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The demise of the dinosaurs is well-documented. Less well-known is the fate of some of the Earth's earliest life-forms - methane-producing microbes - yet if they had not died down, complex life as we know it may not have evolved, according to a researcher at The University of Western Australia.

Winthrop Professor in the School of Earth and Environment, Professor Mark Barley, is the co-author of a paper, "Oceanic nickel depletion and a methanogen famine before the Great Oxidation Event" to be published in Nature today (Thursday).

Because they produced methane, a gas which reacts with oxygen, these early microbes prevented the Earth's early atmosphere from being oxygenated, Professor Barley said. Only when the planet began to cool - resulting in a reduction of nickel in the oceans - were oxygen producing photosynthetic bacteria able to thrive.

"The nickel crash after its early boom 2.7 billion years ago helped make our planet habitable by complex life," he said. "Methane-producing microbes (methanogens) require the element nickel for their life and for the formation of methane. "Prior to 2.7 billion years ago the global oceans were very nickel-rich and would have supported a huge methanogen population resulting in a methane-rich atmosphere. When oceanic nickel contents declined after this time this would have caused a famine for methanogens and significantly reduced the methane content of the atmosphere."

Along with the study's lead researcher Kurt Konhauser and his team of geobiologists from the University of Alberta, Professor Barley studied the nickel content of banded iron formations (our main source of iron ore) - rocks which preserve a history of the state of the oceans over millennia.

By modeling the nickel content of the ancient oceans, they posited that the cooling of the Earth's interior and reduction of oceanic nickel content caused a major drop in methane production. This may have helped photosynthetic bacteria to evolve and/or helped them become a dominant microbial population necessary for the oxidation of the atmosphere.

Professor Barley decided to become a geologist 40 years ago when living at Kambalda during a more recent nickel boom - that of the 1960s.

Media references

Professor Mark Barley (+61 8) 6488 7322  (+61 4) 19 942 108
UWA School of Earth and Environment)
Janine MacDonald (UWA Public Affairs)  (+61 8) 6488 5563  (+61 4) 32 637 716