If diversity is the spice of life then our planet may have become spicy at a remarkably young age, according to new research. After analyzing tiny filaments in an ancient chunk of seafloor sediment, scientists conclude that cosmopolitan populations of microbes may have existed just 300 million years after Earth formed, and suggest that similar primordial ecosystems might emerge equally quickly on other planets.
In Science Advances, researchers assessed a small piece of rock from the Nuvvuagittuq Supracrustal Belt (NSB) in Québec, Canada, which is estimated to be between 3.75 and 4.28 billion years old. Back in 2017, the team sparked a right biological barney by suggesting that the minute structures contained within this lump of jasper were caused by bacteria, thus pushing back the emergence of life on Earth by at least 300 million years.
Previously, the oldest purported fossils had been dated to 3.46 billion years ago, though some scientists contest the veracity of these ancient squiggles by arguing that they may have been produced by non-biological processes. Similarly, the NSB structures have been met with suspicion, prompting the researchers to take a closer look at these primeval structures.
To conduct their new analysis, the team dissected the rock into slices just 100 microns thin, and also created computerized 3D models of the imprints contained within their specimen. This allowed them to identify structures that were larger and more complex than those spotted in their previous analysis.
For instance, they noted tree-like stems with parallel branches, along with large numbers of distorted spheres known as ellipsoids. While similar shapes are known to be produced by chemical or geological processes, the authors explain that these non-biological arrangements tend to “have a smaller range of diameters… and a more organized distribution” than those seen in the NSB sample.
In contrast, they find striking similarities between the NSB structures and those produced by modern microbes living in undersea hydrothermal vents, such as those found near the Loihi submarine volcano off the coast of Hawaii or the Jan Mayen island volcano in the Arctic Ocean. Furthermore, the mineralized chemical by-products present in the rock mirror those produced by various other microbes, including those that metabolize iron, sulfur and carbon dioxide.
"Using many different lines of evidence, our study strongly suggests a number of different types of bacteria existed on Earth between 3.75 and 4.28 billion years ago," explained study author Dr Dominic Papineau in a statement. "This means life could have begun as little as 300 million years after Earth formed. In geological terms, this is quick – about one spin of the Sun around the galaxy."
The researchers’ conclusions are further supported by the fact that the structures appear to be better preserved in sections of finer quartz – which has been subjected to less extreme heat and pressure – than coarser quartz, which has experienced more intense force. This implies that the observed shapes are unlikely to have been caused by geological processes like metamorphism, and are were probably created by ancient life forms.
“This discovery implies that only a few hundred million years are needed for life to evolve to an organized level on a primordial habitable planet,” conclude the study authors. In terms of what this means for life in general, Papineau insists that "these findings have implications for the possibility of extraterrestrial life.”
“If life is relatively quick to emerge, given the right conditions, this increases the chance that life exists on other planets."