UK Daily Mail 
April 2, 2010
An hour-long hailstorm from space bombarded the Earth 13,000 years ago – plunging the planet into a mini-ice age, scientists claimed today.
The catastrophe was caused by a disintegrating comet and saw the planet sprayed by thousands of frozen boulders made of ice and dust.
The collisions wiped out huge numbers of animal species all over the world, disrupted the lives of our stone age ancestors and triggered a freeze that lasted more than 1,000 years.
The theory is the brainchild of Professor Bill Napier, from Cardiff University, who says it explains the mysterious period of extinction around 11,000 BC.
Scientists have long been puzzled by what caused a sudden cooling of up to 8C (14F) just as the Earth was warming up at the end of the last ice age.