Microorganism Fossil
This is a 3.465 billion year-old fossil microorganism from Western Australia that was analyzed by researchers. J. William Schopf/UCLA Center for the Study of Evolution and the Origin of Life

If you firmly believe god created man and other living species on Earth, while leaving the rest of the vastness of the universe entirely barren of life, for reasons best known to god alone, this story may not be for you. But if you believe life formed on our planet (or was brought here from elsewhere early on) through natural processes, there is now more support for the theory that the same phenomena may have played out in other places in the universe as well.

Scientists analyzed the oldest-known fossils of microorganisms that date back almost 3.5 billion years ago, and were found in Western Australia. The new analysis of the fossils, led by researchers from the University of California, Los Angeles (UCLA), and University of Wisconsin-Madison (UW), used a technique called secondary ion mass spectroscopy (SIMS). It showed that of the five species, two were carrying out an ancient form of photosynthesis, one was likely producing methane while the other two were apparently consuming methane and using it to build cell walls.

While this discovery is evidence for the earliest-known life on Earth, it also raises another very exciting possibility — that of the commonality of life elsewhere in the universe. After all, these microorganisms lived at a time when Earth was very different from how it appears to us today — for instance, the planet had hardly any oxygen. And if those life forms could take birth here, there is no good reason why they (or other organisms like them) couldn’t have formed on other planets.

“By 3.465 billion years ago, life was already diverse on Earth; that’s clear — primitive photosynthesizers, methane producers, methane users. 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,” J. William Schopf, a professor of paleobiology in the UCLA College, and the study’s lead author, said in a statement Monday.

Talking about how the existence of relatively complex microorganisms meant life itself began on Earth even earlier (the first liquid water oceans on the planet existed as far back as 4.3 billion years ago), he added: “If the conditions are right, it looks like life in the universe should be widespread.”

Schopf is responsible for first reporting these microorganisms, which he described in a paper in the journal Science in 1993. But his findings were disputed at the time, with some critics saying they were oddly shaped minerals that merely looked like biological matter. The SIMS analysis has put that argument to rest, by showing differences in carbon isotopes.

“The differences in carbon isotope ratios correlate with their shapes. If they’re not biological there is no reason for such a correlation. Their C-13-to-C-12 ratios are characteristic of biology and metabolic function,” John Valley, professor of geoscience at UW and an author on the new study, said in a statement Monday.

Titled “SIMS analyses of the oldest known assemblage of microfossils document their taxon-correlated carbon isotope compositions,” the paper appeared online Monday in the journal Proceedings of the National Academy of Sciences.