By most accounts, Earth is believed to be about 4.5 billion years old. There has long been a debate on when life on our planet first started, but a new study might have settled that debate once and for all, as it confirms that the world’s oldest fossils are close to 3.5 billion years old. But aside from providing the earliest direct proof of life on Earth, the study could also lend credence to theories that extreme atmospheric conditions are not a hindrance to potential alien life forms on other planets.
According to Phys.org, a team of researchers from the University of California in Los Angeles and the University of Wisconsin-Madison analyzed 11 microbial specimens from an ancient piece of rock in Western Australia and linked them to certain chemical signatures that are associated with life. Study lead author J. William Schopf, a paleobiologist at UCLA, had first discovered the “microfossils” — named as such as they cannot be seen by the naked eye — in 1993, publishing his findings in the journal Science at that time. He then published another paper corroborating the microfossils’ biological existence close to a decade later, in 2002.
As further noted in the study published Monday in the journal Proceedings of the National Academy of Sciences, Schopf’s latest research confirmed that the world’s oldest fossils are biological in nature, as opposed to being “odd” minerals that merely look similar to biological specimens, as critics had once claimed. This was determined after the researchers studied carbon isotope ratios within each of the microfossils, and compared them against known carbon isotope standards and a section of rock from the same site that didn’t contain any proof of fossils.
A press release from UCLA explained that the world’s oldest fossils are believed to be 3.465 billion years old, with two of the species having shown what could be proof of “primitive” photosynthesis, two other species building their cell walls by consuming methane, and another one creating its own methane gas.
“These are the first data that show the very diverse organisms at that time in Earth’s history, and our previous research has shown that there were sulfur users 3.4 billion years ago as well,” Schopf added.
UW-Madison geoscience professor John W. Valley, another author on the study, was quoted by Phys.org as saying that the findings represent a “primitive, but diverse” group of microorganisms, one that is definitely biological, as evidenced by their carbon isotope ratios.
Interestingly, the world’s oldest fossils existed at a time when oxygen was barely present in our planet’s atmosphere, and while oxygen is considered to be one of the key ingredients of life, Schopf believes that the element would have been fatally toxic to the microorganisms. And since Valley’s UW-Madison team had previously theorized that Earth might already have had liquid water oceans about 4.3 billion years ago, the researchers believe that it’s not impossible for life on Earth to have been present as early as then.
“[The study] tells us [that] life had to have begun substantially earlier and it confirms that it was not difficult for primitive life to form and to evolve into more advanced microorganisms,” Schopf commented.
As noted in a report from Newsweek, the world’s oldest fossils might be an example of “extremophiles,” or creatures that actually thrive in conditions where temperatures and chemical levels are intolerable to humans. Assuming the microorganisms were indeed able to thrive in a young Earth that was extremely hot and oxygen-free, this could be a sign that planets and their moons with similar temperatures or atmospheric ingredients could theoretically harbor alien life. This was expressed by Schopf in the UCLA press release, as he believes his team’s findings suggest a chance of primitive life forms existing in other parts of the universe.