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BOB HIRSHON (host):
A mystery of the Earth’s history…I’m Bob Hirshon and this is Science Update.
Imagine the Earth about two and a half billion years ago. Bacteria that produce methane gas rule the oceans and there’s no oxygen in the atmosphere. But then, oxygen-producing bacteria start to flourish, and the oxygen allows new life forms to develop. Geomicrobiologist Kurt Konhauser and his colleagues at the University of Alberta tried to figure out what triggered this important change. They found that up until about 2.7 billion years ago, the amount of the trace metal nickel in seawater was very high.
KURT KONHAUSER (University of Alberta):
And by the time 2.5 billion years comes along, the concentration of nickel halves. So there’s a big drop in nickel between 2.7 and 2.5 billion years ago.
HIRSHON:
He says the drop in nickel allowed oxygen-producing bacteria to outcompete methane-producing bacteria, which required more nickel to survive. So I’m Bob Hirshon for AAAS, the science society.