Delay in Evolution May Be Down to Toxic Level of Sea; New Research Looks into Effect of Chemical 'Layering'

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Byline: Nicola Juncar

TOXIC seas may have been responsible for delaying the evolution of life on Earth by one billion years, according to new research from experts at Newcastle University.

The study reveals for the first time a chemical "layering" of the ocean which may have delayed the evolution of our earliest animal ancestors.

Using novel geochemical techniques developed by Newcastle University's Dr Simon Poulton, the team found that underneath oxygenated surface waters, the mid-depth oceanic waters were rich in sulphide about 1.8 billion years ago and these conditions may have persisted until oxygenation of the deep ocean more than one billion years later.

These widespread sulphide conditions close to the continents, coupled with deeper waters that remained oxygen-free and iron-rich, would have placed major restrictions on both the timing and pace of biological evolution.

Dr Poulton, who led the research, explained: "It has traditionally been assumed the first rise in atmospheric oxygen eventually led to oxygenation of the deep ocean around 1.8 billion years ago.

"This assumption has been called into question over recent years, and here we show that the ocean remained oxygen-free but became rich in toxic hydrogen-sulphide over an area that extended more than 100km from the continents. …