Scientists Track Earth's Early Oxygen

TEMPE, Ariz., Oct. 11 (UPI) — U.S. scientists say they’re closer to discovering how and when Earth’s early oceans and atmosphere gained their oxygen, vital for life on the planet.

Utilizing a technique developed at Arizona State University to estimate oxygen levels in ancient oceans from the chemical composition of seafloor sediments, researchers say they’ve identified an increase in oxygen about 400 million years ago that brought it to levels comparable to today, a university release said.

The international study by scientists from Harvard, Denmark, Sweden and the United Kingdom says the timing matches the emergence of large predatory fish and higher orders of plants.

“There has been a lot of speculation over the years about whether or not oxygen in the atmosphere was steady or variable over the last 500 million years,” said Ariel Anbar, leader of ASU’s Astrobiology Program that developed the measuring technique.

“This is the era during which animals and land plants emerged and flourished. So it’s a profound question in understanding the history of life,” he said. “These new findings not only suggest that oxygen levels varied, but also that the variation had direct consequences for the evolution of complex life.”

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