Scottish rocks record ancient oxygen clues
Oxygen levels on Earth reached a critical threshold to enable the evolution of complex life much earlier than thought, say scientists.
The evidence is found in 1.2-billion-year-old rocks from Scotland.
These rocks retain signatures of bacterial activity known to occur when there is copious atmospheric oxygen.
The microbes' behaviour is seen 400 million years further back in time than any previous discovery, the researchers tell the journal Nature.
The team is not saying complex life existed 1.2 billion years ago, merely that the conditions would have been right for it to start to take hold.
"We're recording a key stage in the evolution of life on Earth," said Professor John Parnell from the University of Aberdeen.
"The evidence relates to a particular group of microbes that have been very successful through Earth's history and are now found everywhere from glaciers to the deep ocean floor....
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The evidence is found in 1.2-billion-year-old rocks from Scotland.
These rocks retain signatures of bacterial activity known to occur when there is copious atmospheric oxygen.
The microbes' behaviour is seen 400 million years further back in time than any previous discovery, the researchers tell the journal Nature.
The team is not saying complex life existed 1.2 billion years ago, merely that the conditions would have been right for it to start to take hold.
"We're recording a key stage in the evolution of life on Earth," said Professor John Parnell from the University of Aberdeen.
"The evidence relates to a particular group of microbes that have been very successful through Earth's history and are now found everywhere from glaciers to the deep ocean floor....