We may finally know what life on Earth breathed before there was oxygen – Live Science

Billions of years ago, long before oxygen was readily available, the notorious poison arsenic could have been the compound that breathed new life into our planet.
In Chile’s Atacama Desert, in a place called Laguna La Brava, scientists have been studying a purple ribbon of photosynthetic microbes living in a hypersaline lake that’s permanently free of oxygen.
“I have been working with microbial mats for about 35 years or so,” says geoscientist Pieter Visscher from the University of Connecticut…

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