The researchers who claimed to have found the oldest traces of life five years ago are now even more confident.

‘World’s oldest fossils discovered in Canada,’ headlined Scientias five years ago. Geochemist and astrobiologist Dominic Papineau and colleagues then claimed to see traces of microbes in a rock dating from 3.75 to 4.28 billion years ago. That life would then possibly have arisen only a few hundred million years after the formation of the earth.

At the time, this led to a lot of criticism among colleagues† Now team-Papineau comes with a new scientific article, based on closer examination of the same stone. Know that to convince the critics?

speculative ideas

In 2017, Papineau and his team already made notification of tubes and wires in the fist-sized stone, found in the north of the Canadian province of Quebec. The wisps they saw, made from the ferrous mineral hematite, were unlikely to have formed from changes in pressure and temperature in the rock, the researchers said. Instead, they would have been created by bacteria oxidizing iron to get energy.

Papineau himself spoke of “direct evidence of one of the oldest life forms on Earth”, but others were far from convinced. Geologist Wouter Bleeker for example, from the Canadian Geological Survey said in The New York Timesthat the researchers “built on speculative ideas and seemed completely oblivious to the substantial evidence against their interpretation.”

Tree-like structure

We are now five years later – and it appears that Papineau has not been idle. In a voluminous article in the scientific journal Science Advances he now mentions a much larger and more complex structure in the same stone. This structure measures about one centimeter and has a “tree-like” shape, with the branches running parallel to each other. There are bubbles around it. According to the researchers, there are no known chemical processes that can produce such a structure.

Another key point the researchers make, says Arnold Driessen, professor of molecular microbiology at the University of Groningen, is that the structure was ‘trapped’ in fine quartz. “That is a very stable rock that is less sensitive to shifts in geological layers. That makes it more unlikely that these structures later found their way into the bedrock.”

A resounding ‘no!’

However, geologist Bleeker is still very critical. As far as he is concerned, it is by no means certain that the stone is indeed at least 3.75 billion years old, and perhaps even 4.38 billion years old. “There is zero hard evidence for that.”

Furthermore, according to Bleeker, the rock has been exposed to temperatures above 600 degrees Celsius — probably more than once. “Can an ancient, microfossil-like structure survive? Most people who know anything about how rocks deform would answer the question with a resounding “no!” reply.”

Bleeker therefore thinks that the structures Papineau writes about only arose about 2.7 billion years ago. This would make them much more recent than the oldest known terrestrial life.

Billions of years old prints

Regardless of how old the structures Papineau has found are: were they indeed made by life? “That is possible, but very difficult to prove,” says Bleeker.

Driessen agrees. “It’s a really big challenge to establish that.” Ultimately, you don’t look at the material that any organisms themselves were made of, he explains, but at prints from billions of years ago. “And based on that, you will never get your evidence watertight. You will always be controversial.”

But if the claim of Papineau and colleagues turns out to be correct, then according to Driessen it would be a groundbreaking discovery. “Then life on Earth would have arisen much earlier than we thought.”