As an undergraduate student at the University of New South Wales, Dr Erica Barlow picked up a rock that would change her life and dramatically alter our view of the history of life on Earth. But it took a long time to work out what it was she had, and to this day, no one knows if the rock contained what Barlow and her colleagues suspected.
Barlow Western Australia Pilbara Region study Stromatolitessome of the oldest fossils we know of. The journey involved many long walks between campsites and the fossils. On one return trip, Barlow noticed a shiny black rock reflecting the setting sun on the area’s famous red soil. She picked it up as a memento of the trip. “I kept it on my desk as a kind of pet rock while I was writing the novel. [honors] Mr. Barlow said, statement.
While Barlow was still working on stromatolites, her supervisor, Martin van Cranendonk, noticed the rock and identified it as black chert, which he told her was known to contain microfossils of the early development of life on Earth. This is debatableBuried in papers, Barlow needed some encouragement to take the time to prepare and test samples, but when he did, he was amazed.
One of Barlow’s specimens that demonstrates its complexity.
Image credit: Erica Barlow
The fossils in the chert were like nothing Barlow had ever seen before. And no one else had seen anything like them. Given the age of the chert, if Microfossils The interior was expected to contain single-celled organisms. The microfossils Barlow found resembled footballs, roughly circular but with complex contours and an internal honeycomb structure.
“There’s nothing else like the microfossils I found in the geological record,” Barlow said.
The closest living analogue to what Barlow found appears to be certain algae, such as this sample. VolvocaseaThey are hollow structures surrounded by hair-like flagella, which are in turn surrounded by a thick, gummy substance called mucus.
Image credit: Antonio Guillen
This is a big claim in any context, but it’s even bigger when you consider that the chart was thought to be much older than that. A complicated life appears to have appeared.
The stromatolites Barlow studied contain thousands of cells that come together from their own bodies and sand to form layered structures, but they’re not what we think of as complex life forms.
As far as anyone knows, the first complex life forms were hundreds of millions of years younger than this discovery, and Barlow’s discovery may have been a precursor to eukaryotes, the branch on the tree of life that includes all animals. plantfungi, algae. Or maybe they are evolutionary dead ends, early blooms of complexity that have died out. Or maybe they are just illusions that mimic complexity in ways we can’t explain.
There was only one thing she could do: make the rock the subject of her doctoral thesis.
First, Barlow needed to know if the chert was unique. Returning to his collection site, the answer was soon clear: Barlow walked 30 metres (100 feet) up a nearby slope and found a rock wall dotted with thousands of black chert nodules. Like the Pilbara itself, the rock wall stretched out of view in both directions. Barlow told IFLScience that he has since measured the length of the rock formation at 12 kilometres (7 miles), all of which are packed with chert nodules averaging 20 centimetres (8 inches) wide and 7 centimetres (3 inches) high.
It’s a thin line through a vast area of the Pilbara, but the chert-containing formations extend beyond the horizon.
Image credit: Erica Barlow
Many chart samples include fossil Nothing out of the ordinary appears to be happening. Other life forms include “long, filamentous or single-celled, bubble-like” organisms similar to those found around the world at the time, Barlow told IFLScience. Scientists who take tiny samples could easily go home thinking nothing’s wrong.
But Barlow realised the potential importance of her discovery and the need to replicate it, so she collected hundreds of samples. Returning to Sydney, she found several specimens similar to the original, including one with an amber sphere inside a honeycomb shape. She now has 19 specimens, six of which were from a single rock. Among Barlow’s hundreds of samples are some that may have originally been similar, but are too deteriorated to be certain. If she had picked up one of these instead, she probably would not have realised its value.
Although this formation does not consist primarily of black chert, its modules are not difficult to find.
Image credit: Erica Barlow
The chert samples are apparently of the same age, and independent testing has confirmed that they all formed around 2.4 billion years ago – importantly, that matches the age that geologists are currently determining. After much discussion – for Great Oxidation EventAt this point, oxygen levels in the atmosphere and oceans increased dramatically, making breathable and opening the door to complex life.
Until now, there was an unexplained gap of about 750 million years between the time oxygen became available and the discovery of the first eukaryotic fossils, suggesting that something was using it.
Unfortunately, none of the specimens Barlow found were Eukaryotes.
“When dealing with materials from this period, it is very difficult to prove or disprove these things because not enough information has been preserved,” Barlow said in a statement.
The geneticist said:Molecular Clock“These estimates span a “very wide range” of when eukaryotes emerged, Barlow told IFLScience. Some of these estimates are close to the dates in her chart, but others are hundreds of millions of years later. “The problem with molecular clocks is that they’re based on the fossil record, so when we look back at this time when the fossil record is incomplete, it gets a little fuzzy,” she said.
In some places on Earth, 6 to 7 million years are represented.
Dr. Erica Barlow
In theory, chemical analysis could provide valuable evidence—“if we could identify the type of carbon, we might be able to tell us what the organisms were eating,” she says, potentially proving their complexity—but this is nearly impossible because samples would so easily be contaminated with carbon from the modern world.
“If we’re dealing with such small fossils, with such low carbon content, and we get good results, [scientific] “The local community won’t believe it because of the potential for contamination,” Barlow told IFLScience.
Future technological advances may improve this process, but for now Barlow’s work has been slow to be acknowledged, and the remoteness of the site may be part of the problem. Ediacara Hills In South Australia, many paleontologists were hesitant to believe it was real until they saw it, and because of the location it took a while to believe it.
If similar fossils were found elsewhere in the world, they could support Barlow’s claim, especially if they showed signs of further development at a later date. So far, none have been found, and Barlow admitted to IFLScience that this may be the only evidence we have. Early Experiments The complexity disappeared, never to reappear for a long time.
Meanwhile, the lack of another site isn’t entirely surprising, given how few places preserve fossils older than 1.6 billion years. “A handful of places on Earth have preserved fossils that are 600 to 700 million years old,” Barlow told IFLScience. Preserving fossil remains isn’t easy, but Barlow thinks the extreme scarcity may be due to plate tectonics conditions at the time.
If these specimens were eukaryotic ancestors, they wouldn’t look all that appealing by modern standards: “As far as we know, the organisms would have been soft, squishy and sticky — like the slime you find at the edge of a pond,” Barlow said in a statement. Still, van Cranendonk noted similarities to modern eukaryotic algae.
While she waited for something to break that would help her learn more about her discovery, Barlow completed a fantastically named postdoctoral research fellowship at NASA. Agnostic Biosignature LabSo she tried to devise a way to identify them. Life on other planets If it hadn’t looked like life on Earth, she might have had the best training in existence for such a mission.
Barlow’s latest research into this discovery has been published open access. Geobiology.
