“Oxygen flooded into the atmosphere as a pollutant, even a poison, until natural selection shaped living things to thrive on the stuff and, indeed, suffocate without it,” wrote evolutionary biologist, Richard Dawkins, in The Greatest Show on Earth: The Evidence for Evolution.
“Contrary to our first expectations, global climate was not the primary cause of this change in ocean oxygen and nitrogen cycling,” said biogeochemist Emma Kast currently at the University of Cambridge about the planet’s dramatic increase in oxygen 55 million years ago. The more likely culprit? Plate tectonics. The collision of India with Asia — dubbed “the collision that changed the world” by Columbia University geoscientist Wally Broecker, a pioneer in the ocean’s role in climate change.— closed off an ancient sea called the Tethys, disturbing the continental shelves and their connections with the open ocean.
“Our theory is the only one that accounts for the global impact on the production of oxygen over such a sustained period of time and explains why it was able to rise to the levels we see today, fueling the evolution of life on Earth,” says William Martin at Heinrich-Heine-Universität Düsseldorf.