Thursday, May 04, 2006

...lada da da da, feelin' lucky...

Mammalian species have a typical run of about 2 million years before they go extincty-poo. We are mammals. The oldest homo sapien fossils found so far are about 1.4 million years old. The only other homo sapien subspecies, homo sapiens idaltu, is already extinct. Our nearest living relatives are chimpanzees and bonobos. Our mutual evolutionary branches separated somewhere around 6.5 million years ago.

Hmmm. Do you feel lucky, punk? Well, do ya?

Geologists and paleobiologists divide the history of the planet into blocks of time, which are associated with a uniquely characteristic fossil record left behind in the rock. At the dividing points between these eras, periods, epochs and ages are usually very distinct discontinuities in the record. Something major happens which radically alters what is seen in the strata. Radical change is common, in our planets history.

Still feeling lucky?

Science has divided deep time into 4 eras (the Precambrian, Paleozoic, Mesozoic, Cenozoic). The differentiations between them are major – as in, major extinction events. Nearly all dominant species of the previous era go bye bye and new stuff emerges.

The major extinction event most are familiar with is the total kill off of the dinosaurs, leading to the beginning of the current age of mammals. That marks the end the Mesozoic and the beginning of the Cenozoic eras. The best candidate for what caused this is an Apollo Asteroid – a 6 mile in diameter asteroid which struck the earth, where the Yucatan Peninsula is today, creating the 100 mile wide Chicxulub Crater.

But what about that other, earlier, major extinction event (actually, the record points to two nearly concurrent major extinctions); the one between the Paleozoic and Mesozoic? The one that ended the age of fishes? It wiped out nearly half of the fish and invertebrate species, 75% of all amphibians, maybe as much as 96% of all marine species. They call it the Permian Extinction – what about it?

Well, no one knows for sure – but there are hints. Dramatic glacial pulsations occurred. There were major retreats in ocean size. There is evidence of a brief and intense greenhouse event. The dramatic increase in CO2 would have suppressed the upwelling of the oceans, eliminating nutrient growth at the lowest links in the food chain.Plate tectonics could have disrupted the oceans currents, also impacting nutrients.

Now, if you’re still feeling lucky, read this.

If you get to the 4th paragraph and still feel lucky, Clint Eastwood may have to shoot you.


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