Labrador is where life began, study suggests

For the second time this year, a geological discovery from the very earliest era of the Earth’s history suggests that northeastern Canada, between Hudson Bay and the Torngat Mountains of Labrador’s Atlantic coast, is the burial site of the oldest life on the planet.

This subarctic region, where the Earth’s oldest continental crust, the North Atlantic Craton, is exposed at the surface, has been a prime target for research about the origins of life, both on this planet and others.

Unlike most of the Earth’s modern crust, some of the Craton’s features date back to the Hadean era, more than four billion years ago.

It is so named for the boiling hellscape the planet would have been as it cooled, still hot from its creation half a billion years earlier out of the collision of many smaller planets and asteroids.

It was in that environment, as the oceans cooled and grew, that life first started to leave behind evidence of its presence.

This spring, after field work on the Nuvvuagittuq Greenstone Belt on Hudson Bay near Inukjuak, Que., British researchers reported the discovery of tiny tubeshaped, thread-like fossilized remains of primitive bacteria that seemed to have formed around hydrothermal seafloor vents. The rocks that contained them were dated to at least 3.77 billion years ago, far older than the oldest undisputed evidence of life, at around 3.5 billion years ago.

But there was scientific disagreement both over what they were, and how old they really were.

Now, after a detailed geological analysis of microscopic grains of graphite taken from the Labrador coast, south of the Torngat Mountains near the remote Shuldham Island on what is known as the Handy Fault Line, a team of Japanese researchers concluded they were created by the digestion of Earth’s earliest life forms, dated to 3.95 billion years ago.

This graphite, they claim, was created by autotrophs, literally “self-feeders,” which are organisms that use chemical or solar energy to create complex, energy-rich organic compounds from other, more basic substances in its environment.

Plants are autotrophs, using sunlight for photosynthesis of organic compounds. Humans and other animals are heterotrophs, meaning they rely on autotrophs and the food chain for energy.

The researchers found the tiny grains of graphite in what is known as the Uivak Gneiss, along the boundaries of other minerals, often in elongated shapes, or sometimes enclosed in crystals of quartz or garnet.

The discovery, which if confirmed would set back the earliest known life on Earth by many millions of years, comes as the search for life on other planets is making a strategic shift, returning to first principles as it reconsiders its historical biases about what life is, where it might originate, and what evidence it might produce.

The problem is, scientists have mainly looked for other versions of themselves, and failed to imagine how they might discover life on a planet that looks today like the Earth looked four billion years ago, teeming with unintelligent microscopic life that has not yet evolved into higher forms.

“The discovery of the biogenic graphite (in Labrador) enables geochemical study of the biogenic materials themselves, and will provide insight into early life not only on Earth but also on other planets,” the researchers from the University of Tokyo reported Wednesday in the journal Nature.