By Ed Yong
Back then, the landscape would have been very different. The Earth was a hellish place that had only just acquired a firm crust. Its atmosphere was devoid of oxygen, and it was regularly pelted with asteroids. There were no reindeer, whales, polar bears, or lichen. But according to new research, there was life.
In a rock formation called the Saglek Block, Yuji Sano and Tsuyoshi Komiya from the University of Tokyo found crystals of the mineral graphite that contain a distinctive blend of carbon isotopes. That blend suggests that microbes were already around, living, surviving, and using carbon dioxide from the air to build their cells. If the two researchers are right—and claims about such ancient events are always controversial—then this Canadian graphite represents one of the earliest traces of life on Earth.
Those fossils, from the Isua Belt in southwest Greenland, are stromatolites—layered structures created by communities of bacteria. And as I reported last year, their presence suggests that life already existed in a sophisticated form at the 3.7-billion-year mark, and so must have arisen much earlier. And indeed, scientists have found traces of biologically produced graphite throughout the region, in other Isua Belt rocks that are 3.8 billion years old, and in hydrothermal vents off the coast of Quebec that are at least a similar age, and possibly even older.
“The emerging picture from the ancient-rock record is that life was everywhere,” says Vickie Bennett from Australian National University, who was not involved in the latest study. “As far back as the rock record extends—that is, as far back as we can look for direct evidence of early life, we are finding it. Earth has been a biotic, life-sustaining planet since close to its beginning.”
This evidence hinges on a quirk of chemistry. Carbon comes in two stable isotopes—carbon-12, which is extremely common, and carbon-13, which is rarer and slightly heavier. When it comes to making life, carbon-12 is the more pliable building block. It’s more reactive than its heavier cousin, and so easier to transform into molecules like carbohydrates and proteins.
But are those graphite grains the same age? The rocks around them are metamorphic—they’ve been warped and transformed at extreme temperatures and pressures. During that process, and all the subsequent geological tumult that this region has experienced, it’s possible that much younger graphite somehow infiltrated the older rock, creating a false signal of early life.
To rule out that possibility, the Tokyo team looked at the structure of the graphite grains. The more orderly and crystalline those structures, the hotter the grains were when they formed. Based on that relationship, the team calculated the graphite was created at temperatures between 536 and 622 Celsius—a range that’s consistent with the temperatures at which the surrounding metamorphic rocks were transformed. This suggests that the graphite was already there when the rocks were heated and warped, and didn’t sneak in later. It was truly OG—original graphite.
There’s still room for doubt, though. Given how ancient these rocks are, and how much geological tumult they have experienced, it’s hard to fully exclude the possibility that the graphite got there later. Also, other processes that have nothing to do with living things could potentially change the ratio of carbon-12 and carbon-13. It’s concerning that the ratio varies a lot in the samples that the Tokyo team analyzed, says Andrew Knoll from Harvard University. But he also says that the team has been careful, and their combined evidence “makes a strong case that life existed on earth nearly 4 billion years ago.”
“The authors have done as many checks as they could for whether they are indeed analyzing 3.95-billion-year-old graphite rather than later contamination,” adds Elizabeth Bell, a geochemist from the University of California, Los Angeles. “They make a plausible case that the graphite is original.”
Bell herself found the oldest graphite that’s been measured to date. It lurked within a 4.1-billion-year-old zircon gemstone from Western Australia, and also contained a blend of isotopes that hinted at a biological origin. That discovery is also controversial, especially since the graphite was completely cut off from its source environment, making it hard to know the conditions in which it was formed.
Still, all of this evidence suggests Earth was home to life during its hellish infancy, and that such life abounded in a variety of habitats. Those pioneering organisms—bacteria, probably—haven’t left any fossils behind. But Sano and Komiya hope to find some clues about them by analyzing the Saglek Block rocks. The levels of nitrogen, iron, and sulfur in the rocks could reveal which energy sources those organisms exploited, and which environments they inhabited. They could tell us how life first lived.
By Henry Bodkin
the planet than previously thought because scientists got their modelling wrong, a new study has found. New research by British scientists reveals the world is being polluted and warming up less quickly than 10-year-old forecasts predicted, giving countries more time to get a grip on their carbon output.
An unexpected “revolution” in affordable renewable energy has also contributed to the more positive outlook.
Experts now say there is a two-in-three chance of keeping global temperatures within 1.5 degrees above pre-industrial levels, the ultimate goal of the 2015 Paris Agreement.
Paris climate change deal: Moment agreement announced
They also condemned the “overreaction” to the US’s withdrawal from the Paris Climate Accord, announced by Donald Trump in June, saying it is unlikely to make a significant difference.
According to the models used to draw up the agreement, the world ought now to be 1.3 degrees above the mid-19th-Century average, whereas the most recent observations suggest it is actually between 0.9 and 1 degree above.
The discrepancy means nations could continue emitting carbon dioxide at the current rate for another 20 years before the target was breached, instead of the three to five predicted by the previous model.
“When you are talking about a budget of 1.5 degrees, then a 0.3 degree difference is a big deal”, said Professor Myles Allen, of Oxford University and one of the authors of the new study.
Published in the journal Nature Geoscience, it suggests that if polluting peaks and then declines to below current levels before 2030 and then continue to drop more sharply, there is a 66 per cent chance of global average temperatures staying below 1.5 degrees.
The goal was yesterday described as “very ambitious” but “physically possible”.
Another reason the climate outlook is less bleak than previously thought is stabilising emissions, particularly in China.
Renewable energy has also enjoyed more use than was predicted.
China has now acquired more than 100 gigawatts of solar cells, 25 per cent of which in the last six months, and in the UK, offshore wind has turned out to cost far less than expected.
Professor Michael Grubb, from University College London, had previously described the goals agreed at Paris in 2015 as “incompatible with democracy”.
Outrage at Trump’s withdrawal from Paris climate agreement
But yesterday he said: “We’re in the midst of an energy revolution and it’s happening faster than we thought, which makes it much more credible for governments to tighten the offer they put on the table at Paris.”
He added that President Trump’s withdrawal from the agreement would not be significant because “The White House’s position doesn’t have much impact on US emissions”.
“The smaller constituencies – cities, businesses, states – are just saying they’re getting on with it, partly for carbon reduction, but partly because there’s this energy revolution and they don’t want to be left behind.”
The new research was published as the Met Office announced that a “slowdown” in the rate of global temperature rises reported over roughly the first decade of this century was now over.
The organisation said the slowdown in rising air temperatures between 1999 and 2014 happened as a result of a natural cycle in the Pacific, which led to the ocean circulation speeding up, causing it to pull heat down in the deeper ocean away from the atmosphere.
However, that cycle has now ended.
Claire Perry, the climate change and industry minister, claimed Britain had already demonstrated that tackling climate change and running a strong economy could go “hand in hand”.
“How is the time to build on our strengths and cement our position as a global hub for investment in clean growth,” she said.
By Alexandra King
Scientist and astrophysicist Neil deGrasse Tyson said Sunday that, in the wake of devastating floods and damage caused by Hurricanes Harvey and Irma, climate change had become so severe that the country “might not be able to recover.”