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Maverick theory: Cambrian animals remade the environment by generating oxygen


From Jordana Cepelewicz at Quanta:

For decades, researchers have commonly assumed that higher oxygen levels led to the sudden diversification of animal life 540 million years ago. But one iconoclast argues the opposite: that new animal behaviors raised oxygen levels and remade the environment.

n a paper published in the January issue of Geobiology, Butterfield braided fluid dynamics and ecology to present his case for animals driving oxygenation instead of the other way around. First, he argued, if there was enough oxygen to power unicellular eukaryotes 1.6 billion years ago — which was indeed the case — then there would have been enough to run a whole assortment of animals. He believes early multicellular organisms would have consisted of flagellated cells moving in unison, collectively whipping their appendages to create currents that would have made it easier for them to obtain dissolved oxygen. “I make the case that if there’s enough oxygen to run a single-celled eukaryote, there’s enough oxygen to run a fish,” Butterfield said. “So oxygen limitation cannot be invoked to explain the billion-year delay in the evolution of animals.”

Instead, his hypothesis focuses on diurnal vertical migration, a daily process during which sundry organisms, ranging in size and complexity from zooplankton and sponges to fish and squids, migrate between shallow and deeper waters to find food and avoid predators. By feeding up above and metabolizing down below, the animals scrub and help ventilate the ocean, raising oxygen concentrations at the surface while driving anoxic regions to greater depths. More.

The trouble with maverick theories today is that they usually aren’t really mavericks. They are merely theories that stretch reality past the shredding point. Note the use of “would have.”

But yes, interesting, anyway.

The Cambrian would make great theatre if it weren’t just all about animals.

See also: Secrets of 520 million-year-old brain debated, raise conundrums

The "maverick theory" described in the title isn't the one described in the Quanta piece. In that, animals don't generate oxygen, they re-distribute it in the water column. Bob O'H
Overthinking. Much simpler theory: Microbes on the plantish side became better at photosynthesis and dominated the ocean surface.
I also prefer the simpler solutions. But I wouldn't underestimate the impact of the behaviour of "animals" (heterotrophs) on oxygen liberation. I don't know if anyone has looked at grazing rate on oxygen liberation in natural plankton communities. It seems counterintuitive that grazing would actually increase phytoplankton production, but this is the case. It seems to reason that grazing, within limits, would also increase oxygen liberation. Allan Keith
Overthinking. Much simpler theory: Microbes on the plantish side became better at photosynthesis and dominated the ocean surface. (As they still do today.) polistra

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