Why Did the Dinosaurs Die Out?
No one really knows the exact reasons for the extinction of these gigantic reptiles. But many theories have been put forward to account for the dinosaurs’ disappearance at the end of what scientists call the Cretaceous Age. This was about 70 million years ago.
Great catastrophes such as floods, earthquakes and volcanic eruptions producing deadly gas and ash falls have been suggested. But such catastrophes would have had to be almost worldwide since dinosaurs were present on all continents.
Food might have been a problem, vegetation underwent great changes during that period of the earth’s history. Parasites and diseases might have struck the creatures down. Perhaps the dinosaurs, which were up to 80 feet in length and bulky in proportion, were unable to adapt themselves to the changing conditions.
The most plausible explanation may be that there was a great cooling of the climate. This would have affected the big dinosaurs much more than birds and mammals that could regulate their body temperatures.
One early theory was that small mammals ate dinosaur eggs, thereby reducing the dinosaur population until it became unsustainable. Another theory was that dinosaurs’ bodies became too big to be operated by their small brains. Some scientists believed a great plague decimated the dinosaur population and then spread to the animals that feasted on their carcasses.
In 1956, Russian astronomer Joseph Shklovsky (1916-85) became the first scientist to consider the extinction was due to a single catastrophic event when he theorized that a supernova (the explosion of a dying star) showered the earth in radiation that could have killed the dinosaurs. Once again, the problem with the theory was explaining why dinosaurs died out and other species did not. Also, scientists said that such an event would have left evidence on the surface of the earth–trace amounts of radiation dating back to the Cretaceous Period. None was found.
However, in the 1980s, father-and-son scientists Luis (1911-88) and Walter Alvarez (1940-) discovered in the geological record a distinct layer of iridium–an element found in abundance only in space–that corresponds to the precise time the dinosaurs died. This suggests that a comet, asteroid or meteor impact event may have caused the extinction of the dinosaurs. In the 1990s, scientists located the massive Chicxulub Crater at the tip of Mexico’s Yucatán Peninsula, which dates to the period in question.
A definite solution of the mystery of the death of the dinosaurs still seems for distant. It may have been due to a combination of some of the theories given here or of others still unknown. Nevertheless the dinosaurs survived for more than 100 million years. We have been here for only two million years.