The study of life’s history on Earth is an ongoing effort to follow the thread further and further back in time. As amazing and fascinating as a few billion years’ worth of fossils are, we still ultimately want that Holy Grail that illuminates the origins of life on Earth. Unfortunately, that goal collides with the fact that the earliest evidence stands the least chance of being preserved through the eons for us to find. 
 
 Each new find that purports to supplant the earliest known signs of life is virtually guaranteed to be controversial, subject to poking and prodding from skeptical scientists uncertain that every competing (non-living) explanation can be ruled out. Last August, for example, a paper claimed to show the remnants of stromatolites (small mounds built by communities of shallow water microorganisms) in 3.7 billion-year-old rocks in Greenland. Similar fossils from Australia that come in at about 3.5 billion years old are generally accepted as legit, but anything older is still subject to scientific debate. 
 
 Now, a new study led by University College London PhD student Matthew Dodd describes evidence of what the researchers believe to be seafloor bacteria that lived at least 3.7 billion years ago. 
 
 That evidence comes from rocks that are part of Quebec’s Nuvvuagittuq belt, which contain some of the oldest rocks on the planet. They comprised an ancient seafloor made of volcanic rock, but there are also layers of iron minerals that precipitated out of the seawater. Those are believed to have formed near hydrothermal vents that gushed super-hot water laden with minerals. The Nuvvuagittuq rocks have proven hard to date, but they are known to be at least 3.77 billion years old, and could even be as old as 4.28 billion years—very early indeed, considering that our planet formed only a little over 4.5 billion years ago. 
 
 This is all further complicated by the fact that the Nuvvuagittuq rocks were metamorphosed under high temperature and pressure about 2.7 billion years ago. But within some jasper in the hydrothermal vent layers, the researchers found tiny tubes and filaments filled with hematite, an iron oxide mineral. The size and shape of these structures was fairly consistent (especially considering the metamorphic torture they’ve endured), and some pairs of tubes were connected by small “knobs.” 
 
 All this, the researchers say, is consistent with iron-oxidizing bacteria that we find at hydrothermal vents today, as well as slightly less ancient fossil examples. These bacteria build iron-oxide tubes around themselves and extend filaments out into their surroundings. 
 
 Around these familiar-looking structures, there are some even tinier bits of carbon-rich material here and there. The ratio of different carbon isotopes that are present is one good way to tell biological carbon from other sources, as organisms have a preference for lighter isotopes. In this case, the carbon that can be found in the rock does fall within the biological range—“although not unambiguously," the researchers write. 
 
 There are also some blobs ringed with magnetite, which have been seen in other rocks recognized to contain these sorts of fossils. Several minerals can be found within the blobs, which also contain bits of carbon-rich material. The researchers think that this set of minerals reflects reactions between organic matter and the iron precipitating from the hydrothermal vents—supporting a biological origin. 
 
 If the researchers are right about what they’ve found, this would be the oldest direct evidence of life we’ve ever seen. What’s more, if the recent discovery of stromatolites in Greenland also turns out to be the real deal, we would be able to say that there were at least two very different types of microorganisms living in very different parts of the ocean by 3.7 billion years ago. 
 
 This new paper is particularly interesting because it involves hydrothermal vent environments, which have been proposed as a logical place where life on Earth could have had its origins. Any evidence supporting that idea also makes hydrothermal vents on other worlds look more and more like priority targets in the search for life beyond our home planet. 
 
 Of course, it’s best not to get too carried away in daydreams until we’re more certain about what the researchers have found in these Canadian rocks. But the University of Western Australia’s David Wacey, who was not involved in this new study, told Ars that the multiple lines of evidence presented make a pretty strong case. “The morphological comparisons with younger vent-dwelling organisms are quite striking and it is rather difficult to envisage how the microstructures shown [in the paper] could be formed in a purely abiotic scenario. 
 
 “There will, no doubt, be arguments, and it may be many years before a consensus is reached, but this is how science progresses," Wacey added. "I think it will be particularly important to understand more about the regional geology of the area and perhaps try to better constrain the age of these potential organisms. 
 
 “The other exciting aspect of this report is that these potential microfossils are from a rock unit not previously studied for early life,” he continued. The Nuvvuagittuq rocks might even be older than the rocks researchers have been looking at in Greenland, South Africa, and Australia, and they represent a different marine environment, too. “This new study once again gets us thinking about a potential hydrothermal cradle of life.” 
 
 Nature, 2017. DOI: 10.1038/nature21377 (About DOIs). ||||| They are microscopic artwork: tiny tubes and long filaments, strange squiggles etched into some of the most ancient rocks known. 
 
 On Wednesday, researchers reported that these may be the oldest fossils ever discovered, the remains of bacteria thriving on Earth not long, geologically speaking, after the very birth of the planet. If so, they offer evidence that life here got off to a very early start. 
 
 But many experts in the field were skeptical of the new study — or downright unconvinced. 
 
 Martin J. Van Kranendonk, a geologist at the University of New South Wales, called the patterns in the rocks “dubiofossils” — fossil-like structures, perhaps, but without clear proof that they started out as something alive. 
 
 Heated disputes are nothing new in the search for the earliest life on Earth. In 1993 J. William Schopf, a paleontologist at the University of California, Los Angeles, and his colleagues found what that they, too, argued were the world’s oldest fossils: chainlike blobs in 3.46 billion-year-old rocks made, they said, by bacteria. Other researchers later argued that the structures were just oddly shaped minerals. ||||| 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]
– 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.)