We might have discovered the oldest animal fossils yet in the Canadian Northwest


Geologists in Canada might have found the earliest evidence of life on Earth: fossilized sea sponges.

Image after Elizabeth C. Turner, (2021), Nature.

In the remote mountains of the Northwest Territories — an area reportedly only accessible by helicopter — geologist Elizabeth Turner has found the oldest evidence of animal life that we’ve ever come across. Since the 1980s, she has been excavating this area, which used to be a marine environment around one billion years ago. But after all those years of hard work finally paid off, as Turner reports finding the fossils of ancient sponges preserved in the sediments here.

Even better, they could be the oldest animal fossils we’ve ever found.

Primeval sponges

The emphasis here is on ‘could be’. Thin sections of rocks recovered from the site contain three-dimensional shapes that are very similar to the structure of modern sponges. We’re not entirely sure that they are fossilized sea sponges right now.

What we do know, based on the dating of the rock layers the samples were retrieved from, is that they’re around 890 million years old. If we can confirm that these are actually fossils, they would be roughly 350 million years older than the oldest confirmed sponge fossils we’ve found so far.

Sponges, as one of the simplest types of animals out there, are widely considered to have been the first group of animals to evolve on Earth. If not the first, at least one of the first. Sponges lack nervous systems or muscles, and their cells work more like a collective of individuals rather than a single whole. That being said, however, they do have some definitory traits of simple animals, such as cells with differentiated functions and sperm.

Still, that being said, there are still a lot of unknowns when talking about early life on Earth. Our hypothesis so far is that life emerged around 3.7 billion years ago, with the first animals likely making an appearance around 540 million years ago — sponges. However, geneticists using the molecular clock approach — which involves analyzing the rate of genetic mutation in a species to estimate where it likely diverged from its cousins — say that there are grounds on which  to assume that sponges emerged much earlier, likely around one billion years ago.

No physical evidence has been found in support of this last point so far, but if the samples unearthed by Turner are confirmed as being sponge fossils, they would go a long way towards validating it. As such, we can definitely expect researchers to thoroughly examine and debate Turner’s findings.

The paper “Possible poriferan body fossils in early Neoproterozoic microbial reefs” has been published in the journal Nature.


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