Past Earth Extinctions Viewed As "Reset Buttons" For New Life Forms

By James Donahue

Scientists who study such things believe that throughout the history of this planet, catastrophic events occurred that brought about five different mass extinctions of living creatures.

Each time it happened, they say, life bounced back and the way was paved for new life forms to become the dominant species. They liken it to a "reset button" for living history.

The earliest of the "Big Five" extinction periods happened about 444 million years ago, and was a pretty explosive event. Researchers believe whatever happened brought on a pair of "die-offs" that involved massive glaciation and a drop in sea levels. They are kicking around a theory that giant and rich plant life pulled so much carbon dioxide out of the atmosphere that it caused a global cooling, created an ice age and killed most if not all life forms.

The second killing also happened in two parts, spaced between 100,000 and 300,000 years apart, sometime between 408 to 360 million years ago. Those are pretty big numbers and a lot can happen during time periods of such length, yet scientists want to link these events together into a single frame they call the "late Devonian extinction." They say there were two separate "pulses" involving severe drops in temperature, with heated steaming seas teaming with life suddenly dropping 78 degrees Fahrenheit. The sea creatures could not survive the cold.

At that time, only simple life forms living in the seas, and some plants were beginning to spring up on the land, as were some small insects. They all got wiped out again during the second big extinction, which was believed to have been caused by major volcanism. Another 10 million years passed before there were footprints from vertebrates on land again, the researchers say. That is how long it takes for life to spring from the pre-biotic chemistry that exists deep in the oceans, and slowly evolve.

It had a good start by the time the next mass extinction occurred roughly 250 million years ago. Scientists say this was probably the worst of all of the events that caused the mass killing of life on this planet. Some researchers estimate that most, probably 95 percent of the planet's species, died. Prophet Aaron C. Donahue sees a total die-off at that time, including an intelligent life form that was quite different from human. There is a genetic memory of a reptilian life form that preceded us. This extinction is believed to have been the result of massive volcanism in what is now Siberia.

The fourth great extinction was said to have happened about 200 million years ago. The primary form of life existing then were therapsids, or a reptilian type of animal that looked somewhat like the dinosaurs that came later, although there apparently was no genetic link. Researchers say this die-off paved the way for the rise of the dinosaurs as the main life forms on the planet.

The last or fifth extinction is the one we are most familiar with. It involved a cataclysm that killed the dinosaurs and roughly half of all species on the planet about 65 million years ago. The cause of this event is still under debate, ranging from volcanism to a collision with a large object from space.

Some believe that an early primate that became humanoid existed and may have survived this extinction period.

Of special interest is a vision by Donahue of yet an even earlier intelligent species that once existed on Earth, possibly before the first extinction. He said this was a very successful species that not only developed technology but even traveled into space.