Compared to fossils of extinct vertebrates, microbial fossils may not seem like much to look at, even when they’re highly magnified. Certain large fossil specimens are beautifully detailed in their preservation, retaining impressions of ancient animals’ skin or feathers. Others astonish with their sheer size, such as the giant sauropod dinosaurs’ massive femurs, which can be taller than a human adult.
But not everyone may agree that these fossils represent the oldest life on #Earth. Some experts have indicated that there are other samples that could be even older than the Australian #microfossils, while other researchers have cast doubt on whether these sediments house traces of life at all, suggesting that chemical markers thought to represent biological evidence were the result of geothermal activity.
However, when the authors of the new study used a novel method to inspect the delicate fossils on a molecular level, they detected certain carbon signatures indicating that the fossils were organic in origin after all. Though the fossils were estimated to be about 3.5 billion years old, the diversity of microbes in the group suggested that life probably emerged on Earth even earlier than that, the study authors reported. [In Images: The Oldest Fossils on Earth]
First unearthed in western Australia in 1982 and described in 1993, these microfossils are so tiny that eight of them lined up one after another would span the width of a human hair. The researchers who discovered the fossils initially identified them as biological, but other scientists argued that it was impossible to say for sure, proposing that the so-called “fossils” were more likely odd-looking minerals.
Ancient, preserved microbes that are too small to be seen with the naked eye, dating to billions of years ago, may represent the oldest known evidence of life on Earth, according to a new study.