YouTube helped solve an evolutionary mystery that's puzzled biologists for decades

• Fabian Weston makes videos of tiny organisms filmed under a microscope.
• One of his videos provided the missing piece to link 400-year-old fossils with living euglenoids.
• Euglenoids may be some of the earliest eukaryotes, the domain that includes plants and animals.

Sometimes, it really does help to Google it. Especially when you're a stumped scientist who's exhausted all other angles.

That's what one research team did after all else had failed. And it helped them solve a scientific mystery that's confused biologists for decades.

400-million-year-old microscopic fossils

There have been five mass extinctions on Earth. Some events killed off 95% of living species. Euglenoids survived them all.

"Euglenoids are microscopic life forms that combine both animal and plant traits," Bas van de Schootbrugge, a geosciences professor at Utrecht University, told Business Insider via email. They eat like animals and photosynthesize like plants.

You can find the organisms in freshwater ponds all around the globe, van de Schootbrugge said. But they're rarely found in the fossil record, even though they've been around for eras.

To find ancient evidence of euglenoids, van de Schootbrugge and his colleagues looked at microfossils — teensy fossils that are only a few millimeters in size.

"We worked on a hunch that these microfossils could be cysts of euglenoids, but no one had ever seen a euglenoid make a cyst in nature or in a lab," van de Schootbrugge said.

Dating back 400 million years, some euglenoids made cysts that protected the organism during unfavorable conditions. But it was unclear what these cysts looked like.

A chance viewing of a YouTube video helped van de Schootbrugge and his colleagues link the fossils and living euglenoids.

The finding could help establish euglenoids as some of the earliest ancestors of all living plants and animals.

The proof was in a pond (and on YouTube)

There were two main problems with the cyst microfossils: what they were called and what they looked like.

"People working in different time slices had basically given different names to the same kind of microfossils, obscuring their long evolutionary history," van de Schootbrugge said.

They were Paleozoic Chomotriletes, Mesozoic Pseudoschizaea, and Cenozoic Concentricystes. The researchers went through 500 papers to find mentions of all the different names.

Other scientists had noticed the similarities between all these microfossils, but "the cysts have a structure that is unlike anything that has been seen before," van de Schootbrugge said. Since no one had ever documented a euglenoid making a cyst, there was nothing from the present to compare the ancient examples to.

And then one of van de Schootbrugge's co-authors, Paul Strother, Googled "Euglena cysts" and a result on YouTube popped up.

In the video, Fabian Weston was showing a sample of pond water under a microscope. The New South Wales resident has a YouTube channel devoted to filming all sorts of microscopic organisms.

In the video below, you can see the Euglena form into a ball with a thick, ribbed wall. "The cysts look layered, and this may be constructed from the mucus that is typically on the outside of certain euglenoids," van de Schootbrugge said.

"After watching it, we were convinced that what was seen in the video is Euglena making the kind of structure we see as microfossils," van de Schootbrugge said.

It was the missing piece.

"What we did, really, was to make the connection with the most recently living forms, which tied the taxonomic names to the living microorganisms," Strother told Business Insider via email.

They recently published their paper in the peer-reviewed journal Review of Palaeobotany and Palynology.

Van de Schootbrugge noted that they haven't yet seen Weston's cysts themselves and hope to go look at the pond's sediment for Chomotrilete microfossils.

The evolutionary tree of life

Strother thinks this study is a piece of the puzzle regarding the eukaryotic Tree of Life (eTOL). Eukaryotes are the domain of organisms that all animals and plants belong to. Unlike bacteria, their cells have a nucleus.

In other words, they're some of our earliest eukaryotic ancestors.

Scientists think euglenoids could have evolved over a billion years ago, according to a press release about the study. Knowing which eukaryotes evolved first would be a huge step in understanding how they've survived for so long.

Extending euglenoids' fossil records this far back in geological time suggests that they're among the oldest eukaryotes, Strother said, adding that "the question that this work addresses — but does not necessarily 'answer' — is, 'Which species are at the root of the eTOL?'"