03/20/02 - 14:23:59
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If we don't count over-hunting by aliens;), one current thought is that there are three ultimate causes of extinction that are well enough articulated to be testable with the fossil record. Ultimate causes, although usually not regarded as direct causes of extinction, lead to various proximate causes that result in extinction. The three ultimate causes are marine regression, volcanism, and asteroid impact. |
To keep it short, when combined with evidence from plants and marine species, it appears that all three ultimate causes, plus others we still do not know, each may have been necessary but clearly not sufficent to cause the extinctions.
Also, the speed at which species are being lost is much faster than it was in the past. Some predict that up to one-fifth of all living species could diasappear within 30 years.
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