The more experts explore the origins of life on Earth, the more surprising discoveries are made.

According to experts, long before humans appeared on Earth, life forms called this planet home some 3.5 billion years ago. That’s billion, not million.

For decades have scientists debated over the origins of life, and the oldest life forms to call our planet home.

Now, a new study published in the Proceedings of the National Academy of Sciences used state-of-the-art techniques to date the oldest organisms on Earth.

“The study describes 11 microbial specimens from five separate taxa, linking their morphologies to chemical signatures that are characteristic of life. Some represent now-extinct bacteria and microbes from a domain of life called Archaea, while others are similar to microbial species still found today. The findings also suggest how each may have survived on an oxygen-free planet.”

Their results revealed that bacteria and microbes had already developed on our planet staggering 3.5 billion years ago, and may have lived on Earth for a long time without—or very limited—oxygen.

The groundbreaking study was led by paleo-biologist William Schopf from the University of California-Los Angeles and geoscientist John Valley from the University of Wisconsin-Madison.

Researchers analyzed now-extinct bacteria and microbes which were discovered in 1982 at the Apex Chert, a rock formation located in Western Australia.

The organisms were found in the rock.

A heated debate that has lasted for more than two decades

The first ‘controversial’ results were obtained by Professor Schopf and his team in 1993, when, using radiometric analysis, they were able to date the fossilized organism to 3.45 billion years ago.

The rock Schopf and his team analyzed turned out as the earliest evidence of life on Earth, and Schopf and his team inferred that ‘creatures’ might have existed on Earth a billion years earlier than anyone previously thought possible.

These claims raised numerous doubts as other experts argue that Schopf’s claims were way too speculative and that the organisms he had found—invisible to the naked eye—were nothing more than weirdly shaped rocks, strange minerals that only resembled biological organisms, but were ultimately not.

However, more than two decades have passed since Schopf made the discovery, meaning that technology has greatly improved since then.

Professor Schopf found new ways to analyze the rock specimen after having developed new, revolutionary methods.

As noted by experts, any type of organic substance has a characteristic mixture of carbon isotope. Therefore scientists have identified new methods to discover the differences between organisms. Sing a very rare tool, a secondary ion mass spectrometer, experts managed to separate the carbon contents in each fossil into isotopes. This allowed them to measure the carbon-isotope makeup of each separate fossil, and compare it to fossil-less rocks from the same era.

Modern technology helps confirm a theory from the 1990’s

After measuring the carbon-isotope makeup of each separate fossil, Schopf and his team found how the difference in carbon-isotope ratios between the fossils and fossil-less rock, meaning that their theory from 1993 was right.

The rock, which was dated (radiometrically-dated) as being 3.5 billion years old was proven to contain the remains of early biological life as old as the rock the organisms were found in.

Schopf and his colleagues connected specific carbon-isotope ratios to specific fossil shapes, which helped them identify various ancient organisms.

They then analyzed the microfossils individually, and identified five species out of which two were identified as photosynthesizers, two were methane-consuming organisms, and one a methane-producing organism.

Source: Oldest fossils ever found show life on Earth began before 3.5 billion years ago

Reference: J. William Schopf, Kouki Kitajima, Michael J. Spicuzza, Anatoliy B. Kudryavtsev, and John W. Valley. SIMS analyses of the oldest known assemblage of microfossils document their taxon-correlated carbon isotope compositions. PNAS, December 18, 2017 DOI: 10.1073/pnas.1718063115

Quartz, Scientists finally confirm there was life on Earth 3.5 billion years ago