Jun 25, 2008 6:02:07 PM cite

Years ago I read a comentary on the process (I think it took a thousand years or so) which led to Easter Island becoming uninhabitable. Very disturbing. There certainly can come a time when the last tree is cut and nothing is left to support us. (Did the island ever revive?) Will you please tell me of the past five "mass extinctions" you refer to?

by April

Jul 2, 2008 3:27:59 AM cite

Sure, April, thanks for asking. ........................... http://www.well.com/~davidu/extinction.html ............................................ The six i had in mind are:...................................... 440 Million Years Ago, in the Late Ordovician, 20 - 50 % Percent of Families Died Out; Tropical areas were hit hardest. No terrestrial vertebrates had evolved yet. .................................................. 360 Million Years Ago, in the Late Devonian, when 20 - 30 % Percent of Families Died Out; Many fish and marine invertebrates died out. Most fossil fuels like oil and coal were buried after this mass extinction. ................................................ 250 Million Years Ago, at the End of the Permian, 50 % Percent of Families Died Out. It was the greatest mass extinction ever (so far), possibly due to atmospheric dust from massive volcanic activity in what is now Siberia. .................................................. 213 Million Years Ago, in the Late Triassic, 20 - 35 % Percent of Families Died Out; Dinosaurs and mammals had just recently evolved; both live through this extinction. This is the time of the breakup of the supercontinent Pangaia. ............................................................ 66 Million Years Ago, in the Late Cretaceous, 15 % Percent of Families Died Out; Dinosaurs become extinct, probably caused by a meteorite colliding with the Earth in what is now the Yucatan peninsula. Mammals and fishes begin to proliferate in the ecological space opened by such death. 65 million of years after this mass extinction, early humans evolve. ................................... The current period is called the Holocene, already an Unknown Percent of Families have died out with more daily. Wide agreement that this pestilence of rapid extinctions is of anthropogenic causes, that is, resulting from the activity of human beings. ... But not all human beings; the ones who use money and participate in the global economy contribute to extinctions, whereas the few who live in traditional tribal ways are as sustainable as they have been for three million years now (although the wave of extinctions threatens them, too). ...................................................... Allow me to recommend an excellent book, THE SIXTH EXTINCTION by Richard Leakey, Anchor paperback ISBN-10: 0385468091. It gives a great overview of the other five, and one of the most readable, concise, and informed view on this current mass extinction.

by zotlynn

Jun 25, 2008 10:24:41 PM cite

Do an internet search on "Mass Extinctions" and you will find more than is practical to post on this site.

by thedoc