Cheers to the scientific process!
Turns out we might be very wrong about how life arose on Earth.
For decades now, the prevailing scientific theory explaining the Precambrian Avalon explosion — in short, the era dating back to about 685 to 800 million years ago in which multicellular organisms began to proliferate in Earth's oceans — has, put simply, been that an influx of oxygen into Earth's oceans accelerated the evolution of more complex life, ultimately paving the way for our planet's biosphere as we know it.
But as an international team of scientists suggests in a recently-published study, ancient rock samples show that this widely-accepted theory likely isn't true — meaning that we might just need to rewrite students' science textbooks.
"The fact that we now know, with a high degree of certainty, that oxygen didn't control the development of life on Earth provides us with an entirely new story about how life arose and what factors controlled this success," said Christian Bjerrum, an associate professor of geosciences and natural resource management at the University of Copenhagen and a co-author of the study published in the journal GeoBiology, in a statement.
"Specifically," he added, "it means that we need to rethink a lot of the things that we believed to be true from our childhood learning. And textbooks need to be revised and rewritten."
Less Is More
Per the study, the scientists meticulously mapped the geochemical makeup of ancient rock samples from the Omani mountain range in the Arabian peninsula. By examining the compositions of the samples, they determined that there likely wasn't any major flood of oxygenation after all — and actually, there was probably less oxygen in Earth's oceans at the time of the explosion than in years prior.
"Our measurements provide a good picture of what average oxygen concentrations were in the world's oceans at the time," said Bjerrum. "And it's apparent to us that there was no major increase in the amount of oxygen when more advanced fauna began to evolve and dominate Earth."
"In fact," he added, "there was somewhat of a slight decrease."
That said, the researchers still think that oxygen levels still played a central role in the proliferation of ancient multicellular species — and interestingly enough, they say that the decrease in oceanic oxygen may have ultimately been the culprit.
"It's interesting that the explosion of multicellular organisms occurs at a time with low concentrations of atmospheric and oceanic oxygen," said Bjerrum. "That indicates that organisms benefited from lower levels of oxygen and were able to develop in peace, as the water chemistry protected their stem cells naturally."
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