by Mayflor Markusic

Created on: March 31, 2009   Last Updated: April 03, 2009

Based on the fossilized bones that archaeologists unearthed, dinosaurs are gigantic and sometimes ferocious organisms. They didn't just exist, they ruled the surface of planet earth. But suddenly, about 65 million years ago, they disappeared. Something so large affected these powerful creatures that they became extinct. This "something" is the mystery that gave rise to extensive scientific investigations and speculations. Today, there are numerous theories on how dinosaurs became extinct. Five of them will be briefly described here.

Asteroid impact theory -An asteroid, estimated to be nine miles in diameter, hit the earth, specifically the Yucatan peninsula. The impact did not just surprise the dinosaurs. If there were only shock waves, some dinosaurs would have survived today. But the impact led to tidal waves, forest fires, and air pollution. The whole planet became dark, hot, and sinister for these large creatures. They have nowhere to hide.

Greenhouse effect theory -Earth is subject to periods of cooling and warming. During the warming phase, gases trapped solar energy and kept the planet's surface warm. These gases are described as greenhouse gases. The warming phase reaches a point where arctic ice melted and flooded large areas of land. Since the earth is a system that would seek equilibrium, extreme cooling will follow by extreme warming. The dinosaurs that survived the flooding faced the Ice Age. No dinosaur could withstand this one-two punch of the environment.

Stress theory - According to Heinrch K. Erben, a dedicated digger of dinosaur eggs, the environmental changes placed too much stress on the physiology of dinosaurs. Millions of years before the ill-fated end of the Cretaceous period (when dinosaurs ended their reign over Earth), the dinosaur eggs have thick shells. Towards the Cretaceous period, the eggshells are thinner, decreasing the chances of survival of baby dinosaurs. Erben suggested that the predatory dinosaurs won't have enough food and died of starvation.

Brain function theory -Dinosaurs had the reputation of having small brains. Their undersized brains and their oversized bodies put them at a disadvantage. If the Darwinian theory of survival is followed, these dinosaurs are expected to become extinct, eventually. The brains of these dinosaurs are not capable of adapting to the changes that the planet is undergoing.

Volcanic activity theory - During the Cretaceous period, there was a lot of volcanic activity. The prehistoric volcanoes spew out ash and hydrochloric acid. The great quantities of ash prevented sunlight to come through and could have traumatized the dinosaurs. But the high concentrations of hydrochloric acid did the dinosaurs in. The acid destroyed the ozone layer, which allowed dangerous solar radiation to hit the beleaguered bodies of the dinosaurs. Since then, of course, the ozone layer has recovered.

Which of the above theories is the most plausible? Most scientists adhere to the asteroid impact theory. But the greenhouse effect theory is just as convincing. Why do we, Homo sapiens, debate over these theories? Why do we want to know how dinosaurs became extinct? The reason is fear. Sixty-five million years ago, the dinosaurs were the dominant species but they were wiped out. Today, humans are the dominant species. We want to prevent our own extinction.

Learn more about this author, Mayflor Markusic.
Click here to send this author comments or questions.