Extinct I recently received a letter from a young reader from Oakville who asked the Conservation Department to bring back a now extinct species of parrot. We can't help him. Extinction is death. The probability of an extinct species resettling the earth is so small as to be non-calculable, no matter how many zeros we place after the decimal point. Is it any wonder that biologists treat extinction so seriously, and why they want to rescue animals and plants that are facing extinction.
Some extinction occurs naturally.
As new species evolve and weather patterns change some species drop away, unable to compete in the changed environment. Scientists have calculated what they call a background or normal rate of one extinction per major group every million years. Cataclysmic changes accelerate this rate of extinction. Life on earth has experienced at least five major mass extinctions that are believed to have been caused by terrific changes of climate brought about by upheavals of the earth's crust or by collisions with asteroids, comets or meteors. During those five major extinctions, anywhere from 60 to 95 percent of existing species disappeared within what has to be considered a snap of the finger in geological time.