million years ago.
Think about it for a second. Scientists believe the K/T meteor impact unleashed a blast of energy equivalent to millions of thermonuclear bombs; clearly, dinosaurs wouldn't have been the only animals to feel the heat. The key difference is, while numerous species of prehistoric mammals, prehistoric birds, plants and invertebrates were wiped off the face of the earth, enough species survived to repopulate the land and sea afterward. The dinosaurs, pterosaurs and marine reptiles weren't so lucky; they were exterminated down to the last individual (and not only because of the meteor impact, as we'll see below).
3. Dinosaurs were victims of the first-ever mass extinction.
Not only isn't this true, but you can make the case that dinosaurs were the beneficiaries of a worldwide disaster that occurred almost 200 million years before the K/T Extinction, known as the Permian-Triassic Extinction Event. This "Great Dying" (which may also have been caused by a meteor impact) saw the extinction of 70 percent of terrestrial animal species and more than 95 percent of ocean-dwelling species. The archosaurs ("ruling reptiles") were among the lucky survivors; within 30 million years or so, by the end of the Triassic period, they had evolved into the first dinosaurs.
4. Until they went extinct, dinosaurs were thriving.
You can't make the case that dinosaurs were on top of their game when they bit the Big Cretaceous Weenie. According to a recent analysis, dinosaur radiation (the process by which species adapt to new ecological niches) had slowed down markedly by the middle of the Cretaceous period, the result being that dinosaurs were far less diversified at the time of the K/T Extinction than birds, mammals, or even prehistoric amphibians. This may explain why the dinosaurs went completely extinct, while various species of birds, mammals, etc. managed to survive into the Tertiary period.
5. Some dinosaurs have survived down to the present day.
It's impossible to prove a negative, so we'll never know, with 100 percent certainty, that absolutely no dinosaurs escaped the K/T extinction. However, the fact that no dinosaur fossils have been found dating from later than 65 million years ago--combined with the fact that no one has yet encountered a living Tyrannosaurus Rex or Velociraptor--is solid evidence that the dinosaurs did, indeed, go completely kaput. If you want to get technical about it, though, we do know that birds are descended from small, feathered dinosaurs, so the continued survival of pigeons, puffins and penguins may be some small consolation.
6. Mammals survived the K/T Extinction because they were "more fit" than dinosaurs.
This is an example of the circular reasoning that plagues students of Darwinian evolution. There's no objective measure by which one creature can be considered "more fit" than another; it all depends on the environment they live in. Until the K/T Extinction Event, dinosaurs fit extremely well into their ecosystem, with herbivorous dinosaurs dining on lush vegetation and carnivorous dinosaurs dining on the herbivores. In the blasted landscape after the meteor impact, small, furry mammals suddenly became "more fit" because of the drastically changed circumstances (and drastically reduced amounts of food).
7. The dinosaurs went extinct because they became "too big."
This one has some truth to it, with an important qualification. The 20-ton titanosaurs living at the end of the Cretaceous period would have had to eat hundreds of pounds of vegetation every day, putting them at a distinct disadvantage when plants withered and died from lack of sunlight (and also crimping the style of the multi-ton tyrannosaurs that preyed on the titanosaurs). But dinosaurs weren't "punished" by some supernatural force for growing too big, too complacent and too self-satisfied, as some biblically minded moralists continue to claim.
8. The K/T meteor impact is just a theory, not a proven fact.
What makes the K/T Extinction such a powerful theory is that the idea of a meteor impact was broached (by the physicist Luis Alvarez) based on other strands of physical evidence. In 1980, Alvarez and his team discovered traces of the rare element iridium--which can be produced by impact events--scattered around the world in geological strata dating to 65 million years ago. Shortly afterward, the outline of a huge meteor crater in the Chicxulub region of Mexico's Yucatan Peninsula was discovered, which geologists dated to the end of the Cretaceous period. This isn't to say that a meteor impact was the sole cause of the dinosaurs' demise (see below), but there's no question that a meteor impact did, in fact, happen!
9. The dinosaurs were rendered extinct by insects/bacteria/aliens.
Conspiracy theorists love to speculate about events that happened millions of years ago--it's not like there are any living witnesses who can contradict their theories. While it's true that disease-spreading insects may have hastened the demise of the dinosaurs, after they were already weakened by cold and hunger, no reputable scientist believes that the K/T meteor impact had a lesser effect on dinosaurs than million of pesky mosquitoes or new strains of bacteria. As for theories involving aliens, time travel or warps in the space-time continuum, that's grist for Hollywood producers, not serious, working scientists.
10. Humans can never go extinct the way the dinosaurs did.
We Homo sapiens do have one advantage that the dinosaurs lacked: our brains are big enough that we can plan ahead and prepare for worst-case contingencies. Today, scientists are hatching all sorts of schemes to intercept large meteors before they can plunge to earth and wreak another mass extinction. However, this has nothing to do with all the other ways humans can potentially render themselves extinct: nuclear war, genetically engineered viruses or global warming, to name just three. Ironically, if human beings do vanish off the face of the earth, it may be because of, rather than despite, our huge brains!