251 million years ago, at the end of the Permian period, over 90% of the species on Earth became extinct. The most widely accepted explanation for this event is that it was triggered by a series of volcanic eruptions over vast areas of Siberia, which caused a dramatic rise in greenhouse gas emissions.
However, Daniel Rothman, of the Massachusetts Institute of Technology, has analysed a sample of end-Permian sediment from China and concluded that carbon levels increased too quickly for geological processes to have been responsible. However, microbes can generate carbon compounds quickly enough. Rothman's group analysed the genome of Methanosarcina, a methanogenic archaeon responsible for most of the Earth's biogenic methane today, and found that it acquired the ability to generate methane at around the time of the end-Permian extinction. Moreover, Methanosarcina requires large amounts of nickel to produce methane quickly, and further analysis of the Chinese sediment revealed that nickel levels in it reached a peak value almost exactly 251 million years ago, probably because the Siberian lavas were rich in the metal. Rothman believes that these various strands of evidence indicate that Methanosarcina triggered the end-Permian extinction.
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Bill Gray.