I noticed this story last week but ran out of time to write about it. A geologist believes she may have discovered fossil evidence of the first animal life on earth. Elizabeth Turner actually uncovered the fossils in the 1990s when she was still in school. She thought they could be significantly but only recently became convinced they were fossilized proof of sponges that existed nearly a billion years ago.

She collected the purported fossils from ancient microbial reefs preserved in the rocks of Canada’s remote Northwest Territories, starting during her graduate studies in the 1990s.

When Turner examined slices of the rock under a microscope, she saw branching networks of crystalline tubes. She later realized that these structures resemble the internal scaffolding of modern horny sponges, and line up with the expected decay and fossilization patterns of spongin, a collagen protein that forms their scaffolding.

It wasn’t until the past few years, when she saw studies that described similar structures in much younger rocks — from a time when sponges were known to exist — that Turner felt confident in publishing her results.

The image above shows the fossilized filaments she believes are from sponges. Turner has some supporters who think she’s onto something but also plenty of skeptics who think her evidence is less than convincing. Other scientists who’ve provided evidence of fossilized sponges in the past have sectioned the rocks and then create a 3D model of the fossilized collagen. Turner doesn’t have that sort of proof. Also, because she’s claiming to have found something that would move the earliest animal life backwards by several hundred million years it’s a big and important claim.

The dating of adjacent rock layers indicates the samples are about 890 million years old, which would make them about 350 million years older than the oldest undisputed sponge fossils previously found…

Until now, the oldest undisputed fossil sponges date to around 540 million years ago, an era called the Cambrian period.

But scientists using a line of reasoning called the molecular clock — where they analyze the rate of genetic mutations to backdate when two species likely diverged — say that available evidence points to sponges emerging much earlier, around a billion years ago.

Yet no supporting physical evidence has yet been found until now.

I’ve done a little fossil hunting in Utah and Wyoming, though most of the fossils I’ve dug up there are only about 50 million years old. The issue with finding much older fossils is that the Cambrian is when animals first developed the kind of external shells, bones and cartilage that fossilize pretty well. But sponges don’t have any of those things which makes finding evidence of their existence in ancient rocks a pretty tough thing to do. In any case, it’s a pretty interesting argument about something that could turn out to be a game-changer for our understanding of life on earth.