Poop Theory of Cambrian Explosion

[mith]

http://www.environmentalgraffiti.com/?p=566

Yes, someone postulated a feces based explanation for oxygen increase.

[AstusAleator]

Sounds reasonable...ish

[MichaelXY]

That explains why people are full of poop

[Darby]

The oxygen levels rose long before the Cambrian Explosion.

If they had risen just before, that would always be a factor in the explanations.

Also, the C12 - C13 ratios don't change up a food chain enough to show up in modern ecosystems, let alone fossils. Fossils that old have lost all of their radioactive carbon, anyway - that's why carbon dating only goes back tens of thousands of years, not hundreds of millions.

[MichaelXY]

It is true that the element Carbon is only good for about 10k years, but there are other elements such as U-238 that can be dated to 4 billion years.

[Darby]

Absolutely, but those isotopes couldn't be used to puzzle out the carbon ratios in the fossilized material (in fact, those isotopes originated outside the original organisms).

[mith]

How much earlier?

"He points out that feces producing creatures, ones that ate food then excreted it like humans today, first arrived around 40 million years before the Cambrian period. He argued that their poo was what allowed oxygen levels to rise, and evolution to explode."

[blcr11]

These guys measured C-12/C-13 ratios, which is not the same thing as radio-carbon dating. C-12 and C-13 atoms are stable, non-radioactive isotopes. They don’t go away over time like a radioactive element does, although one of the possible of C-14 decay products can be C-13. C-14, produced in the upper atmosphere by cosmic-ray bombardment of N2 for the most part, is radioactive with a half-life of about 6 thousand years and can be used to date biological ojects as old as 30-40,000 years of age. In this report, all they really were trying to do was document a possible enviromental event in rocks whose dates have to be established by other means—either another isotopic method, or by geologic context. It is kind of a cute idea. Of course, their explanation for the isotopic ratio shift may or may not be correct, never mind whether the isotopes are stable or not. About all you can say for it is that "it fits the timetable."