Scientists working in Quebec’s Inuit territory have discovered what they believe to be the oldest fossils on record. Said to be between 3.8 and 4.3 billion years old, the fossil find would put the beginning of life on Earth nearly a billion years earlier than previously assumed.
The story of planet Earth began with the formation of the solar system about 4.6 billion years ago with the birth of the Sun and the gradual accumulation of leftover gases and dust into the planets that we know of today. By 4.54 billion years ago, the Earth had formed into a hot, volcanically active mass of molten rock, which then, as the Earth began to cool and water vapour condensed to form the oceans (roughly around 4.4 billion years ago), created conditions ripe for the emergence of life in the form of single-celled organisms.
But the timing of Earth’s life-changing event is still up for debate, with discoveries in recent years seemingly pushing back the start date to soon after the Earth’s oceans were formed.Scientists had previously granted the “oldest fossil” title to evidence found in Western Australia,dated at 3.5 billion years ago. Then with the discovery last year of layered rock formations called stromatolites in Greenland dating to 3.7 billion years ago, the timeline was pushed back another 220 million years.
Now, researchers claim to have found microbial activity from as early as 4.28 billion years ago in rocks found in the ancient Nuvvuagittuq Supracrustal Belt south of Inukjuak, Quebec. As published in the journal Nature, an international team of scientists from the UK, Norway, Australia, the United States and Canada says that iron-rich sedimentary rocks bear trace remains of bacteria that had once lived underwater near thermal vents and used chemical reactions involving iron to sustain themselves.
“It gives us a really great window, to understand how Earth was like back then, and in these rocks, we have actually identified the oldest traces of microorganisms that have lived on our planet,” says geologist Jonathan O’Neil of the University of Ottawa to APTN News.
The tiny fossils are made up of filaments and tubes up to a half a millimetre in length found within an iron-rich form of quartz called jasper. The researchers say that the distinctive patterns of the filaments are similar to structures made by iron-oxidizing bacteria in hydrothermal vent environments today and, coupled with the presence of other minerals like apatite and carbonate, known to be associated with biological activity, they provide proof that life existed at such an early age.
The researchers see their results as not only giving a glimpse of Earth’s own past but also aiding in our ability to draw parallel conclusions about the evolution of life on other planets, including Mars. "These discoveries demonstrate life developed on Earth at a time when Mars and Earth had liquid water at their surfaces, posing exciting questions for extra-terrestrial life," says Matthew Dodd, PhD student in the Department of Earth Sciences at the University College London, and study co-author said in a release. "Therefore, we expect to find evidence for past life on Mars 4,000 million years ago, or if not, Earth may have been a special exception."