Yet to be topped, this discovery by scientists out of UCLA and UW-Madison from 2017 still takes the cake for being the oldest known fossils in the world.
UW-MadisonA photo of the rock samples analyzed by UW-Madison researchers.
The Earth is full of clues to its past. Fossils are one way the planet provides a glimpse into the creatures and ecosystems that came before us. But how early do these records actually go?
According to a study published by the University of Wisconsin-Madison in conjunction with UCLA, a rock from Western Australia answers this question.
After examining the fossils inside of the rock, researchers have determined they are the oldest fossils ever found, dating back almost 3.5 billion years.
Microfossils Aren’t A New Discovery
J. William Schopf/UCLAOne of the microfossils found in the rock from Western Australia.
The small fossils found in the rock are known as microfossils, because they are so small that they’re invisible to the naked eye. In fact, each one of them measures just 10 micrometers wide – for scale, eight of them could fit along the width of a single human hair.
Microfossils were first noted in 1993, by UCLA’s J. William Schopf, lead author of the study and professor at UCLA. Schopf first described them in a science journal, after he was drawn to their unique cylindrical and filamentous shapes.
In 2002, he published another paper on them, suggesting they may be biologic entities, and not just mineral or geologic anomalies. However, much of Schopf’s early work was criticized and even disputed. Critics believed these microfossils to be odd minerals that only look like biological specimens.
J. William Schopf/UCLAProfessor and lead author of the study, J. William Schopf.
Schopf first found the rock that ended up containing the oldest microfossils in 1982 from a deposit in Western Australia. The fossils were preserved in the rock due to the region’s unique conditions, which lack the geological processes necessary to alter the evidence, such as extreme heat from tectonic plate activity and burial.
Today, any dispute over the legitimacy of these micro-organisms has been settled, John Valley declared, researcher from UW-Madison who was partnered on the project with Schopf.
Old Fossils Discovered Through New Methods
Jeff Miller/UW-MadisonJohn Valley and another researcher using the SIMS to analyze the fossils.
Schopf and Valley were able to identify these mico-organisms using a secondary ion mass spectrometer (SIMS) at UW-Madison. SIMS are machines that generate beams of ions in order to analyze organic compounds such as rocks, or in this case, fossils.
Fossils this old hadn’t been analyzed using SIMS before. It took Valley and his team nearly 10 years to develop a process to analyze and identify the samples, building off years of previous research.
Using SIMS, researchers were able to separate the carbon in each fossil into isotopes and measure the ratios. The ratios then helped to determine the fossils had once been living creatures.
Wikimedia CommonsAn example of a stromatolites rock sample, similar to the one analyzed from Western Australia.
The team was also able to assign identities to the fossils based on the isotope ratios, which show that they are “a primitive but diverse group of organisms” Schopf described. That group of organisms was, more specifically, micro bacteria. The results showed 11 different microbial specimens, from five separate organisms.
Some of the organisms were from a family known as Archaea, a group of bacteria that produced methane gas. Others were forms were of gammaproteobacteria, a group that consumes methane gas.
What These Fossils Tell Us About Our Planet And Beyond
Jeff Miller/UW-MadisonA sample of the 3.5 billion-year-old rock.
The biology of these micro bacteria add to the picture of what life on Earth was like billions of years ago.
The discovery of the gas producing and consuming organisms provide a window into understanding how life forms may have survived in an atmosphere that was low in oxygen.
Additionally, the researchers discovered phototrophic bacteria – bacteria that relied on the sun for energy. Again, this lends itself to research on how organisms could have survived in a climate entirely different than our own.
Schopf believes research like this can tell us a lot about not just our planet, but the entire universe. Considering the rough conditions these micro bacteria had to endure, it’s possible this model of life-form could exist elsewhere in the universe.
But the most important implications of this discovery indicate something larger for Earth, Schopf clarified. If a diverse range of micro bacteria already present 3.5 billion years ago, who knows when the earliest life on Earth began.
John Valley/UW-MadisonA site in Western Australia near where the rock containing 3.5 billion-year-old fossils was found.
“Life had to have begun substantially earlier — nobody knows how much earlier — and confirms it is not difficult for primitive life to form and to evolve into more advanced microorganisms,” Schopf explained.
In previous research, Valley found that liquid oceans on Earth as early as 4.3 billion years ago, just 250 million years after the Earth formed.
“People are really interested in when life on Earth first emerged,” Valley said. “This study was 10 times more time-consuming and more difficult than I first imagined, but it came to fruition because of many dedicated people who have been excited about this since day one … I think a lot more microfossil analyses will be made on samples of Earth and possibly from other planetary bodies.”
There Could Be Older Fossils Out There
Matthew Dodd/PAA sample from the study out of UCL that suspects the oldest fossils in the world comes from Quebec, Canada.
What is really the oldest fossil specimen is still debated amongst researchers. While it is generally accepted that these fossils from Western Australia are the oldest, an earlier study suggests the oldest fossils found were 4.3 billion years old, inside rocks located in Quebec, Canada.
“Our discovery supports the idea that life emerged from hot, seafloor vents shortly after planet Earth formed. This speedy appearance of life on Earth fits with other evidence of recently discovered 3,700 million year old sedimentary mounds that were shaped by microorganisms,” head researcher of the study Matthew Dodd explained.
However, Valley claims that this study was not as concrete as his study with Schopf, but he is open to discovering more.
Jeff Miller/UW-MadisonProfessor and researcher John Valley in his office at UW-Madison.
“We have no direct evidence that life existed 4.3 billion years ago but there is no reason why it couldn’t have,” says Valley. “This is something we all would like to find out.”
Even before Schopf and Valley’s discovery, Australia was still home to one of the oldest fossils on Earth. In 2011, researchers at University of Western Australia found fossils 3.4 billion years old. Similarly to Valley and Schopf, the researchers used isotopes to analyze the fossil.
Researchers are still on the lookout for fossils older than 3.5 billion years old, but as of now the rock from Western Australia takes the cake.
Next, check out more interesting organisms that have been found during explorations into Australia. Then, check out some of the world’s oldest living fossils.
