A new link between nickel, methane gas and the evolution of complex life forms on Earth

Konhauser and his team have a new theory on what caused the decline of methane producing bacteria 2.7 billion years ago and the subsequent rise of oxygen levels. This new paper shows that as the planet's mantle cooled there was a sharp decrease in nickel-rich volcanism.

"Nickel was the nutrient that methogen bacteria used to produce methane gas," said Konhauser. "The methogens starved, and as methane gas levels fell, oxygen levels rose in the oceans and in the atmosphere."

Approximately 2.4 billion years the planet became oxygenated to a level that allowed the evolution of complex life forms.

Konhauser says that this paper is the first to link to changes in Earth's volcanism to the microbial populations that determined the timing for the rise of atmospheric oxygen.