Researchers defend their theory that molecular oxygen existed on Earth 2.5 billion years ago

Living stromatolites at Shark Bay, Western Australia. Oxygen produced by ancient stromatolites may have left its mark on Earth’s environment as early as 2.5 billion years ago. Credit: Ariel Anbar

When did molecular oxygen, the gas that all large and complex forms of life on Earth today require to function, first appear on Earth?

For more than 15 years, work by a team of scientists led by Ariel…