A team of Australian researchers from the University of Wollongong have possibly identified 3.7-billion-year old stromatolite fossils in Greenland, and they might pertain to the earliest signs of life on Earth. Found along sedimentary rocks in the Isua Greenstone Belt (along Greenland’s icecap), these stromatolite fossils predate the previously oldest known stromatolite fossils (originally found in Western Australia) by a significant 220 million years. In other words, the potential discovery could push back the fossil record, and thus the emergence of life on Earth, near the start of our planet’s own geological record.
And it’s not just any rudimentary life-form we are talking about. That is because, as opposed to an isolated single cell organism, stromatolite fossils comprise a complex network of carbonate constructed by communities of microbes. As lead researcher Allen Nutman said –
The significance of stromatolites is that not only do they provide obvious evidence of ancient life that is visible with the naked eye, but that they are complex ecosystems. This indicates that as long as 3.7 billion years ago, microbial life was already diverse. This diversity shows that life emerged within the first few hundred millions years of Earth’s existence, which is in keeping with biologists’ calculations showing the great antiquity of life’s genetic code.
Interestingly enough, the fossils were found in the world’s oldest known sedimentary rock, by the edge of Greenland’s icecap. Suffice it to say, these rock specimens were already being studied by researchers, but the fossils were hidden by prodigious amount of snowfall in the region. However this time around, the research team arrived at the fortuitous time to view these fossils. Consequently, the fossils were salvaged by precisely cutting them out (in tiny cones) from the rocky outcrop; and on preliminary analysis they revealed structures and layering that are very similar to both ancient and modern stromatolites.
Now from the scope of geoscience, the find – if proven, can significantly change the chronology of our evolutionary pattern. Simply put, considering the time required to evolve into organisms that entail stromatolites formations, life on Earth could have started during the Hadean stage, which encompasses a period between 4.6 billion – 4 billion years ago. However the scenario on our planet during much of this time was not at all conducive to lifeforms, due to relentless bombardments of asteroids. In fact, the very term ‘Hadean’ comes from Hades, the ancient Greek god of the underworld, in allusion to the hellish conditions on Earth at the time.
So the question naturally arises – how did life evolve through such ‘hellish’ conditions? To that end, the researchers still have to find credible supporting evidence that proves the connection of the fossils to such ancient lifeforms. As Abigail Allwood, an astrobiologist at NASA’s Jet Propulsion Laboratory, put forth the question –
If we found something like this on Mars would we stick a flag in it and call it life? I don’t think we would. Having said that, it’s incredible that anything can be found in these rocks that are barely a ghost of what they were before. That’s why it’s worthy of attention.
Intriguingly enough, with all the talk about Mars-based comparisons, the discovery of these potential fossils of ancient lifeforms could also shed new light into search for evidence of life on Mars. As Nutman explained –
We now have tangible visual signs of life on Earth in the same period that there was water on Mars. It’s not a huge assumption to say that any life on Mars at this time was also single-celled micro-organisms.
But of course before reaching any solid conclusion, the researchers have to look for additional signs of life in the proximate areas around the fossils. This would entail the deposit of organic matter that might have accompanied the stromatolite formations along with the ‘engineer’ bacteria.