Life on Earth Is Older Than Initially Presumed

Researchers from the University of Washington found proof according to which life may have existed around 3.2 billion years ago instead of 2 billion years ago, as previously believed. The new findings were published in Nature.

Apparently life can exist without oxygen, but not without nitrogen. So researchers at the University of Washington took a look at some of the planet’s oldest rocks only to find evidence that life was already pulling nitrogen out of the air and converting it into a life supporting matter 3.2 billion years ago.

“People always had the idea that the really ancient biosphere was just tenuously clinging on to this inhospitable planet, and it wasn’t until the emergence of nitrogen fixation that suddenly the biosphere become large and robust and diverse. (…) Our work shows that there was no nitrogen crisis on the early Earth, and therefore it could have supported a fairly large and diverse biosphere,”

said co-author of the study, Roger Buick, an UW professor of sciences.

Researchers looked at 52 samples, 2.75 to 3.2 billion years old, which had been collected in South Africa and northwestern Australia. They are by excellence among the oldest rocks on our planet.

These rocks had been formed out of sediments deposited on continental margins,which means they are free of chemical irregularities that would normally occur near a subsea volcano. Moreover these rocks  formed before the atmosphere gained oxygen, phenomenon that took place about 2.3 to 2.4 billion years ago; this means that they preserve some chemical clues and facts that modern rocks no longer have.

These rocks’ fixing nitrogen basically means their breaking a tenacious triple bond that’c capable of holding nitrogen atoms in pairs in the atmosphere and of joining a single nitrogen to a molecule, which is easier for the living things to use.

According to the chemical signature of these ancient rocks, nitrogen was being broken by one of the most common of the three types of nitrogen-fixing enzymes that exist nowadays. In other words this means that early life is likely to have existed in single-celled layers on land, and exhaling small amounts of oxygen from down there. The oxygen therefore reacted with the rock and released molybdenum into the water.