LAWRENCE, KANSAS — Scientists have found evidence that a huge event may have caused a climate shift that affected the evolution of life on Earth.<br /><br />Newsweek reports that according to a new two-part study published in the Journal of Geology, fragments of a large, disintegrating comet struck Earth and triggered a massive firestorm some 12,800 years ago.<br /><br />The fires produced thick clouds of smoke and dust that covered the sky and cut off sunlight, causing the climate to cool rapidly and triggering a mini ice age.<br /><br />The cold climate lasted for a thousand years, killing off plants and many large animal species, and causing human populations to decline.<br /><br />Researchers came up with the impact theory after examining samples from 170 sites around the world, with chemical signatures indicating that 10% of the land surface was on fire.<br /><br />Analysis of pollen levels also suggests that pine forests had burned off and been replaced by poplar trees, a species that grows in barren ground.<br /><br />The theory is theorized to be the trigger event for the Younger Dryas period, a climate anomaly which saw gradual warming suddenly reverse.
