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31 May 2013
Climate change - prehistoric style

In an extract from 'The Origin of the Species', Charles Darwin wrote that "Climate plays an important part in determining the average numbers of a species, and periodical seasons of extreme cold or drought seem to be the most effective of all checks". This theory has been dramatically proven by recent investigations into the cause of the extinction of the majority of major animals in North American, Europe and the Middle east 12,800 years ago.
     It has long been known that a major climatic event occurred at that time but the cause of the event was open to speculation. Now a team from University College of Santa Barbara (USA), headed by emeritus professor in earth sciences, James Kennett, believes it may have found the answer.
     They have been examining very small round objects, known as spherules, from dozens sites spreading across North America, Europe and the Middle east. Several theories had been previously proposed over the formation of these spherules, from volcanic activity, through lightning strikes to widespread fires. But the detailed analysis carried out by the team showed that their formation required temperatures in excess of 2,200 degrees Celsius. Therefore the only theory remaining was that of a massive cosmic shower.
     The impact of this shower would have had the effect of blocking out the sun and causing a dramatic and extreme drop in temperature across the area obscured. This would explain the rapid decline in large mammal numbers and also the disappearance of the Clovis culture, which depended on hunting these animals for survival.
     In citing the paper, which was the culmination of this research, James Kennett is quoted as saying "Based on geochemical measurements and morphological observations, this paper offers compelling evidence to reject alternate hypotheses that YDB (Younger Dryas Boundary) spherules (were) formed by volcanic or human activity; from ongoing natural accumulation of space dust; lightning strikes; or by slow geochemical accumulation in sediments. This evidence continues to point to a major cosmic impact as the primary cause for the tragic loss of nearly all of the remarkable American large animals that had survived the stresses of many ice age periods only to be knocked out quite recently by this catastrophic event".

Edited from EurekaAlert! (21 May 2013)

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