Fossils Help Pin Down When Life Formed
Life formed on our planet some 3.8 billion years ago, likely in a warm, wet environment. It left behind fossils as proof of its existence. Knowing where life blossomed and exactly HOW long ago it happened has always been a moving target. We have to look for very old rocks, fossils, and even chemical evidence for the processes that define life.
The oldest life forms on the planet were all one-celled organisms. They flourished in the ancient oceans, attracted to hydrothermal vents (volcanic vents that spew mineral-rich and super-hot water from under the seabed). Now, teams of scientists have found ancient fossil evidence for life dating back possibly as far as 4.3 billion years ago.
What did they uncover? Tiny filaments and tubes formed by primordial bacteria that lived by eating iron. The rock layers where they were found lie in northern Quebec, Canada. These sedimentary rocks laced with quartz likely formed in the region of deep sea vents. The tiny life forms actually created little mounds of sediment that became fossilized.
Life and Its Habits
Life is a funny thing. Our planet is teeming with it, and evidence for it lies everywhere. It can be something as complex as the radio signals and light pollution we send streaming out to space, or as simple as the tiny hematite tubes left behind by one-celled animals. Like the investigators in the TV series CSI say, you just have to follow the evidence to figure out how that life lived and when. The existence of earliest life can tell us a lot about the conditions on Earth when it existed. These rocks, with their tubules and mineral formations, are clear evidence of primitive life
Life Changes a Planet
Other rocks on Earth also tell a tale of how our planet got its oxygen, as a by-product of life forms producing oxygen. These photosynthetic cyanobacteria took the carbon dioxide and other materials as part of their food chain. In return, they released oxygen. Much of the oxygen combined with dissolved iron in the oceans, which then settled into layers of mud that eventually hardened to stone. Iron oxides formed thin layers called “banded iron layers”. They exist around the world and tell a silent tale of life changing its environment (as it has done throughout history).
The recent discovery in Canada is now helping people pin down the dates of life’s earliest emergence with much more precision. It will be interesting to see if the researchers will find other, earlier rocks with evidence for ancient life forms showing up and evolving along with our planet.