Biochemists have figured out how fluctuations in oxygen levels affected the evolution of animals

(ORDO NEWS) — The level of oxygen in the Earth’s atmosphere fluctuated greatly in ancient times, which created the conditions for the rapid evolution of animals, according to biochemists from the University of Leeds and the University of California.

Scientists believe that the level of oxygen in the Earth’s atmosphere has changed three times.

The first time – 2 billion years ago, when oxygen first appeared, the last time – 400 million years ago – the level of oxygen rose to the current level.

The second stage of changes, which began 1 billion years ago and lasted about 500 million years, according to scientists, played a key role in the early evolution of animals.

However, for a long time, scientists could not answer the question of whether the level of oxygen increased sharply or gradually.

To answer this question, the researchers studied the fossilized footprints of early animals, the Ediacaran biota. They have been found in sedimentary rocks ranging in age from 541 to 635 Ma.

Scientists used methods to measure carbon or carbon isotopes found in limestone rocks taken from shallow seas.

Based on the isotope ratios of the different types of carbon found, the researchers were able to calculate the levels of photosynthesis that existed millions of years ago and infer the level of oxygen in the atmosphere.

As a result of the calculations, they were able to obtain data on the level of oxygen in the atmosphere over the past 1.5 billion years.

“Our study shows that oxygen levels fluctuated constantly. Fluctuations between high and low oxygen levels have existed long before early life forms appeared.

This periodic change in environmental conditions could cause evolutionary pressure, in which some forms of life could die out or change, and new ones could arise, ”the scientists noted.

Thanks to such jumps in oxygen levels, evolution accelerated, they said, as some organisms died out, making room for more adapted ones.

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