Joe Zadeh is a contributing writer for Noema based in Newcastle.
Seasoned bioethicist Laurie Zoloth has a trick she likes to play in her seminars at the University of Chicago. She tells each student to pick up a pencil, then she gives them a series of instructions about how to maneuver it in their hands. At some point, nearly everyone drops the pencil. And that’s the point she’s trying to illuminate: “Humans always make errors,” Zoloth told me over Zoom. We drop things, we forget to switch things off, we lose our focus, we get tired. “Being human is like driving in a snowstorm, all the time,” she said, the hint of a smile emanating from beneath her round glasses.
I was interviewing Zoloth about events that had taken place a year earlier, in late 2024, when she virtually attended the monthly meeting of the Engineering Biology Research Consortium security committee, where synthetic biology professionals from academia, industry and government meet and discuss security implications in the field.
John Glass was also on the call. Glass is one of the most prominent biologists in the U.S. and the leader of the Synthetic Biology Group at the J. Craig Venter Institute (JCVI). “I’d never seen him really worried about stuff before — he’s always smiling,” Zoloth told me. On this particular day, however, no smiles. Nobody was allowed to share publicly what Glass was about to tell them. It was embargoed for another few weeks. And then he began to explain what, for some time, had mostly been discussed privately in small meetings between increasingly concerned scientists.
“I was horrified,” said Zoloth.
A few weeks later, on Dec. 12, 2024, what Glass had spoken about that day became public knowledge. A group of 38 prominent scientists from around the world — including 16 members of national academies and two Nobel Laureates — called for a halt on the creation of of a novel synthetic bacteria that, if realized and accidentally leaked into the environment, could dodge typical ecological checks and lead to an uncontrollable spread of deadly infection that posed a threat not just to humans but to many forms of life upon our earth and in our oceans, from the animal to the vegetal, from the micro to the macro. They provided a robust 299-page technical report to legitimize their worries.
The organism of concern is an artificially created mirror-image form of bacteria, known popularly as mirror life. For decades, biologists have been trying to imitate what, so far, only nature has been able to do: build a living self-replicating cell from scratch. And many believe they are getting closer. But the work to create mirror life, while adjacent to this field, is different, stranger. Mirror life would be the genesis of an organism that does not imitate nature but contradicts it. It would have a molecular structure opposite to that of all existing life on Earth. It would be something completely new under the sun, and its creation would commence the beginning of a second tree of life.
The road to hell is paved with good intentions. The initial interest in creating mirror biology promised wonderful things: never-before-seen drugs, entirely new biomaterials and profound answers to the origins of life. The U.S. National Science Foundation, the National Natural Science Foundation of China and the European Commission all supported work in this direction. But in recent years, many of the biologists working on its development have come to realize the potential worst-case-scenario consequences of their work. A mirrored organism would be essentially invisible to the immune systems of humans, animals and plants, bypassing the biological defenses that we and other living beings have evolved. Many natural predators, viruses and diseases would be unable to recognize it and therefore powerless to limit its reproduction. As Ariel Lindner, research director of the Systems Engineering and Evolution Dynamics Unit at the French National Institute of Health and Medical Research, or Inserm, told me in an interview: “Living systems know how to deal with invaders, but not with space invaders. Mirror life is a kind of space invader.”
“I think it takes a moment to understand what we are talking about here,” Sebastian Oehm, an adjunct assistant professor at the JCVI and CEO and founder of synthetic biology company SynX Therapeutics, told me over Zoom. He is also one of the report’s authors. “This would be in the environment basically forever, because there is no real way to get rid of it. In our report, we settled on the words ‘unprecedented risk,’ but that is maybe too weak. There is really nothing else like it. It is its own class of danger.” Unlike in Zoloth’s classroom, there would be no picking up the pencil and trying again.
“For decades, biologists have been trying to imitate what, so far, only nature has been able to do: build a living self-replicating cell from scratch.”
Once evangelists have become prophets of doom, bellowing warnings. “Scientists usually wait until something happens before we act on it,” said Kate Adamala, a biochemist at the University of Minnesota, and one of the scientists who originally worked on the development of mirror life. “If we wait for this, it will already be too late.”
Despite the alarm, it’s important to state: Mirror life does not exist. In fact, there are substantial technical buffers to overcome before it becomes even remotely possible. Most experts estimate we’re between a decade and three decades away, although George Church, pioneer of modern genomics and professor at Harvard Medical School and MIT, told Harvard Magazine, “it’s already gotten to the point where somebody who is sufficiently mischievous could start with what we’ve already published and run with it.” The technical report warns that if no serious concerns are raised now, the default course of well-intentioned scientific and technological development would likely result in its eventual creation. “I can see a future drug company saying: ‘We’re going to build mirror life that is completely safe, because we’ll make sure it can’t run amok, and trust us, we’ll keep this bio-contained,’” Glass told me over Zoom. “Perfect biocontainment is a myth.”
The technical report was published alongside an article in the journal Science. A story landed that very day in The New York Times and was featured in print on Dec. 17, 2024, with the headline, “A ‘Second Tree of Life’ Could Wreak Havoc,” followed by an in-depth explanation from science journalist Carl Zimmer. The Guardian ran a similar article. In the scientific community, a flurry of trepidation and excitement ensued as the report’s authors implored fellow scientists to scrutinize and poke holes in their work. “We thought there might be an error, which would have been great for the world, and we had nothing to worry about. Unfortunately, this hasn’t happened,” Oehm said. By April 2025, 96 experts from more than 20 countries had endorsed an entreaty calling for governance mechanisms to prevent the creation of mirror life.
But in the wider public arena, something rather unexpected happened. Despite its potentially monumental proportions, the story just didn’t go anywhere. “It was shocking to me when nobody really noticed it, when it didn’t stop the world,” Zoloth told me. “I felt like it spoke to how chaotic our lives have become. I expected a public outcry — there wasn’t. Maybe it’s too big to deal with? Perhaps it’s because of Covid-19, which was also going to be the end of the world — and the world, in an important way, did end for millions of people — and yet we’re carrying on as if it didn’t happen. It really feels like the pandemic didn’t happen. Fish returned to the canals of Venice, bears and wild turkeys wandered through cities. It all feels like a fairytale now,” she said, then paused. “But the trouble with mirror life is that it is so much worse. This isn’t just tinkering with DNA; it’s unwinding the whole structure of the world.”
Louis Pasteur was short-sighted, suffering from a myopia induced by elongated eyeballs. As a result, he liked to place his face very close to his work. One story tells of him dropping onto all fours in a pasture to observe the wriggling of an earthworm, a suspected carrier of Bacillus anthracis. This French genius of 19th-century science gave us fermentation, germ theory, immunization and medical hygiene. He vanquished the notion of spontaneous generation and put an end to any lingering hangovers in Western medicine about diseases caused by spirits and devils. But like one might imagine a genius, he was, according to his biographer Patrice Debré, a solitary, secretive, authoritarian, sometimes unfair, haughty, arrogant and demanding man, who made every effort to build his own fame. And yet, despite his lifelong self-aggrandizement, arguably his most profound achievement remains perhaps his least famous. To understand mirror life, one must understand what Pasteur saw through his microscope in the late 1840s.
Pasteur was then in his late 20s and working as an assistant chemist in the laboratory of Antoine-Jérôme Balard at École Normale Supérieure, in the 5th arrondissement of Paris. He would spend hours in silent observation, his grayish-green eyes glued to the microscope. Collaborators said it was as if Pasteur was in a trance when he worked. His myopia seemed to so enhance his close vision that, they said, in an object under the microscope or between his hands, he could see things that were hidden to normally sighted people around him.
“A mirrored organism would be essentially invisible to the immune systems of humans, animals and plants.”
At the time, his obsession was crystallography, the study of the structure of crystals — their perfectly ordered shapes seemed to offer clues about the hidden structure of matter. Nineteenth-century crystallographers used polarimeters to shine polarized light through crystalline forms to study how their internal structure affected their passage. Some crystalline solutions caused polarized light beams to deviate in different directions, while others had no effect at all.
One particular mystery had been obsessing chemists across Europe. It concerned the crystals being found in the sediments of fermenting wine. Tartaric acid crystals, or “wine diamonds,” were a familiar and expected deposit during the vinification process, but chemists had begun to notice a second substance appearing alongside them. These mysterious crystals looked just like tartaric acid. In fact, the two substances were doppelgängers — twins in every way, in chemical composition, in weight and, supposedly, in structure. And yet when polarized light was shone through their solutions, tartaric acid deviated the beam, while the unknown substance did nothing. Something was amiss, something beyond normal observation. “How could one conceive of two substances that resembled each other so much without being identical?” Pasteur recalled years later. A lot was at stake here: If two chemicals could be identical in every way but display some ineffable difference in their properties, then the chemist’s conception of the world — how they defined and categorized chemicals — was on the verge of collapse. This problem, wrote Pasteur, “preoccupied me a good deal … [and] upset all my ideas.”
Peering down the microscope at the unknown substance, he examined its molecules, one by one, measuring their contours with his goniometer. In the lab that day, the young and inexperienced Pasteur noticed something that several eminent scientists before him had failed to see. Experts like Joseph Gal have attributed this moment to Pasteur’s vivid visual imagination honed during an artistic youth spent making lithograph portraits of family and neighbors — in lithography, the final image on paper is the mirror image of the original etching on limestone.
All the molecules were asymmetrical, but some had facets and contours that leaned to the left, while others leaned to the right. There were two types of molecules present in this substance, yet they were mirror images of one another — like a face staring at its reflection — identical except for the inverted orientation of their features.
Pasteur, usually quite reserved, began shaking uncontrollably. He couldn’t bear to look at his polarimeter, perhaps out of fear that what he’d just seen with his own eyes may not have been so. As legend has it, he rushed into the corridors of École Normale Supérieure, embraced his mentor, Jean-Baptiste Biot, and dragged him to Jardin du Luxembourg to explain what he’d witnessed. Pasteur had discovered that the same chemical molecule can exist in two mirror-image forms, which would come to be known as right-handed and left-handed. These molecules are twins in almost every way except for their orientation in space, much like your hands, eyes, ears and feet. In nature, only right-handed tartaric acid ordinarily existed — most notably in grapes, bananas, tamarinds and other fruits — but some quirk of the industrial process had synthesized a substance that was an equal mixture of both right-handed and left-handed forms.
It was revolutionary work; the first time geometry had been used to study a biomolecule in three-dimensional space. To explain it to his fellow scientists, he carved large cork models of both left-handed and right-handed tartaric acid crystals, reproducing their edges and facets in great detail.
Pasteur became fascinated by this phenomenon of molecular asymmetry. What had provoked nature into creating these strange mirror-image forms? “I am on the verge of mysteries, and the veil which covers them is getting thinner and thinner. The night seems to me too long,” he wrote to his friend, Charles Chappuis, in 1851. He began making a study of every molecule he could get his hands on, rummaging through the cupboards of science departments, in a desperate bid to begin organizing the molecular world into categories of symmetrical and asymmetrical.
As he meticulously examined each sample, an odd finding began to emerge. Almost all the samples he examined that originated from animal or plant matter — essential oils, gums, cellulose, gelatine, fibrin and albumin — were composed of asymmetrical molecules. They were either right-handed or left-handed, but they were always asymmetrical. In contrast, the samples of mineral origin — gypsum, chalk, garnet, pyrite and others — were composed exclusively of symmetrical molecules. In other words, symmetry could be a key distinction between the molecular world of living and nonliving matter. Life, it appeared to him, requires asymmetry; it must be oriented in one direction or another.
“Living systems know how to deal with invaders, but not with space invaders. Mirror life is a kind of space invader.”
But why did nature sometimes choose left over right and right over left, if both are possible? The true profundity of what he was uncovering began to overwhelm him. In correspondence, Pasteur confided to his close friend, Dr. Godélier: “I am really afraid that this time I have taken on the impossible. I want to track down the cause of one of nature’s greatest mysteries, whose unraveling, it seems to me, would have the most far-reaching consequences.” He began referring to the phenomenon in near spiritual terms, as some sort of unknown force, something “cosmic.” “I am inclined to believe that life as it is manifested to us must be a function of the asymmetry of the universe or of the consequences of this fact,” he once said.
What if, he pondered, we could pursue biology through the looking glass and create biomolecules that reversed nature’s decisions? What if we could turn left-handed biomolecules into right-handed biomolecules and vice versa? With this power, we would gain access to an entirely unknown world of substances and reactions that would lead not only to the transformation of species but also toward, in Pasteur’s words, “the creation of new species.”
He embarked on a series of bizarre experiments, hoping to uncover that magnetism was somehow responsible for this phenomenon. To test it, he acquired a number of incredibly powerful magnets and grew crystals under the influence of their force, hoping it would cause some effect. The molecules remained unchanged. He also conducted experiments to transform vegetal life into its mirror-image form. Perhaps, he wondered, the passage of the sun through the sky from east to west might be exerting the cosmic asymmetric force? He arranged a motor-driven mirror to redirect sunlight, essentially creating a miniature artificial world in which the sun rose in the west and set in the east. Here, he grew plants in the hope that this mirrored sunlight would somehow reverse their handedness at a molecular level. It didn’t.
Pasteur’s peers begged him to stop. “I wish I could turn you away from your idea of trying to study the influence of magnetism on vegetation,” wrote Biot. “You have too much to do to run from the certain to the uncertain.” In a letter to his father, Pasteur himself realized he had become trapped by his own curiosity. “My investigations are going rather badly,” he wrote in December 1853. “One must be a little mad to take on what I have taken on.” Perhaps Pasteur had become intellectually frustrated, perhaps he feared for his sanity, or perhaps he felt he may have been shining a light on some aspect of knowledge that should remain in darkness, but the following year, he abruptly halted this line of inquiry and moved to Lille to become a chemistry professor and dean at the university. There, he turned his attention to beet root alcohol and the mysteries of fermentation, all of which would lead to the invention of pasteurization.
Pasteur’s grandson, Louis Pasteur Vallery-Radot, recalled a memory of his grandfather during the final years of his life. He observed him at his desk writing quietly, looking serious and sad, his grandfather’s left side now partly paralyzed by a stroke he had at the age of 46. Pasteur stood up and turned to his grandson: “Ah, my boy, I wish I had a new life before me! With how much joy I should like to undertake again my studies on crystals!”
Fantasies about the reflected image run deep in our psyche, ever since Narcissus bent over the spring. The mirror’s eerie quality was deeply mined by Lewis Carroll in Alice’s Adventures in Wonderland. As Alice told her cat, when she peered into the mirror above the parlor mantel at Looking-glass House, everything in the room seemed to “go the other way.” It has also intrigued some of the most influential figures in Western philosophy. “What can be more like my hand or my ear, and more equal in all points, than its image in the mirror? And yet I cannot put such a hand as is seen in the mirror in the place of its original: for if the original was a right hand, the hand in the mirror is a left hand, and the image of a right ear is a left ear, which could never serve as a substitute for the other,” wrote Immanuel Kant in “Prolegomena to Any Future Metaphysics.”
“This isn’t just tinkering with DNA; it’s unwinding the whole structure of the world.”
In mathematics and sciences, this mirror-image phenomenon is known as chirality. It comes from the Greek “kheir” meaning hand, and was coined by Lord Kelvin in 1883, some 34 years after Pasteur’s initial molecular odyssey. Something is chiral, Thomson explained in a lecture at the Oxford University Junior Scientific Club, “if its image in a plane mirror, ideally realized, cannot be brought to coincide with itself.” The threads of common screws, the twisting shells of snails, the spiral staircase, the tendrils of climbing plants — these are all visible everyday examples of chirality in action, coiling in a particular left or right-handed way, most of the time. Honeysuckle almost always twines clockwise, while bindweed almost always twines counterclockwise. When the two meet, they become twisted in a delicate embrace. “The blue bindweed,” poet Ben Jonson presented to a royal court in 1617, “doth itself enfold with honeysuckle.”
The jury is still out on whether Pasteur was right about magnetism and mirrored suns, but his fundamental assumption that chirality is somehow integral to life has proven true. We now know that things far beyond the reach of his 19th-century microscope still pertain to his hypothesis. The double helix strands of DNA — first mapped by James Watson, Francis Crick, Rosalind Franklin and Maurice Wilkins around 58 years after Pasteur’s death — and RNA both coil to the right and are composed of right-handed sugar molecules, whereas amino acids and proteins are almost exclusively left-handed. “Everything from the simplest bacteria and fungi to the most complex plants and animals uses left-handed proteins and right-handed DNA,” biochemist Michael Kay, at The University of Utah, wrote in the magazine Undark in January 2025.
This is not just a quirk of exquisite natural beauty; it’s one of the key factors in determining whether certain molecules can or cannot interact. Chirality enables the precisely choreographed dance of almost all the natural chemical activity on Earth, in which certain keys open certain locks. “Almost every process in biology is based on chirality,” said Oehm. The left-handed protein doth itself enfold with right-handed sugar. And nature’s choosing of either left over right or right over left in various biological circumstances remains a great mystery, a glorious reminder that humanity lives on an incomprehensible planet. For good reason, the author Martin Gardner once described our handed cosmos as “the ambidextrous universe.”
Scientists have long been drawn toward the untapped potential of what might lurk down the passages nature chose not to take. Mirror biology is the study and practice of synthesizing biomolecules with the opposite handedness of their naturally occurring counterparts. These mirrored forms can have surprising, Carollesque effects. Right-handed carvone smells like spearmint, whereas its left-handed version smells like caraway. The right-handed version of asparagine — the amino acid found in asparagus — is tasteless to bitter, whereas the left-handed version tastes sweet. Sometimes these effects can be dangerously unpredictable. Thalidomide was widely marketed and sold in Europe, Australia and some South American countries primarily as a treatment for morning sickness in the late 1950s and 1960s, but it contained both the active molecule (which did indeed treat morning sickness) and its mirror version (which was highly teratogenic), leading to more than 10,000 infants being born with malformations.
For scientists, the therapeutic benefits of exploring these chemical mirror worlds are myriad. When we take medicine, our bodies treat it as a foreign substance — enzymes immediately begin breaking it down through a process called drug metabolism. This limits how long a medicine remains active, often requiring further doses to maintain a therapeutic effect. But medicines made from mirror molecules operate largely outside of nature’s system of locks and keys, beyond our body’s normal surveillance and clearance mechanisms. “They can be very stable, because all the enzymes in the body that would normally break them down can’t act on them.”
The ambition for mirror biology is to create drugs that remain active longer, potentially at lower doses — and with fewer of the side effects that come from the body’s attempts to process and eliminate them. To this end, numerous mirror-image peptides, DNA and RNA molecules are being developed for a range of diseases, from cancer to inflammatory disorders. There are mirror-image enzymes capable of degrading many common plastics, without succumbing quickly to general biodegradation themselves. Scientists are also investigating whether mirror DNA could be the future of information storage, a near-imperishable place to put the scarcely imaginable amounts of data we now produce each year.
“Life, it appeared to [Pasteur], requires asymmetry; it must be oriented in one direction or another.”
It was the promise of projects like these, as well as many other adjacent avenues of synthetic biology research, that led scientists to wonder whether they could use these mirror biomolecules to assemble a radically new form of life. “The creation of mirror-image life is one of the ultimate applications of synthetic mirror-image proteins,” Richard Payne, a chemist at the University of Sydney in Australia and his colleagues wrote in the journal Nature Reviews Chemistry in 2023. Why exactly would we create mirror life, I asked Oehm. “When you consider the academic interest in this, I think you first have to remember: it would just be quite wild. You and I, as well as the monkey, the tree, the mouse, and the bacterium, we all have the same ancestor: LUCA, the last universal common ancestor. But if you created mirror life, that wouldn’t be LUCA anymore.”
Theoretically, scientists could take one of the simplest forms of life, bacteria, choose a particularly well-understood type, say E. coli, and — with enough money, time and a few more scientific breakthroughs — create a synthetic version that flips the structures of its natural molecular components to their mirror images. After all, if it works one way, it should work the other — left-handed scissors work just as well as right-handed scissors. An oft-quoted phrase in the world of synthetic biology is the theoretical physicist Richard Feynman’s: “What I cannot build, I cannot understand.” Adamala added, “That was the motivation: if we could make a mirror cell, then we could make anything. We would really understand every single step that is required to make life.”
In 2019, a team of biologists that included Adamala was awarded collaborative research grants totaling around $4 million to pursue the dream of creating mirror life. It wasn’t until around 2024 that they became aware of the warning lights flashing in their peripheral vision: That the very qualities that made mirror molecules so endlessly useful — their ability to float through the world less likely to be detected and resistant to degradation — could also make mirror life so cataclysmic.
“It wasn’t like someone came to me and said: ‘You must not do it, because it will kill everyone.’ It was very gradual,” Adamala told me.
Last October, I traveled to Paris to attend the International Genetically Engineered Machine (iGEM) competition’s Grand Jamboree. The Grand Jamboree is a world expo of synthetic biology that has become the epicenter of this fast-growing $19.75-billion global industry. Synthetic biology is as much a worldview as it is a field. It involves blurring the line between biology and technology: Rather than studying how nature is, it focuses on manipulating, engineering or redesigning nature to achieve whatever we wish it to do. This is symbolized by the iGEM logo: a biological cell entwined with a cogwheel. Over the expo’s four days, some 5,000 people from around the world visit to see the cutting-edge advancements that genetic engineering promises to bring in the future.
When I arrived on the fourth floor of Pavilion 7 at the Paris Convention Centre — around 3.5 miles from where Pasteur discovered molecular chirality — the mood in the air was jovial and upbeat. The conference mascot, a green googly-eyed microbe, welcomed arriving visitors, posing for photos and dancing to the music being pumped from speakers, which, at the time of my passing, was “Voulez Vous” by ABBA. The expo space had been divided into quaint villages with less quaint names: Infectious Diseases Village, Climate Crisis Village and Oncology Village, to name a few. Each contained 10-20 stalls, where teams from universities across the globe pitched their research to anyone who would listen. It had the feeling of a bustling indoor market, except the goods being sold were radical cures for hemorrhoids, new methods for detecting breast cancer, and “snaccine” (edible vaccines).
A CEO on the main stage shared his story of engineering petunias to glow like jellyfish. “What problem are we solving?” he said to the audience. “In the normal sense of that question, we aren’t.” In the chill-out area, named “Protein Park,” young scientists played table tennis and foosball, while others mused over chessboards or queued for waffles at the waffle stand. One group wore Deely boppers on their heads, atop which the twisted ladder structures of DNA wobbled on springs. For some, the occasion, and no doubt the flights to get here, were too much: Toward the end of each day, I found the occasional young boffin resting their weary head on a table or sleeping directly on the floor beside their stall, nestled in a pile of coats and rucksacks. Amid this festival atmosphere, it was hard to reconcile the fact that this was the same industry that had launched such a chilling warning of apocalypse to the public 10 months prior.
“Chirality enables the precisely choreographed dance of almost all the natural chemical activity on Earth, in which certain keys open certain locks.”
On day two of the event, I attended the only talk at iGEM scheduled to address mirror life. The panel consisted of six scientists, including Adamala. To begin, the panel chair ran a quick interactive poll of the audience to gauge their knowledge of the topic. The majority had only heard the term “mirror life” briefly or not at all, while around a third said they had read about it extensively. I’d expected higher awareness. Adamala went first, sketching the potential dangers.
She told the audience to have in mind the old folktale of the tortoise that wins the race against the hare, crawling slowly and steadily. “[Mirror life] wouldn’t be the fastest or most fit organism out there, but it would just keep making copies of itself uncontrolled. And that would be,” she paused, “bad.” I had posed the question of what this “bad” would look like if the wider world came into contact with this thing, this double, this replicating reflection to each of the scientists I spoke with for this story, but a clear overall picture of how an outbreak would proceed was difficult to parse. After all, we were dealing in complex hypotheticals about an organism that doesn’t exist, and every one of them was careful to preface any projections with statements to the effect of, “Ultimately, we don’t know.”
Firstly, what would mirror life sustain itself on? Would it not be a little like a fish in the desert, marooned in a world of opposite chirality, and therefore, food it cannot eat? Yes, said Oehm, however, he told me, there are sufficient quantities of achiral nutrients it could consume. Glycerol, for example, is an achiral nutrient found in the bodies of humans, animals and plants, as well as in the environment. “It would be enough to support mirror bacterial growth outside the lab,” he said. Mirror bacteria would grow more slowly than natural bacteria because food would be less abundant. However, its lack of natural predators would mean it would replicate faster than it dies. “That’s still exponential growth; even if the doubling times are lower, the result could be large mirror bacterial populations,” said Oehm.
The absence of predators is a key, yet contentious, issue. Bacteriophages — commonly known as phages, from Ancient Greek phagein meaning ‘to devour’ — are viruses that infect and destroy bacteria, and are the best in the world at their job. They are incredibly diverse and ubiquitous, found in practically everything from water to dirt, from Arctic ice cores to hot springs, as well as in your gut, skin and lungs. In one teaspoon of seawater, there are five times as many phages as there are people in Rio De Janeiro, Nicola Twilley wrote in The New Yorker in 2015. In nature, bacteria and phages wage a never-ending battle. But, say many scientists, all of the weapons that phages have evolved for this war will be ineffective against mirror life.
The same applies to other predators of bacteria, like worms and plankton. “They could ingest mirror bacteria, but they couldn’t necessarily break it down. They would be eating but not consuming. And we don’t know if that would kill them,” said Glass when I spoke to him over Zoom. With reduced competition, Adamala told me it is possible to imagine that mirror life would eventually become the dominant bacteria in oceans and soils. “Crop yields would go down; the productivity of rainforests and other ecosystems would go down. And then you would have a direct effect on food production, animal life, and climate,” she added.
It would likely proliferate in the bodies of anything with an immune system: plants, insects, animals, us. Our bloodstream, Adamala told the audience at iGEM, would be like a warm little pond where it could grow, unhampered by our immune systems. And it doesn’t necessarily need to be toxic for it to be deadly. Multiplying inside our bodies, it could simply take up space. When I spoke to Glass, he compared it to the thick, sticky mucus that lines the respiratory epithelium of patients with cystic fibrosis. “They suffocate — not because the mucus is particularly toxic, but because it eliminates the capacity of their lungs to get oxygen into their bloodstream.”
Surely, I asked Vaughn Cooper — an evolutionary microbiologist at the University of Pittsburgh and one of the co-authors of the report — when we spoke over Zoom, it would evolve to specialize on particular hosts rather than infect every living thing.
“The ambition for mirror biology is to create drugs that remain active longer, potentially at lower doses — and with fewer of the side effects that come from the body’s attempts to process and eliminate them.”
“It will evolve to focus on all,” he replied. “Every species would be equally foreign and, in some sense, equally susceptible. Sure, there are physical barriers — trees are not as easy to knock a hole in as nematodes — but once the mirror bacteria is inside, it’s all the same to them.”
One thing every author of the report I spoke to seemed to agree on was that this newly minted mirror life would be unstoppable. “Once it’s out, it’s out for good,” said Cooper, who seemed genuinely distressed at the thought. “There’s no way you could provide defenses against such a thing to all susceptible life forms at once — you can’t bleach the earth … That’s why prevention is far better than countermeasures … There is a lot we don’t know, and we could still be wrong. But do you really want to risk it?”
Many of the world’s biggest international bodies are taking the threat of mirror life seriously. In March, the United Nations Secretary-General’s Scientific Advisory Board called for the scientific community to define clear red lines, strengthen safety and monitoring practices, and establish responsible policy well before it becomes feasible. The United Nations Educational, Scientific and Cultural Organization (UNESCO) and its World Health Organization have also acknowledged the urgency of the issue, with the former recommending a precautionary global moratorium. In September, many of the scientists I interviewed for this story are expected to gather in Singapore for the next major mirror life conference to discuss what these red lines and responsible policies may look like.
Filippa Lentzos, an associate professor in science and international security at King’s College London, will be in attendance. She thought it was good news that most scientists agreed, but she told me, “to actually implement a halt to mirror life research, you need something with teeth.” Like a plant needs light and water, 21st-century science requires funders and publishers to survive: someone to pay for research and somewhere to publish it. That’s why, she said, the focus of the mirror life discussion now needs to switch from the scientists themselves to the major funders and academic publishers. “They are the real levers of scientific careers, and therefore uniquely positioned to be gatekeepers of the rules,” said Lentzos. Stop funding and publishing anything that contributes to the development of mirror life, and you stop its progress. “At least, legitimate progress,” she added, cautiously.
A globally agreed-upon moratorium on mirror life research wouldn’t necessarily be a bulletproof solution. A moratorium isn’t forever; the word comes from the Latin “morātōrius,” meaning “delaying.” They are normally subject to reappraisal once certain conditions are met that deem it safe to proceed. In 2017, the U.S. National Institutes of Health lifted a ban on controversial experiments involving organisms with pandemic potential, such as influenza and coronaviruses, that had been in place for three years. Moratoriums also aren’t always respected. “The minute [the NIH moratorium] was lifted, a whole bunch of things got published. It seemed like work had continued in the background,” said Lentzos.
The distant whiff of policies being considered that might limit scientific curiosity in any way is always bound to conjure discontent. The 1975 Asilomar Conference is often hailed as a historical moment when scientists working on recombinant DNA — splicing together genes from different organisms — stopped, considered the ramifications of their work, and then proceeded with new safety regulations in place, but even this supposed paradise of responsibility received staunch criticism. The famed molecular biologist James Watson warned colleagues that they were “defer[ring] research on the basis of unknown and unquantifiable dangers”. He feared that the conference had stirred irrational fears of recombinant DNA and declared in a later debate that he’d “eat grams of any K-12 strain carrying recombinant DNA rather than be licked by any neighbor’s dog.” Similarly, critics of the move to halt mirror life research, while quieter, do exist.
“I don’t go running around screaming, ‘This isn’t a problem!’” said Andrew Ellington, a biochemist and synthetic biologist at the University of Texas. Ellington is keen to emphasize to me that he likes and respects many of the scientists who are raising the alarm about mirror life. However, he said, he does not agree with their conclusions.
“If we were to somehow transport ourselves to a mirror world where everything at the molecular level was opposite, how well would we survive? The answer is: not very well,” he said. “You can’t just be not of this world and thrive. You’re going to have fierce competition from natural organisms, and you’re not going to be able to use the same food supplies and nutrients as everything else. I think this is not dealt with in as serious or deep a manner as it should be by the proponents of the moratorium.”
“It wasn’t like someone came to me and said: ‘You must not do it, because it will kill everyone.’ It was very gradual.”
Alexander Titus, a computational biologist and commissioner on the National Security Commission on Emerging Biotechnology (NSCEB), described mirror life as a “doomsday scenario” that “distracts from solving real, measurable” biothreats. He added, “There are real risks, and there are hypothetical risks. We haven’t even dealt with all the real risks yet.” Ellington echoed these sentiments: “We just had a pandemic ravage the world. Is that not where our attention, efforts and money should be going?”
Ellington fears that taking such pre-emptive action on mirror life may forestall promising avenues for scientific research and potentially invaluable discoveries. “The transistor led to computers, the internet, and all the good that came from those. Should we have stopped it way back then, because eventually, at some point, it will cause problems with how young people perceive themselves [on social media]? Folks say mirror life will be catastrophic, but I worry that we’re talking about this 25 years in advance. What else are we preventing?”
Ting Zhu, a molecular biologist at Westlake University in China, has spent a decade working toward the creation of a mirror-image ribosome, a feat now being debated as a potential red line. A mirror ribosome — essentially the 3D printer of the cellular world — could churn out mirror peptides and, some scientists think, drastically accelerate the pharmaceutical discovery of novel mirror peptide drugs. In a 2025 paper, Zhu wrote that his lab was still “years away” from achieving it. But Glass warned that if they succeeded, it would be one giant step toward enabling mirror life. “Make that mirror ribosome and the 10-30 year timelines change,” said Glass. Zhu declined an interview but directed me to an article he wrote for Nature last September, in which he warned against hasty bans, writing: “ … it is important not to let concerns and anxieties obscure our judgment of the underlying unknowns.”
There is a sense in which this may be as much a difference in philosophical worldview as it is a difference in scientific opinion. An investor in the Mirror Biology Dialogues Fund — the organization tasked with investigating and subsequently raising the alarm about mirror life — is Coefficient Giving (formerly known as Open Philanthropy), a research and grantmaking foundation philosophically aligned with Effective Altruism (EA). EA is a complicated movement with a wide range of beliefs, but at its core, it is about ensuring that charitable donations are spent with clinical efficiency by rigorously assessing issues to maximize positive impact. According to Coefficient Giving, their global health interventions have “saved over 100,000 lives, mostly of children under 5.”
But a key yet controversial cause area of both EA and Coefficient Giving is “longtermism”: the idea that one shouldn’t just care about the welfare of humans thousands of miles away, but also the welfare of humans thousands or even millions of years in the future. For longtermists, major existential threats, no matter how mathematically unlikely, are therefore a key cause of concern. For so-called “strong longtermists” these issues are the moral issues of our time, to be prioritized ahead of pressing current concerns such as climate change, wars and global poverty. Toby Ord, a key thinker in the EA movement, has identified AI and biosecurity as the two major contributors to existential risk, and Coefficient Giving has donated more than $400 million to both causes. In recent years, longtermism has become a hugely influential ideology in the tech industry, even among those who appear to be driving us fastest toward the AI apocalypse.
When viewed from the lofty and number-crunching perspective of a strong longtermist, one can see how definite problems of the here and now could be usurped in urgency by the incredibly slim yet non-zero possibility that mirror life could endanger the future of the countless unborn humans who will live on Earth during the roughly one billion years that it is expected to remain habitable.
“Biosecurity has always been an underappreciated and under-resourced field,” Titus, the commissioner at NSCEB, told me. “We have billions of dollars in missile defense, but we do not invest in biosecurity in the same way. So latching onto a global moment is the only way to really get meaningful attention on biosecurity. But my qualm is that it’s starting to become the boy who cried wolf.”
There are myths in almost every culture that warn us that it is possible to know and desire too much for our own good. Whether we’ve engaged with them deeply or superficially, the stories of Adam and Eve, of Prometheus, Icarus and Faust are inscribed on our souls. And whenever science and technology enter dark and uncharted waters, it becomes common to look back upon these stories like stars in the night’s sky, hoping for some sort of guidance.
“There is a lot we don’t know, and we could still be wrong. But do you really want to risk it?”
“There is a real deep uncertainty underlying all science. Not just superficial uncertainty, which is bad enough. But a real deep sense: We do not know what we’re doing,” the bioethicist Zoloth told me in the final interview I conducted for this article. Alongside her work as a bioethicist, Zoloth is a religious scholar, and she told me she feels the porous boundary between the two. “We thought there wasn’t a finitude to science, but right now it feels to me that mirror life could be the apotheosis of the project itself. Maybe in science, there are some things that it is impermissible to know; maybe artificial general intelligence will be another category like this. Perhaps we are now uncovering forbidden knowledge.”
The problem with the moral intuition that there may be some knowledge out there that we simply should not know is that it’s difficult to know what knowledge that might be in advance. He Jiankui, the Chinese scientist who caused outrage in 2018 by producing the world’s first gene-edited babies, believed his experiments would lead to a Nobel Prize. Instead, it led to three years in prison for him and slightly lesser sentences for two of his colleagues. Now free, He still believes that one day he will be viewed as a pioneer, while critics believe he opened a “Pandora’s box” that could one day lead to designer babies and eugenics.
Zoloth, with the air of a raconteur, had one more story to share before we ended our chat. She told me that she and her brother loved to play with a musical jack-in-the-box as children. “It was endlessly thrilling to us,” she said. “My brother, being my brother, wanted to know how it worked. So we very carefully took it apart. And then what we had were all these pieces on the ground, and we had no idea how to put it back together. We’d destroyed this thing we really loved. Sometimes I think about this story in relation to synthetic biology. We’re really good at taking things apart, but once we’ve done it, all we have left are broken pieces. Of course, my brother went on to become a great scientist. And I went on to worry about those pieces.”
