Cambrian Explosion: role of oxygen (Introduction)

by David Turell , Wednesday, February 19, 2014, 15:46 (3712 days ago) @ dhw


> Dhw: Many apologies if I am being dense here, but surely the test is not whether the earliest animals could live with 0.5%, but whether LATER animals can. If they can't, then clearly later animals could only evolve when the level of oxygen increased. Perhaps, David, you could explain how tests on earlier animals prove that later animals could have existed on the same amount of oxygen but didn't.-Note my previous comment: " But of course, these low use of oxygen animals could have started with a high use metabolism and then lowered it. This finding on current animals now really can't be related to the past, or can it? I have my doubts.
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> QUOTE: "His colleagues from the Nordic Center for Earth Evolution have previously shown that oxygen levels have actually risen dramatically at least one time before complex life evolved. Although plenty of oxygen thus became available it did not lead to the development of complex life."
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> dhw:We would need to know more details. How dramatically? Dramatically enough to support modern animals? How accurate can any of these measurements be? But in any case, the fact that conditions are suitable for innovations does not mean that innovations will take place. (The same applies to life itself.) That depends on the nature of the organisms that are around, and how they interact with those conditions.-It seems to be fairly accepted that oxygen levels rose dramatically just before the Cambrian. I can't quote the methods of research to you. but you are perfectly right: ideal conditions allow for complex advances, but that doesn't mean those advances are required to occur.