The global extinction of megafauna –giant mammals such as mammoths, mastodons, saber-toothed tigers, and giant sloths has been one of the great mysteries of paleontology. The classical suspects have been global warming (the end of the Ice Age) and over-hunting by humans. These causes are suspect as complete explanations for a variety of reasons, such as evidence that humans have been hunting mammoths as early as 1.8 million years ago, and the mid-Pliocene global warming that failed to cause a mass extinction.
Newly uncovered evidence offers a radical new theory – meteorites. Magnetic metal particles have been discovered in mammoth tusks, with compositions and impact patterns that clearly indicate un-earthly origins. There are no recorded instances of a human being killed by a meteor, so the discovery of meteor particles in at least eight animals from different time periods suggests repeated, devastating strikes. The scientists also found a black layer in the sediment, which may be “the charcoal deposited by wildfires that swept the continent after the space object smashed into the Earth’s atmosphere.”
Most people believe that nature operates by slow, gradual changes, which drive the extinction and formation of species. Yet the new evidence supports the view that evolution substantially operates by regular cataclysmic events. Furthermore, nature is not only well-adapted to catastrophe, but relies on crises to weed out fragile species which are over-adapted for specific environments – for example, the fangs of the saber-toothed cat, or the dietary requirements of panda bears.
Update: besides meteorites, trees were recently identified as suspects in the extinction of woolly mammoths:
Professor Adrian Lister, a palaeobiologist at University College London, has found that the extensive areas of frozen grassland on which mammoths thrived were gradually replaced by forests, leaving the animals nothing to eat. Analysis on the DNA extracted from hundreds of fossils has revealed that the genetic differences between individual mammoths were so slight that the animals were unable to adapt to the changes in their environment.