Newly discovered fossils of bacteria discovered in melted snow in Greenland are believed to be approximately 3.7 billion years old, and if the find is confirmed, it would be evidence that life on Earth started more than 200 million years earlier than scientists had previously believed.
According to NBC News and the New York Times, these fossils, which were discovered by Allen Nutman from the University of Wollongong in Australia and his colleagues, are not actually the remains of the microbes themselves but stromatolites – formations created by bacteria when they established colonies shallow water and accumulated sand and other sediments
The newfound fossils were discovered in an ancient rock buried beneath a layer of snow in an outcrop known as the Isua supracrustal belt, Nutman’s team explained. Based on their analysis of the fossils, the researchers determined that they are 220 million years older than those discovered in the Pilbara Craton of Western Australia, which were 3.48 billion years old.
Researchers had previously determined that the Isua rocks had a chemical composition indicative of biological life, but skeptics argue that such a composition could have originated naturally, the Times noted. Gerald Joyce, an origin-of-life expert at the Scripps Research Institute in California, told the paper that the new study “provides the oldest direct evidence of microbial life.”
Discovery could have implications for the origins of life on Earth
Nutman and his colleagues, who have published their findings in the latest edition of the journal Nature, revealed that they actually discovered the fossils four years ago, but kept the find secret “because we wanted to present it in the most robust way we could manage.”
The rocks where the fossils were found is typically covered with snow, but in this case, that snow had melted and left a 98 foot by 230-foot portion of the formation exposed. The researchers studied the area and found multiple small cone-shaped structures, none more than 1.5 inches tall, that contained sediment layers similar to those found in modern stromatolites.
These stromatolites are the oldest fossils ever discovered. Credit: Allen Nutman
Given the nature of the discovery, there will be much discussion and debate before the authors’ claims that they have found the world’s oldest evidence of biological life are widely accepted by the scientific community, the Times noted. However, if confirmed, the Isua stromatolites would have been created by fairly evolved organisms, which Nutman believes indicates that life on the Earth would have had to have originated at an even earlier point in the planet’s history.
He suggests that the origins of life could be traced back to the Hadean eon, a stage of Earth’s history that lasted from its formation 4.65 billion years to around four billion years ago. This might seem unlikely, as conditions on the planet are believed to have been hellish enough for the age to have been named in honor of the Greek god of the underworld, Hades, but recent studies have suggested that things may not have been as bad as scientists originally thought.
Whether his latest discovery is verified or not, Nutman told the Times that there is a “diminishing probability” that any fossils older than these will be discovered. Rocks from this era are difficult to find, and even those that have survived often have been exposed to so much heat and so many other geological processes that all evidence of biological remains have been destroyed.
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Image credit: University of Wollongong
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