Early Oxygen

[tirant]

Earth had enough oxygen for complex life 400 million years earlier than previously thought. One impact of this would be to further discredit the Cambrian "explosion" as being the rise of complex animal life.

Now if only there was someone in our membership who could talk about ancient oxygen levels as assessed through sulfur deposits...

Comments

[geomusicon]

Nobody thinks that Cambrian "explosion" (better termed the Cambrian Radiation) was the rise of complex life.

This occurred about 100 million years earlier with the rise of the Doushantuo and Ediacaran biotas...and sponges before then.

[geomusicon]

I'll read the Nature paper, but for now, the photo they show looks like the pyrite in question is diagenetic (formed much later).

[tirant]

I thought that for a while at least, the Cambrian was viewed as the start of complex life, complex here meaning "big animals" (and from our viewpoint, wacky).

[geomusicon]

That's understandable, but we now know that the first macroscopic complex life shows up in the fossil record during the newly named (2006) Ediacaran Period. The Cambrian Radiation is still significant, however, the idea that it came about because of oxygen is old and untested. In other words, nobody has demonstrated that there was a rise in oxygen coincident with the Cambrian Radiation. On the other hand, there is an exciting new hypothesis that suggests that the huge increase in diversity during the Cambrian was due to the fact that animals had fewer micro RNAs which we know limit gene expression. IN other words, life was able to "experiment" more widely with different body shapes than it can today.