VANCOUVER - A new study says oxygen first appeared in Earth's atmosphere up to 700 million years earlier than believed.

Scientists at the University of British Columbia and the University of Copenhagen looked at three-billion-year-old soil from South Africa — the oldest soils left in the world today.

The Earth was formed 4.6 billion years ago and, based on the chemical composition of the soil, the scientists believe the oxygen that sparked evolution appeared three billion years ago.

It was previously believed that oxygen began to accumulate in our atmosphere only about 2.3 billion years ago.

UBC assistant professor and co-author of the study Sean Crowe says this event forever changed the composition of Earth's atmosphere, and ultimately led to the evolution of animals and humans.

The paper was published today in the scientific journal Nature.

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