January 2, 2013
Scientists Find Oldest Fossils On Earth, Evidence Of Life 3.49 Billion Years Ago
Brett Smith for redOrbit.com - Your Universe Online
In a sun-scorched region of Western Australia known as Pilbara, a team of American and Australian paleobiologists believe they have located the oldest known evidence of life on Earth. The ancient bacterial fossils have been dated as 3.49 billion years old, only about a billion years after scientists estimate the Earth was formed.
According to the findings presented by the joint team at the most recent meeting of the Geological Society of America, the tiny ridges that lattice the rocks like a fishing net seem to indicate that primitive bacteria integrated themselves into expansive networks. This collective behavior, which mirrors that of modern bacteria, involved thousands of different bacteria species, each performing a unique task that contributed to the larger community.
One of those communal functions was responsible for leaving behind traces of the bacteria for billions of years. Like some species of modern bacteria, thick mats of the microbes ensnare and fasten together sand particles. This adhesive layer of particles prevents erosion, resulting in rock fossils that outlast the living organisms that once lived there.
The team´s excitement over finding record-breaking ancient fossils, however, is tempered by the fact that scientists have been fooled by similar rock formations in the past. In 1980, comparable rippling layers were found in Australia´s Strelley Pool, over 180 miles to the north. However, Oxford University scientists later showed that water flowing along a seafloor can create similar structures under the right conditions.
In order to substantiate the most recent findings, the Australian-American team tested the idea that the formations were created by bacteria by measuring the carbon that makes up the textured rocks. Carbon-13, or “organic” carbon, found in the correct ratio showed that the formations in the Australian rock were most likely formed by bacterial activity.
“It´s always nice to have a number of different lines of evidence, and you definitely want to see organic carbon,” said geomicrobiologist John Stolz of Duquesne University in Pittsburgh.
Despite the strong evidence provided by the carbon analysis, the scientists were unable to identify proteins, fat or body fossils that would prove beyond a doubt that bacteria created the rock formations. That type of direct evidence would also help to identify which types of bacteria left behind the organic carbon.
Scientists noted that identifying the nature and type of these ancient bacteria would add an important puzzle piece for helping us to understand the story of how life first emerged on Earth.
“Studying this kind of past life is really about learning how the Earth got to be the way it is today,” said Michael Tice, a geobiologist at Texas A&M University.
In addition to helping biologists flesh out the details of Earth´s past, researching ancient bacteria could help scientists look for evidence of life on Mars, where NASA´s Curiosity rover has recently found evidence of life-supporting water. Additionally, the lack of tectonic activity and the Martian environment make the possibility of finding preserved bacterial fossils much greater than here on Earth if, in fact, it ever existed there.