Dinosaurs died out around 65 million years ago and no one knows exactly why. The most popular theory is that a meteorite around 9 km across hit the Earth. If the birth rate is less than the death rate over time, extinction results.
Extinction is a natural result of evolution.
Changes in the earthly environment may have played a much bigger part in killing off the dinosaurs 65 million years ago than exotic visitors like asteroids, claims a new report. Instead, the Earth may have been bombarded by comets or asteroids for hundreds of thousands of years. The dinosaurs and other species would then have been wiped out in steps rather than all at once. More evidence that a huge meteorite hit Earth and helped to wipe out the dinosaurs has come from the precise age of tiny beads of glass in rocks in Haiti and volcanic rocks in Montana. Researchers from the US Geological Survey also established that the glass beads, called tektites, are the oldest known, more than twice the age of others dated.