Thursday, September 10, 2009

Looking in the Wrong Place?

Research out of the University of Copenhagen suggests that we have been looking in the wrong place for a source of oxygen that had to have been present for life to evolve on earth at the end of the Proterozoic eon. The story, in ThaiIndian states:

By analysing the isotopes of chromium in iron-rich sediments formed in the ancient oceans, a scientific team, led by Professor Robert Frei at the University of Copenhagen in Denmark, has found that a rise in atmospheric oxygen levels 580 million years ago was closely followed by the evolution of animal life.

The data offers new insight into how animal life - and ultimately humans - first came to roam the planet.

“Because animals evolved in the sea, most previous research has focussed on oceanic oxygen levels,” explained Newcastle University’s Dr Simon Poulton, one of the authors of the research paper.

“Our research confirms for the first time that a rise in atmospheric oxygen was the driving force for oxygenation of the oceans 580 million years ago, and that this was the catalyst for the evolution of large complex animals,” he added.

Distinctive chromium isotope signals occur when continental rocks are altered and weathered as a result of oxygen levels rising in the atmosphere.

According to the research, oxygen levels began to rise around 2.8 Gya but dropped again and did not experience its second rise until around 580 Mya. This would put it after the the most recent (Kaigas) of the "snowball earth" periods (assuming that is a viable theory).

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