The Saglek Block rocks of northern Labrador have been submerged beneath water, sucked into Earth’s interior, twisted, squeezed, and torn by tectonic forces, wrenched upward, weathered by wind and waves, and otherwise subjected to every imaginable form of battering a piece of stone can endure in the course of 3.95 billion years.
Yet a team of scientists believes that carbon atoms within those Canadian rocks provide persisting proof that tiny organisms once dwelled there.
If their analysis, published this week in the journal Nature, is correct, then the rocks contain some of the oldest signs of life on Earth. The discovery would push the origins of life even deeper into the planet’s history, to a hellish time when Earth was barely cooled and constantly colliding with other bodies in the solar system. It would mean that biology got started quickly and is even more resilient than we know.
Not all researchers are convinced, though.
This story might sound familiar. In the past 13 months, studies have come out about tiny 3.77 billion-year-old rock tubes and 3.7 billion-year-old microbial mats that also laid a disputed claim to the title “oldest evidence of life.” The full debate goes back decades, and scientists still don’t agree on what kind of evidence — and how much of it — is necessary to demonstrate that something is a fossil and not just a funny-looking stone.
The distinction is important, because this is about more than just earning a spot in records books, says NASA astrobiologist Abigail Allwood. One day, scientists may have the same debate over structures in a rock sample from another planet.
“For a discovery of such an extraordinary kind, you’d have to be 10 times as rigorous as you’d be on Earth,” Allwood said. “If we’re going to take the lessons learned and…