Changes

'''Extinction''' is when a [[species]] dies out completely.  It could be argued that it can occur before that, say, if there are only [[male]]s or [[female]]s left in a sexually reproducing species, or if the remaining pairs are geographically isolated preventing [[mating]].

'''Extinction''' is when a [[species]] dies out completely.  It could be argued that it can occur before that, say, if there are only [[male]]s or [[female]]s left in a sexually reproducing species, or if the remaining pairs are geographically isolated preventing [[mating]].

Over the [[history]] of the earth, many more species have become extinct than have existed at any one time.  Sometimes a species is replced by [[descendant]]s that have altered their form enough not to be considered the same species anymore.  An example of this is the history of the modern horse, which has descended through a series of distinct, and now extinct, [[precursor]] species.

[[Evolutionist]]s believe that over the [[history]] of the earth, many more species have become extinct than have existed at any one time.  Sometimes a species is replaced by [[descendant]]s that have altered their form enough not to be considered the same species anymore.  An example of this is the history of the modern horse, which has descended through a series of distinct, and now extinct, [[precursor]] species.