Researchers working at a sedimentary rock formation in northern Labrador, Canada, say they’ve uncovered evidence of primordial life in 3.95 billion-year-old rocks. The discovery, which is already drawing scrutiny and some skepticism, suggests that microbial life emerged relatively quickly after the formation of our planet. 
 
 The idea that life could have emerged so long ago—and in such an alien environment—is nothing short of astounding. During the Eoarchaean Era, when Earth was just 500 million years old, our planet’s landscape was littered with volcanoes, and its newly-formed crust was still too hot to support tectonic activity. Asteroids and comets pounded the surface at an uncompromising pace, delivering the chemical building blocks required for life. Back then, Earth’s atmosphere was choked in methane and ammonia, without any free floating oxygen to speak of. Even the Sun looked different, shining down with a brightness around 75 percent of what we see today. 
 
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 It was in this hostile environment that early life had to emerge, take root, and survive. New evidence published today in Nature is offering further evidence that primordial Earth, despite these harsh conditions, was able to sustain life. Traces of biological activity locked inside badly-warped 3.95 billion-year-old sedimentary rocks may represent some of the earliest known examples of life on Earth, pushing back the origin of life by about 150 to 250 million years. 
 
 Finding evidence of primordial life isn’t easy, mostly because ancient rocks have been severely twisted and transformed over time. The oldest fossils date back about 3.77 billion years, but microbial organisms can leave behind other traces of their existence as well. 
 
 Prior to this discovery, some of the oldest evidence of life was detected in rocks from Greenland, including 3.7 billion-year-old rocks from the Isua belt and 3.8 billion-year-old rocks from the Akilia rock formation. But the rocks analyzed in this latest discovery, made by Tsuyoshi Komiya from the University of Tokyo, comes from the poorly studied Saglek Block in northern Labrador, Canada, which have been dated to about 3.95 billion years old. 
 
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 For the study, Komiya looked for biogenic (i.e. biologically produced) graphite grains locked within the rocks. These aren’t fossilized imprints of the microbes, but the stuff they left behind. Komiya and his colleagues conducted a detailed geological analysis of the rocks, while also measuring the chemical compositions of the graphite, which appeared to be indicative of biological processes. Importantly, they ruled out the possibility that the rocks were contaminated with younger rocks. The graphite contained within these 3.95 billion year old rocks, argue the researchers, is of biological origin, and thus suggestive of life. 
 
 “This is an excellent paper with lots of information and another definite proof that life existed back in the Eoarchean,” said Dominic Papineau, a researcher at University College London, in an interview with Gizmodo. “I think the authors make a solid case, although it could have been further compelling by looking at the elemental and molecular compositions of the graphite and the mineral associations with the graphite.” 
 
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 Papineau is concerned that the graphite may have been inorganically produced, and believes the researchers should have done more work to prove its biogenic nature. Matthew Dodd, a PhD student who works with Papineau at UCL, also likes the paper, but he shares the same concern. 
 
 “I agree with their conclusions based on this preliminary data. However, the study is somewhat limited in evidence for biogenecity of the graphite,” Dodd told Gizmodo. “The authors rely solely on the isotopic composition of carbon in the graphite, therefore it will take further analyses to provide conclusive evidence.” 
 
 Dodd says that the chemical signature detected by Komiya could have been produced by a variety of chemical processes without the need for biology. 
 
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 “Isotopically light carbon is found in meteorites, for example, and we know this is inorganic,” he said. “Future work will need to establish other lines of chemical evidence such as whether there are biologically critical elements such as nitrogen, sulphur and phosphorus within this graphite, for the biogenecity of the carbon to be properly assessed.” 
 
 Interestingly, Dodd says these findings could tell us something about how life emerged not just on Earth, but on other planets as well, including Mars. 
 
 “It narrows the gap of life’s emergence [on Earth] from between 4.3 billion (the age of the oceans— life requires water) to 4 billion years ago,” he said. “It provides a cross-roads to life’s occurrence elsewhere in the Solar System, since Mars is believed to have been similar to Earth at this point in time. Therefore, we should expect to find life on Mars four billion years ago if life is a straightforward process to kickstart. If we don’t find evidence for life on Mars at this time...then Earth is a special case in the solar system—and potentially the Universe.” 
 
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 Indeed, the fact that life got started so quickly on Earth, and under such stressful conditions, should lead us to believe that it’s a common occurrence throughout the Universe. But as Dodd points out, the longer we go without finding traces of life elsewhere—Mars included—the more we might start to think our planet has something special going on. 
 
 [Nature] ||||| Image copyright UOW Image caption Life's record: The wavy features were organised by microbrial activity, it is claimed 
 
 Some of the world’s earliest life forms may have been captured in squiggles found in ancient rocks from Greenland. 
 
 The rocks were part of the seafloor 3.7 billion years ago, and the wavy lines, just a few centimetres across, would be remnants of primordial microbial colonies called stromatolites. 
 
 The evidence is presented in the academic journal Nature. 
 
 If confirmed, the colonies would predate the previously oldest known fossils by over 200 million years. 
 
 To put that in context, travelling back a similar time from today would be to leap into the world of the first dinosaurs. 
 
 But all claims of extremely early life are hotly contested, and this find is as well. 
 
 The find was made in a desolate expanse of uplands that butt up against the Greenland ice cap, called the Isua Supercrustal Belt. 
 
 The host rocks were exposed only recently after permanent snow cover melted. 
 
 The region is famous in geoscience because it is the oldest surviving piece of the Earth’s surface. 
 
 Image copyright SPL Image caption Go to Shark Bay, Australia, today and it is possible to see see modern stromatolites 
 
 And in the late 1990s, Minik Rosing, a native Greenlander and professor of geology at the Natural History Museum of Denmark, identified chemical traces of life in its rocks – layers of carbon that had evidently once been part of living bacteria (although this interpretation has also been contested). 
 
 Prof Rosing suggests those bacteria lived in the surface of the ocean, capturing sunlight and photosynthesising, until they died and “rained down” to the seabed. 
 
 The layers of carbon are interleaved with volcanic ash that may have come from a nearby island. 
 
 The stromatolites described by Martin van Kranendonk and colleagues in this week’s issue of Nature would have lived in a quite different way. 
 
 Stromatolites are effectively living rocks formed of mineral grains glued together by sticky, colonial bacteria. 
 
 They are rare today – the best known are in the harsh waters of Shark Bay, Western Australia, where bacteria slide up through each new layer of sediment washed up by the tides. 
 
 Similar mounds found in the Western Australian outback are currently the oldest acknowledged fossils on the planet, at 3.48 billion years old. 
 
 The older examples now claimed for Greenland appear to be remarkably similar, says Prof van Kranendonk, an early-Earth expert at the University of New South Wales. 
 
 “We see the original unaltered sedimentary layers, and we can see how the stromatolite structures grow up through the sedimentary layering. And we can see the characteristic dome and cone-shaped forms of modern stromatolites.” 
 
 Image caption Minik Rosing's own claim for ancient life traces at Isua is also contested 
 
 The fossil structures are overlain by another thick layer of sediment – a sign the bacterial mats were fatally buried by mud or sand, perhaps during a storm. 
 
 “There’s plenty of evidence this was a shallow-water environment,” Prof van Kranendonk suggests. 
 
 “We can see the sands and rocks were moved around by energetic waves.” 
 
 The stromatolites themselves are limestone – precipitated out of the coastal waters by the original microorganisms, more evidence the researchers say that these are truly ancient. 
 
 There are no traces of the original microbes, only the mounds they built. But that is still incredibly important, says Prof van Kranendonk. 
 
 “This helps us think about how life developed on Earth, how fast that process was. It pushes everything back a little further, narrows the window between when we know nothing, and when we begin to know something.” 
 
 Prof Rosing, however, disagrees with almost every aspect of the analysis. The claim, he says, depends on the belief the samples come from a rare, well-preserved part of the original seabed. But since they were first part of the Earth’s surface, the Isua rocks have been twisted, stretched, crushed, and cooked by tectonic forces; the region is a geological “train-wreck” in the words of another geologist. 
 
 For example, Prof Rosing argues, the carbonate minerals far from being original biological precipitates, were produced far later, by reactions involving scalding soda water deep in the Earth’s crust. 
 
 The lines showing internal laminations, said to be primordial sedimentary layers, actually show where those waters percolated through the buried rocks. As for the dome- and cone-forms of the fossils, those are typical shapes seen where rocks of different strengths have been squeezed and stretched. 
 
 “It’s clear from the pictures in the paper that these are highly deformed rocks,” Prof Rosing told the BBC. 
 
 Image caption Current record: The fossil stromatolites at Pilbara in Australia are about 3.5 billion years old 
 
 The problem is familiar in early Earth science – so much has happened to the rocks over geological history, it is hard to know what is original and what is an overprint by later processes. 
 
 Many claims of early fossils have fallen on close examination. Only a few survive the intense scrutiny of peer review. 
 
 Prof van Kranendonk stands by his argument that amidst the overall punishment suffered by the Greenland rocks, small pockets have survived well preserved – including the outcrop at the heart of this dispute. 
 
 “They’re just exceptional windows of preservation, which give us the keys to what happened so long ago.” 
 
 Geobiologist Michael Tice from Texas A&M University, US, who refereed the paper and approved its publication, takes a half-way position. 
 
 “The trouble with this kind of science is you’re trying to look at life after geology has done all the nastiest things to it. You’re limited by nature. The study is not definitive, but the evidence has passed all the tests they could apply. 
 
 "The point of publication is to stimulate more effort to find other examples.” 
 
 Prof Rosing agrees that a joint visit to examine the rocks in their original setting in Isua would be the best way to resolve the dispute. And Prof van Kranendonk hopes there may be further examples, older ones even, in the Greenland record. 
 
 What unites them is the belief that almost as far back as the rock record goes, life had already taken hold on the Earth. And the desire to know more about what that life was like. 
 
 Prof van Kranendonk can be heard discussing the new find on this week's Science In Action programme on the BBC World Service.
– Researchers say they've found fossilized bacteria that may date back to shortly after the formation of the Earth (geologically speaking, anyway), the New York Times reports. They published their findings Wednesday in Nature. The rocks were collected in 2008 from the Nuvvuagittuq geological formation in Canada. The rocks are estimated to have formed near a hydrothermal vent on the seafloor between 3.77 billion and 4.22 billion years ago. They contain tiny filaments and tubes, some connected by knobs, that resemble younger bacteria fossils created near hydrothermal vents. They also contain a level of carbon indicative of a living organism. If the fossils are what researchers say they are—and not everyone is convinced they are—they would push the date of earliest known life back billions of years. Currently the oldest fossilized bacteria widely accepted as legitimate are 3.5 billion years old and come from Australia, Ars Technica reports. And if these Canadian fossils are closer to 4.22 billion years old, it means the bacteria would have been alive just 340 million years after the formation of the Earth. Still, every new claim of finding the world's oldest fossilized life is met with skepticism, and this discovery is no different. One expert calls the rocks "dubiofossils," fossil-like but not clearly evidence of an organism. In response, researchers argue there's too much evidence in favor of their conclusion to ignore. (This dinosaur fossil is one of the "saddest" ever found.)