Notes From an Environmentalist; The Comet Strike Theory that Just Wont die. Elegant theory upended by an ugly fact.
The Comet Strike Theory That Just Won’t Die
Mainstream science has done its best to debunk the notion, but a belief in a world-changing series of prehistoric impacts continues to gain momentum.
By Zach St. George
March 5, 2024
In 2007, a group of researchers, led by a nuclear physicist named Richard Firestone, announced an astonishing discovery. They had uncovered evidence, they said, that 12,900 years ago, a comet — or possibly a whole fleet of comets — struck Earth and changed the course of history. For the preceding two and a half million years, through the Pleistocene Epoch, the planet’s climate fluctuated between frozen stretches, called glacials, and warm interglacials. At that time, Earth was warming again, and the ice sheets that covered much of North America, Europe and Asia were in retreat. Mammoths, steppe bison, wild horses and other enormous mammals still wandered the Americas, pursued by bands of humans wielding spears with fluted stone blades. Suddenly, somewhere over the Upper Midwest — an explosion.
Presenting their claim in the Proceedings of the National Academy of Sciences, a top scientific journal, the researchers took the sober tone characteristic of such publications. But in “The Cycle of Cosmic Catastrophes,” a book published around the same time, two of the researchers described the scene more vividly. The impact caused the ground to shake and the sky to glow, they wrote. A hail of tiny molten particles sank into flesh and set forests ablaze. Soot blotted out the sun. Earth’s magnetic field wavered, and living things were bombarded by cosmic rays, confounding the navigational senses of turtles and porpoises, which beached themselves en masse. Addled birds plummeted from the sky.
Most disastrous of all, the impact shattered the ice dam holding back Lake Agassiz, a vast expanse of glacial meltwater that stretched across Manitoba, Ontario, Saskatchewan, Wisconsin and Minnesota. The lake cascaded into the Atlantic Ocean, where the freshwater pooled over the denser seawater, disrupting the convection current carrying warm water north from the tropics. The Northern Hemisphere plunged back into full-glacial cold.
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For decades, scientists had puzzled over the cause of this rapid climatic reversal, which they marked by, among other things, the reappearance in southerly fossil deposits of tundra plants. These included the wildflower Dryas integrifolia, which gives the 1,200-year time span its name: the Younger Dryas. Here was an explanation: The impact caused the sudden cooling, the Firestone team argued, and contributed to the demise of the mammoths, steppe bison and other large Pleistocene mammals, along with the people who pursued them.
Researchers later claimed that the Younger Dryas impact prompted a turn toward agriculture in Eurasia and eventually, civilization. It might even have influenced, in surprising ways, the outlines of our current nation-states. James Kennett, a member of the Firestone team, told me that if the impact had not led to the extinction of horses in the Americas, Native Americans surely would have domesticated them and would therefore have presented more formidable opposition to European conquistadors; perhaps they would even have been conquistadors themselves. “So the whole setup of human culture would have been very different,” he says.
Drawing out this counterfactual, we might imagine that the people of Europe came to speak a dialect of Lakota or Nahuatl or Yanomamo, that Siegfried and Roy performed with saber-toothed tigers and cave lions. Absent the climate-changing effects of agriculture and industry, the world might now be tipping back into an ice age. In short, without the Younger Dryas impact, nearly everything would be different. “Our modern way of life had its genesis,” according to the authors of “The Cycle of Cosmic Catastrophes,” “in the thunderous flash of crashing comets.”
This cometary origin story, with its mix of ancient humans, vanished megafauna and global cataclysm, quickly spread beyond the confines of scientific journals. Media outlets around the world covered the Younger Dryas impact hypothesis. It has been the subject of two more books and multiple documentaries, including one produced by PBS NOVA. Joe Rogan has discussed the hypothesis a dozen times on his podcast, and it provided the scientific underpinnings for Netflix’s 2022 hit series “Ancient Apocalypse.” But even as the hypothesis wormed its way into the public imagination, an important question persisted: Was any of it true?
Many geologists, astronomers, archaeologists, paleoecologists and other scientists with relevant expertise were immediately skeptical and soon published studies of their own rebutting the Firestone team, which responded with rebuttals to the rebuttals. While heated debate is typical in science, the back-and-forth quickly veered outside the usual bounds. Today some proponents of the impact hypothesis insist that skeptics make up a small but vocal minority desperately trying to prevent the inevitable acceptance of the hypothesis as fact. Others take a darker view, suggesting that the ongoing resistance to the hypothesis is a result of a coordinated coverup by the scientific mainstream. Still other observers hear in the stubborn persistence of the Younger Dryas impact hypothesis an echo of some unsettling trends in the public discourse: a tendency toward tribalism and distrust, the conspiratorial embrace of supposedly forbidden knowledge, the seeming triumphs of narrative over truth.
William Topping, an archaeologist, was studying a site on Michigan’s Upper Peninsula where ancient North Americans quarried the raw materials to make their stone tools, when he encountered a puzzle in the late 1990s: Anthropological and geological evidence indicated that the layer of soil containing the ancient artifacts dated to around 12,900 years ago, just before the start of the Younger Dryas. But radiocarbon dating suggested that the layer was only 2,900 years old. Topping sent an email about his problem to Richard Firestone, an expert on radioactive isotopes who was then working at the Lawrence Berkeley National Laboratory. Firestone, who told me that he has always had an interest in side projects, agreed to help.
Their investigation progressed slowly at first. Then, in the early 2000s, Firestone and Topping were joined by Allen West, who had recently left his career as a geophysical consultant to the oil and mining industries. “I was retired and bored,” West says, so he “decided to write a book.” A small asteroid had recently made headlines when it passed between Earth and the moon. His literary agent suggested he write a book about the hazard of asteroid impacts. After West came across an article that Firestone and Topping had published about their early research, he wrote to Firestone and proposed that they join forces.
The planet’s surface is a churn of deposition and erosion, uplift and subsidence, which tend to erase from sight evidence of even the most consequential events. The asteroid thought to have killed off the dinosaurs some 66 million years ago, for instance, remains apparent to us primarily as a thin, iridium-rich layer of rock found around the world and as a faint inscription on the edge of the Yucatán Peninsula, where it struck. Evidence of a much earlier collision between Earth and a Mars-size body, which scientists think hewed away the material that became the moon, is even more subtle, derived from orbital models and chemical comparisons of Earth rocks and moon rocks.
Firestone, Topping and West pursued a similarly faint set of proxies. They were particularly interested in metallic spheres — so-called microspherules, each a fraction of the width of a human hair — that Topping discovered in abundance at the Michigan quarry and other archaeological sites. Topping found few of these orbs below the soil layer with the errant radiocarbon dates, and few after. But the anomalous soil, a carbon-rich layer that other archaeologists called the black mat, was full of them. The trio suspected that the orbs were a result of an impact, which, they thought, could have also reset the radiocarbon dates at the quarry site.
West began traveling the country, visiting archaeological sites that dated to the beginning of the Younger Dryas. At many of the sites he visited, he found the same black mat, containing the same types of microspherules. He reached out to other experts, and some of them joined the effort. Ted Bunch, a retired NASA chief of exobiology and an expert on meteorites, was one. Another was James Kennett, who was based at the University of California, Santa Barbara, and who had helped found the scientific field of paleo-oceanography. In 2000, he was elected to the National Academy of Sciences, “one of the highest honors that a scientist can receive,” according to the academy’s website. Kennett had studied the Younger Dryas climatic reversal for decades and even mused upon the possibility that it resulted from a cosmic impact. When West approached him, Kennett says, “I grabbed onto this immediately.”
The growing team exerted a kind of gravity, drawing other scientists into the effort: archaeologists, impact specialists, chemists, geologists, a polar explorer. Each was adept at recognizing and interpreting different kinds of scientific proxies. Led by Firestone, West and Kennett, the group put together its hypothesis the way that contractors build a house, with masons, carpenters, plumbers, electricians and drywallers each playing distinct but complementary roles. A result was a hypothesis of sweeping scope but also one that, paradoxically, West notes, was beyond the full grasp of any single scientist.
By 2007, the team was ready to publish its work. In Proceedings of the National Academy of Sciences, Firestone, Topping, West, Kennett and 22 co-authors laid out the evidence from 25 sites scattered across North America. Along with the magnetic and carbon microspherules, they had discovered granules with unusual concentrations of iridium, bits of glasslike carbon containing “nanodiamonds” and “fullerenes with ET helium.” Together, these proxies were a clear indication of extraterrestrial impact, they argued. Each reached its highest concentration in the black mat, which in turn was consistently found to be 12,900 years old — the start of the Younger Dryas.
At a news conference that several members of the Younger Dryas impact-research team gave just before the journal released its study, Kennett seemed to anticipate some of the debate to come. “I think it’s going to be very hard for the skeptics — and there will be a lot of skeptics for this, as there should be, it’s a big discovery — that there was an impact of this proportion,” he said. “It’s going to be very hard for the skeptics to take this range of evidence.”
When the paper came out, Jacquelyn Gill was working on her dissertation at the University of Wisconsin, Madison, studying the Pleistocene mammal populations of the Upper Midwest through the proxies of ancient pollen, charcoal and fungal spores. The impact hypothesis almost perfectly overlapped with her research. “They’re talking about fire, they’re talking about vegetation, they’re talking about megafauna,” she says — all of it centered on the Great Lakes. But Gill, now a paleoecologist at the University of Maine, was dubious. The hypothesis depended on synchronicity, on all the various lines of evidence aligning perfectly 12,900 years ago and pointing to a sudden, disastrous event. Gill thought the Firestone team had significantly overstated this alignment, at least in regard to the impact’s purported ecological effects. In the lake cores from the Younger Dryas that she was studying, there was no abrupt spike in charcoal to suggest catastrophic fires. Pollen evidence indicated changes to the vegetation consistent with a quickly cooling climate, not an impact. The fossils of bones and the spores of dung-dwelling fungi each suggested that many large mammals were already in decline or even extinct thousands of years before the onset of the Younger Dryas; many others lingered long after. “None of this is lining up,” Gill says she thought.
Other scientists reached similar conclusions. One group of researchers reported that they couldn’t find the nanodiamonds described by the Firestone team. Another group discovered no signs of a continentwide fire that coincided with the beginning of the Younger Dryas — or even a unique degree of burning at that time. Yet another group announced that, after an extensive search for microspherules and other proxies, it was “unable to reproduce any result of the Firestone et al. study” and found “no support for Younger Dryas extraterrestrial impact.” A review paper published in February 2011 summed up these efforts: Outside scientists had been unable to reproduce seven of the Firestone team’s 12 original lines of evidence for an impact; the other five lines of evidence resulted from ordinary earthly geological processes. The article was titled — in what would turn out to be wishful thinking — “The Younger Dryas Impact Hypothesis: A Requiem.”
As they tried to replicate the Firestone team’s findings, the skeptics noticed numerous odd details that seemed to hover around the hypothesis. There was, for example, “The Cycle of Cosmic Catastrophes,” which came out just before the Proceedings of the National Academy of Sciences study. The book’s publisher was a division of Inner Traditions, which, according to its website, is “devoted exclusively to the subjects of spirituality, the occult, ancient mysteries, new science, holistic health and natural medicine.” The book, written by West and Firestone, intersperses a breathless account of their work with the “astonishingly similar stories” of floods and celestial conflagrations from dozens of ancient cultures, including the tale of the “Long-Tailed-Heavenly-Climbing-Star,” attributed to the Ojibwa. “It clearly wasn’t a science book,” says Jennifer Marlon, a paleoecologist at Yale who read the book soon after seeing the PNAS study. “I just thought, Well, this is kind of silly.”
In 2011, an article by Rex Dalton in the magazine Pacific Standard revealed the strangest detail yet. Shortly before West first reached out to Firestone, he was convicted in California, under his given name, Allen Whitt, “for masquerading as a state-licensed geologist” while conducting groundwater surveys across the state. Not long before that, Dalton reported, a “new age” business that West owned in Sedona went under, and his geosciences business went bankrupt.
When Mark Boslough learned about West’s past — first revealed publicly in the Pacific Standard article, titled “Comet Theory Comes Crashing to Earth” — he says it “was kind of when a lightbulb went on over my head.” Boslough, an impact physicist at Los Alamos National Laboratory, helped pioneer the study of cosmic airbursts — meteors that explode in the atmosphere instead of striking the planet’s surface. He was skeptical of the Firestone team’s hypothesis from the beginning, but he says that he viewed them as essentially ordinary, if misguided, scientists. “Until that point, I took their evidence at face value,” he says. “I never believed that again.” To Boslough, West’s background was a sign of rot at the center of the impact hypothesis. He expected that West’s colleagues would abandon both him and the hypothesis, he says. “And the opposite happens.”
“The Cycle of Cosmic Catastrophes” “was never intended to be a scientific book,” Allen West says. “It’s strictly a popular attempt to talk about impacts.” The “new age” business was in fact a self-help organization, he told me. And his fraud conviction was really more of a bureaucratic mix-up, he says, resulting from his mistakenly failing to fill out the proper forms. Indeed, not long before Dalton’s article was published, a judge revised West’s verdict to “not guilty” and expunged the conviction from his record.
West suggests that the failure of many scientists to replicate the Firestone team’s results was because of a lack of understanding, improper methodology, obstinacy or even jealousy. He points to the long history of groundbreaking scientific hypotheses meeting with initial resistance. Galileo was committed to house arrest for his public backing of heliocentricity. Darwin was engulfed in controversy after he proposed evolution by natural selection. Alfred Wegener was ridiculed in the early 1900s when he suggested that continents drift. “That doesn’t mean that everything that scientists object to is true,” West says, “but it does mean that that’s the typical response to something new.”
Some of Firestone and West’s co-authors did distance themselves from the effort, but other scientists took their places. In 2016, West and several colleagues formed Comet Research Group Inc., which, according to its website, “cooperates with and provides funding for selected impact research scientists around the world.” The organization is a division of Rising Light Group, an Arizona-based nonprofit that “promotes public awareness and tolerance in a variety of fields, including religion, philosophy and science.” To skeptics of the impact hypothesis, this affiliation was another sign that something was amiss. But West, listed as a director of Rising Light Group, dismisses any suggestion that religion or mysticism has seeped into the scientific research on the Younger Dryas impact hypothesis. “We have scientists in our group of all kinds of religious persuasions, and to my knowledge, none of their beliefs have gotten into our papers,” he says. “Any scientist who judges the beliefs of a scientist outside of that paper, to me, that’s not good science.”
Joined by a growing cohort of collaborators, the Comet Research Group churned out new research, presenting such evidence as shock-synthesized hexoganal nanodiamonds from Santa Rosa Island, Calif.; siliceous scoria-like objects from Melrose, Pa., Blackville, S.C., and Abu Hureyra, Syria, as well as corundum, mullite, sessile and lechatelierite; elevated levels of chromium, iridium, copper, nickel and ruthenium in the sediments of western Russia’s Lake Medvedeskoye; planar deformation features, orthoclase and monazite in the northwestern Venezuelan Andes; and suggestive patterns in the eubacterial and paleosol chronosequences in the Mount Viso catchment of the Cottian Alps. What Topping and Firestone first uncovered at a single archaeological site in Michigan had expanded into, as one researcher put it, a “global cosmic catastrophe.”
These elements, minerals and geological forms are real. What many outside scientists continued to dispute was the hypothesizers’ interpretations of what these things meant. To the nonscientist, this back-and-forth is impenetrable. “It is very difficult for laypeople to assess whether something is true or not,” says Tiffany Morriseau, a social cognitive scientist at the University Paris Cité. She was part of an interdisciplinary team of experts commissioned by the European Union in the wake of the pandemic to investigate the decline of trust in experts. The group thought that, in a complicated world, there is no choice but to rely on experts. After all, everyone is a layperson in some facets of their existence. The plumber must at times place trust in the veterinarian, who at times relies on the engineer.
Looking to experts is one way that people employ what psychologists call “epistemic vigilance” — a kind of immune system for our individual conceptions of reality, allowing us to parse truth and falsehood. But this defense can be confounded in cases of contested expertise, with rows of Ph.D.s arrayed on each side, offering conflicting accounts. In such a situation, Morriseau says, a person might be tipped toward one understanding over another by how closely it aligns with previously held beliefs or political or cultural affiliations. A compelling story might make the difference.
In a recent paper, two psychologists at the University of California, Santa Barbara, Spencer Mermelstein and Tamsin German, have argued that pseudoscientific beliefs, which range from the relatively harmless (astrology, dowsing) to the deeply malignant (eugenics, Holocaust denial), tend to find cultural success when they hit a sweet spot of strangeness: too outlandish, and the epistemological immune system will reject it; too banal, and no one passes it on. What is most likely to take hold, Mermelstein says, is something that adds an intriguing twist to a person’s current sense of the world. The idea that a comet impact shaped many details of the modern world is not just surprising and interesting, he says; it also roughly fits most people’s previous understanding of Earth’s geologic past. And it’s simpler and more satisfying than alternative explanations for the events of the Younger Dryas. “It’s just like, one big cause, one big outcome,” Mermelstein says. “We can move on, right?”