Geologists are analyzing ancient clues to tell our origin story.
The rock is a deep rusty red, shot through with gray stripes. It rises above shrubby tundra, part of a hummocky terrain that slopes down to the Hudson Bay in northern Quebec, as it has for a very long time—maybe almost as long as the planet itself. This is a rare spot on Earth, one of a few where rocks this old survive. Plate tectonics and the relentless recycling of crust have repeatedly chewed up our planet’s surface. Only a few zones in deep continental interiors have escaped this fate, in places like Greenland and Western Australia. Scientists who specialize in finding signs of the origins of life make pilgrimages to these primeval sites. Life wrote its first chapters in these rocks. And scientists hope to read them.
Canadian geologist Dominic Papineau schemed for years to visit this lonely place, known as the Nuvvuagittuq Supracrustal Belt. In 2008, he finally rounded up a couple thousand dollars in funding and set out from the Carnegie Institution for Science in Washington, D.C., journeying through three layovers and a final leg on a bush plane. If you like rocks—and don’t mind mosquitoes—it’s a great place to ramble for a couple of weeks in the summer. A lichen-flecked stony expanse, polished by glaciers, juts through the thin soil.
Papineau pitched his tent near a creek. At that time of year, at these latitudes, the sun rises at 4 a.m., giving him many hours to explore. Three days before he was due to leave, Papineau found a 20- or 30-yard-long strike, part of a banded iron formation: reddish hematite layered with dark magnetite, like a red-and-gray napoleon. It had formed not too far from the location of an ancient deep-sea hydrothermal vent. Blobs the size of quarters dotted the surface, creating thin swirls. In younger rocks, Papineau knew, such marks can indicate the presence of former life. “When I saw this material, I knew I needed to sample it,” he says. With a sledgehammer, he smashed off chunks.
When it came time to go, he lugged his hundred-plus pounds of rocky souvenirs back to his lab at Carnegie, where he was a postdoctoral fellow in geophysics. There, his new specimens joined his collection and waited patiently as only rocks can until he could find time to analyze them.
Papineau finally dug in to investigate after he moved to University College London in 2014. Because the Nuvvuagittuq formation is believed to be between 3.77 billion and 4.28 billion years old, that would make his samples just slightly younger than our 4.54 -billion-year-old planet. Papineau and graduate student Matthew Dodd pursued a dozen lines of analyses and eventually concluded that these humble rocks held evidence of some of the oldest life ever found on Earth.
In March, they published their findings in the journal Nature. If correct, their work bolsters a newish theory in origins-of-life research: Rather than assembling its building blocks over a billion-plus years, the earliest forms burst forth in a geological heartbeat of tens of millions—maybe even hundreds of thousands.
Moreover, life may not have required freak coincidences. Rather, it might have formed as a routine consequence of Earth’s early chemistry, maybe a default set of conditions that can be found on rocky, wet planets everywhere—all 40 billion of them in the Milky Way alone.
But the origins-of-life field, like early Earth itself, is a cauldron of roiling theories, each new one challenged and sometimes buried under volcanic flows of criticism. If Papineau and Dodd are wrong—and some suspect they are—the marks and minerals they found are merely a mirage, another case of misleading geology that creates the illusion of long-ago microbes. And there will be consequences. Papineau jokes about Giordano Bruno, burned at the stake in 1600 for suggesting beings existed on other planets. Fortunately that form of peer review is no longer popular. Instead, they might endure the modern equivalent.
In 1992, Bill Schopf, of the University of California at Los Angeles, said he had found 3.5-billion-year-old microfossils in rocks from Western Australia. The claim survived for 10 years, until Martin Brasier, an Oxford astrobiologist and paleobiologist, charged that Schopf had misunderstood the rocks. And their geology. Brasier claimed Schopf had cherry-picked his evidence, and may even have committed fraud.
At that year’s Astrobiology Science Conference, the scientists hashed it out in public. In front of hundreds of origins-of-life and extraterrestrial-life researchers, Brasier and Schopf traded verbal blows, slamming each other’s science. The victory went to Brasier. Today, most researchers in the field do think that Schopf’s rocks showed evidence of early creatures—just not the type he thought he saw.
Almost since the 1870s, when Darwin first speculated that early life might have sheltered in a “warm little pond,” the field has given rise to nearly as many theories as there are scientists who specialize in this work. In general, though, the theories follow one of two themes: land or sea.
Biologists tend to prefer the sea theory, which posits that life began at deep-sea hydrothermal vents, where super-heated, mineral-charged water seeps up from inside the earth to nourish and sustain organisms. It seems reasonable. The sea could shelter early life from the relentless meteor strikes and deadly solar UV radiation that once scorched the young planet’s surface. And the vents would provide food, or energy, in the form of hydrogen gas and minerals such as sulfur and iron.
Michael Russell, who heads the planetary chemistry and astrobiology group at the Jet Propulsion Laboratory in Pasadena, California, a group charged with preparing to search for life in space, favors the sea theory. He says that as alkaline water seeped from certain types of vents, it would have mixed with ancient Earth’s acidic seawater, creating a tiny electrochemical charge that could have given rise to the first organisms. “Hydrothermal vents are great places to live,” Russell says.
That kind of scenario could also produce mineral pillars, where simple chemicals collected and concentrated in tiny holes. There, trapped together, they could link into the long chains necessary for biology. Then they would begin to form membranes, build systems that capture energy, and create a genetic code. Eventually these components assemble into a microbe that could leave a mark similar to the ones Papineau sees in his rocks.
A ridiculous idea, say the land theorists: The ocean is too watery for life to have gained its first foothold there. “It’s chemically implausible,” says Armen Mulkidjanian, a biophysicist at Osnabrück University in Germany. Martin Van Kranendonk, a geologist and astrobiologist at the University of New South Wales in Sydney, concurs with that assessment. “We regard the oceans as an extreme environment,” he says.
Van Kranendonk and others instead look to the surface of the new Earth, where briny hot springs, bubbling geysers, and rich gases would have served as the chemical cradle for life. Call it Volcano World. There, compounds of hydrogen cyanide and hydrogen sulfide could collect in freshwater pools. Cycles of wetting and drying, combined with searing UV radiation, could cause these chemicals to join up in a way that allowed them to self-replicate, eventually creating a genetic code. Researchers have shown in labs that the building blocks of DNA can arise this way. And Van Kranendonk’s own team recently discovered evidence of 3.5-billion-year-old life from a former hot spring in Australia.
The scientists who favor the sea theory counter that existence begins not with a code but with a meal. You need a metabolism and a source of energy before you can build anything like genes.
Besides, the chemicals involved are implausible (cyanide?). “That idea of life coming from organic molecules in the sunshine is ludicrous,” charges Russell. His jet-fueled analogy: You wouldn’t put a guidance system on a rocket with no engine and expect it to work. Fuel comes first.
In research, everyone is an expert. And no one is. Tackling the problem requires a whole university’s worth of scientists: physicists, biochemists, geologists, microbiologists, atmospheric scientists, and astrobiologists. Each entails different training and specialized knowledge. “Physics, van der Waals forces, the ideas Tolstoy can give me about self-organization—for the emergence of life, what don’t I need to know?” asks Russell.
Compounding the problem, there is no data from the moment of creation. The only source of information is the rocks, nearly as old as the planet itself, mostly twisted and deformed by heat, pressure, and time. No matter how sophisticated your tools, when you interpret ancient rocks, you’re in danger of getting Schopf-ed. “It’s a bit of a Wild West of geology,” says Nick Lane, an evolutionary biochemist at University College London who favors the deep-sea-vent theory. “It’s difficult to interpret. You risk getting egg on your face.”
After analyzing thin slices of a rock similar to this one (right), Dominic Papineau and Matthew Dodd concluded that they contained evidence of early life. If the researchers are right, the dark blob in the top-left close-up once sheltered bacteria. The tubes in the middle-left image, they believe, formed as the bacteria extruded waste. At bottom left, rings of white carbonate and dove-gray quartz form a hematite-flecked rosette—a shape that arises as biological materials rot, Papineau says. Photo courtesy of Dominic Papineau and Matthew Dodd.
Analyzing Ancient Clues
It takes just two steps to walk across Papineau’s small lab in the UCL nanotechnology building. From where I stand, it’s one step to the cabinet, filled with carefully labeled cloth bags of rocks he has collected from across the world. And it’s one step to the microscope he’s now hunched over. He is looking for something good to show me. He turns to a nearby computer and pulls up a micrograph, an image of the magnified insides of the rock that starred in the Nature report. To me, it looks like a kitchen countertop: black and white blobs, with spatters of dark red against a gray palette. To a trained eye (not mine), each color and shape reveals what the material is and how it got that way.
Geological sleuthing is a lot like conducting a criminal investigation. There never is a smoking gun because everything happened too long ago. The idea is to launch multiple lines of inquiry that let you explore your mystery from different angles. And just like when you’re corroborating witness accounts, if they all say the same thing, you can be reasonably sure your theory about what happened, when, and how is correct.
The first step in the forensic process required slicing off parts of the rock and milling them so thin that light could shine through. Then Papineau and Dodd began looking for graphitic carbon, which could be a sign that biological material had been present. They soon found it, in rosette formations the size of grains of salt.
On his computer screen, Papineau shows me the faint bull’s-eye mark. The center is pearly gray quartz with flecks of dark-red hematite. Rings of white and dove-gray surround it. “Look how beautiful this is,” he says. “It’s almost perfectly spherical.” This shape arises, he proposes, as biological materials rot, producing carbon dioxide that then forms carbonate minerals.
Next, Papineau pulls up a micrograph in which blood-red ribbons squiggle across a white-quartz background. He and Dodd hadn’t expected this, but in addition to chemical signs of life, they had also found what they believe to be actual fossils. These squiggles, or filamentous tubes, are similar to shapes made by modern iron-oxidizing bacteria in deep-ocean vent systems and are like much-younger fossils—an even more important clue. “You see this in the microscope, and you say”—he snaps his fingers—“this is telling me something, but I don’t know quite what.” He concluded that tiny, dark knobs in the formations are fossils, remnants of actual cells. The twisted ribbons are microbial waste products that had been coated in rusty-red hematite by geological processes.
To be certain of their case, Papineau and Dodd performed physical and chemical comparisons with far younger fossils and partnered with other researchers to test samples. Papineau had already analyzed the ratio of light to heavy carbon: Life prefers the lighter version, which he found in excess in this rock. He and Dodd used micro-Raman spectroscopy, firing a laser at the sample to study its composition from the spectra of scattered light. They aimed a focused ion-beam microscope on it to mill away nanoscale bits, looking at its mineral components. In each case, they found graphitic carbon, or minerals associated with it, and patterns that indicated life.
After they published their paper, the bubbling cauldrons of geology boiled over with supporters and detractors. Many praised the work without endorsing the conclusion: “Those authors did a really nice job of applying some advanced techniques,” says Ken Williford, director of the Astrobiogeochemistry Lab at Jet Propulsion Laboratory. “More will be required before we can be sure of the interpretation.”
The skepticism was equally swift. “Papineau strung together a whole bunch of possibilities that pointed to a probability, but we can’t make a leap to what the samples definitely are or aren’t,” says Van Kranendonk, who based his own 2017 finding on a different type of fossil pattern—sheetlike structures called stromatolites. Others cast doubt on the filaments and said they didn’t look right. The rocks had gone through too much heat and pressure to be trustworthy.
Papineau and Dodd say they have thought all this through. It’s true that any single phenomenon they saw could have been caused by nonbiological chemistry. But it’s extremely unlikely that every last one of the phenomena would have been present unless life too had once been present. “We always knew the work would be met with controversy, given the history of early-life claims,” Dodd says. “It’s not something trivial to claim.”
Rocky Ground: Papineau’s key sample came from this formation of hematite and magnetite. Photo courtesy of Dominic Papineau and Matthew Dodd.
An Earlier Timeline
It might not seem as explosive as the big-bang theory, or as disorienting as Darwin’s origin of the species, but the question of where and how life began is an enduring existential mystery. It points to our first beginnings, the stuff that we’re all made of—codes and chemicals. Papineau and Dodd might be right. Or not. But it looks likely that microbial creatures started swarming Earth almost as soon as it formed. Even without consensus on how and where life got going, everyone pretty much now agrees on a basic when: early. And quickly.
In fact, it could have happened more than once around the same time, in many places. “It’s entirely plausible,” says MIT geobiologist Tanja Bosak. That also means that it could have happened on another planet. In the case of Mars, our closest candidate, it could have come and gone.
NASA’s Mars 2020 mission will try to find that out. Engineers will outfit its rover with a micro-Raman spectrometer that can do a bit of what Papineau and Dodd did in the lab—analyze rocks for former biological content. Williford, who is the deputy project scientist for the mission, will use some of the Nuvvuagittuq samples to test the rover’s spectrometer during its development.
If a mission one day sniffs out former life in rocks on Mars or elsewhere, Papineau thinks it will shift our perception of our uniqueness in the cosmos. It might even “unify people,” he says. Van Kranendonk says it’d be like the Apollo astronauts looking back at our planet from space: “It could have a profound impact on our place in the cosmos.”
In the meantime, scientists will continue looking where they always have—in remote ancient rock, in biochem labs, in clean rooms under microscopes, and in bubbling vats like the one in Lane’s lab at University College London. It’s just a block away from Papineau’s office, but it’s a completely different world. Lane builds origins-of-life reactors to try to replicate the chemical reactions that lead to creation.
The first version, now retired, looks like something out of Breaking Bad: a big, smudged glass cylinder with a tube dangling from the bottom, partly encased in wrinkled tinfoil secured with masking tape. A thin bundle of wires snakes out below. When it’s switched on, hot hydrogen-rich alkaline fluid with common salts such as potassium phosphate and sodium sulfide seeps up the pipe into the chamber. It bubbles through acidic water rich in dissolved carbon dioxide, iron, and nickel, and starved of oxygen—like the seas were 4 billion years ago.
After a few hours, spidery black tubes form amid the alkaline and acid waters, mimicking early vent structures. One of Lane’s contraptions yielded formaldehyde, a precursor to complex biochemistry. He’s working on control experiments to verify that result. “A few people are taking this chemistry seriously,” he says. “I hope it’s only a matter of time before someone cracks it.”
Papineau and Dodd are still looking too. Among many other projects, they’ll send one of their rock-and-fossil samples to a synchrotron in France for 3D X-rays that could suggest which modern microbes are most closely related to their ancient microorganisms.
“Everything counts,” Papineau says. “These are the best-preserved microfossils we have. We have to seize that opportunity to characterize them as best we can.” In other words, these are among the finest ones we have now. But maybe one day, somebody will stumble across something better—older, clearer, more surprising.
If this field of research has proved anything, it’s that life takes any opportunity it can get, and it gets there in a hurry. Life happens.
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