In late 2024, a group of biologists stopped their work and asked colleagues to do the same. They were worried that their research on “mirror life”—cells and organisms with artificial mirrored versions of DNA and proteins—could create bacteria that would be so unidentifiable that immune systems would fail to recognize them as warranting attack. Even though the research on mirror DNA and proteins was promising, these scientists decided the risks to continuing their inquiry were too high.
It might seem extreme for biologists to ask each other to drop their investigations, but it has happened before. In 1974, biologists stopped research on recombinant DNA out of concern that this innovation—splicing together genes from different organisms—could endanger the future of humanity. The voluntary pause was lifted after a meeting in 1975, at the Asilomar Conference Grounds in Pacific Grove, California, laid the groundwork for regulations to safely practice genetic engineering. The meeting only lasted four days, but it impacted the field of molecular biology for the next fifty years.
Biological inquiry has moved incredibly rapidly, especially in the last few decades. Researchers have identified most of the thousands of genes in the human genome, figured out what a lot of them do, and developed medicines based on these genes and the proteins for which they code. To do that, they had to study individual genes, which required clever DNA manipulation. In our body, DNA exists as giant molecules, which are tightly folded up like a strand of Christmas lights still new in their box. But these unwieldy large structures make it hard to study individual genes, which each only take up a small fraction of the DNA molecules.
That changed by 1972, when Paul Berg, Stanley Cohen, and Herbert Boyer discovered how to cut a piece of DNA (such as a gene) from one organism and paste it into a piece of DNA from another. With these recombinant DNA techniques it was now possible to study any gene within a small piece of DNA in bacteria. Biologists were thrilled about what this could mean.
“The impact of this new capacity to move pieces of DNA between species at will was immediately understood by molecular biologists in the dual scientific and practical terms that characterized the perceptions of its inventors,” writes science historian Susan Wright. Even if the researchers behind this molecular cloning technique were mainly driven by curiosity and the desire to learn more about the natural world, there was also a clear benefit for industry. Yet, they were also wary, realizing that these newly discovered DNA editing methods had the potential to be used in nefarious ways. If someone could take any piece of DNA and insert it into a virus or bacteria, they could create uncontrollable pathogens.
“In this field, unlike motor car driving, accidents are self-replicating and could also be contagious,” Wright explains, quoting biologist Sydney Brenner. Similarly concerned, molecular biologists Maxine Singer and Dieter Söll asked the National Academy of Sciences (NAS) to create a committee to recommend guidelines for recombinant DNA research. The NAS invited Paul Berg to lead this committee. As department chair and biochemistry professor at Stanford, Berg was a familiar voice in the community, and since his lab established some of the early recombinant DNA technology (for which he would win a Nobel Prize in 1980), he clearly understood the work. The new committee immediately urged researchers to stop some of the riskiest research on recombinant DNA.
“There is serious concern that some of these artificial recombinant DNA molecules could prove biologically hazardous,” the committee wrote in a letter to fellow scientists. They followed it up with recommendations to stop work on the kind of genetic engineering that could lead to the spread of recombinant bacteria or viruses. The committee also suggested that the National Institutes of Health (NIH) oversee a plan to evaluate the risk and minimize the threat, and they called for an international meeting to discuss next steps on the matter.
That international meeting took place in February 1975, at Asilomar. It drew about 150 attendees, including both scientists and journalists. The latter were asked to wait until the end of the meeting to file stories rather than cover the debates as they happened.
“It would be silly to try to cover the meeting as a running story,” the Washington Post’s Stuart Auerbach told The Hastings Center Report, “and my paper, I’m sure, would soon have been bored with daily stories.”
Had daily coverage been allowed, there would likely have been much to report. Rolling Stone’s Michael Rogers, who attended, found inspiration at Asilomar for an entire book, Biohazard. In a review, Dennis J. Helms praises Rogers’s descriptions of the meeting’s proceedings.
“One is able to see how difficult it was to conduct the Asilomar Conference on the assessment of risks hypothesized to be associated with this research,” Helms notes, “when some of the scientists could not even understand what others, outside their specialty, were saying.”
While Berg or Brenner understood the science, it was still very new to many meeting attendees—even those who were biologists. Not everyone was caught up on recombinant DNA technology. And none of the researchers, not even the recombination experts, could know which aspects of this new technology would genuinely pose a risk. The official summary of the meeting, published after its conclusion, acknowledges as much, stating that “the new techniques, which permit combination of genetic information from very different organisms, place us in an area of biology with many unknowns.” Even though not everyone could agree on how big the unknown risks would be, they nevertheless thought it was important to be prepared for come what may.
“A major advance coming out of the Asilomar Conference was the concept of biological containment,” wrote Bernard Talbot of the National Institutes of Health (NIH) in 1981, which called for “the use of organisms with limited ability to survive outside of the laboratory” in experiments. In other words, recombinant DNA should be inserted into organisms—at that time, mostly bacteria—that wouldn’t survive outside of their very controlled lab conditions. For example, Escherichia coli K-12 bacteria can’t survive among the E. coli that live in the human gut, so they’re considered low risk for biological research. This containment requirement as well as several other recommendations were worked into the NIH guidelines published a few months after the meeting.
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For those outside of the bubble of the biology world, the NIH guidelines represented their initial introduction to recombinant DNA and its perceived risks. Even though the meeting attracted biologists with different opinions on what was needed to safely use recombinant DNA, this discussion was among scientists only. There were no public interest groups involved, despite the fact that some related risks, such as the accidental release of new pathogens, was relevant to everyone. According to Priska Gisler and Monika Kurath, “historians argue that by keeping prominent dissidents out of the Asilomar discourse, the molecular biology community aimed to prevent external agenda setting.”
But there were dissidents within the meeting even so. Not all scientists welcomed the initial research ban or the regulatory constraints. “Many scientists feel that freedom of scientific inquiry is a constitutional ‘right’—like freedom of speech,” observes sociologist of science Dorothy Nelkin.
Even though there was no public debate on recombinant DNA until after the regulations were set, bioethicists and science communication experts still generally see Asilomar as an example of how scientists might take responsibility for reducing possible risks related to their work. And in spite of the imposed limitations, the decisions made at Asilomar opened the door for modern biological research.
As soon as new regulations, initiated at Asilomar, allowed researchers to work with recombinant DNA again, they used it to learn more about genetics. “The most profound consequence of the recombinant DNA technology has been our increased knowledge of fundamental life processes,” wrote Berg and Singer in a retrospective article in 1995. “No longer is the gene an abstract notion, nor is it as enigmatic as interstellar dark matter or black holes.”
Both the scientific and corporate worlds became mindful of the practical applications of recombinant DNA. Industry saw the potential for drug development, and molecular biology was suddenly a lucrative field. “What had been an area of basic research had undergone a far-reaching social transformation,” according to Wright. Thousands of academic and industry labs now routinely use recombinant DNA, and they still follow safety standards that came out of the Asilomar meeting.
Many observers consider Asilomar an exemplar of how scientists might debate risk and devise sensible guidelines; indeed, it set a standard for such conversations. Similar discussions about biology, safety, and ethics have subsequently taken place—and, crucially, have been more public—than the discussion at Asilomar. David Baltimore co-organized the first International Summit on Human Genome Editing in 2015 and noted how drastically it differed from the closed events at Asilomar.
“At the Summit, individuals sent blogs, tweets, and retweets as the discussion was taking place,” he writes. “The entire event was webcast around the world, and the video is available online for all to see.”
One of the concerns in 2015 was the impact of potentially manipulating gene drives—the processes that increase the chances that certain genes will remain in a population. Such an innovation could be used, for example, in pest control or to limit the spread of disease. It would also open the door to ethical concerns regarding whether such manipulation would disturb ecosystems. For example, gene drives could eradicate a population of disease-carrying mosquitoes, but removing an entire population of one species from a local ecosystem could have a knock-on effect that disrupts other species as well.
Unlike in Asilomar, the debate and regulation of gene drive research wasn’t fully in the hands of the scientists who worked with the techniques. Rather, environmental groups asked for a moratorium on this research. When members of the scientific community and the environmental watchdog community eventually reached an agreement in 2018, they tried to find a balance between the public’s worries and the technological advances.
Another area of concern is synthetic biology—the creation of new molecules of life. In 2006, Jonathan Tucker and Raymond Zilinskas wrote in The New Atlantis that “synthetic biology is at roughly the same level of development as molecular genetics was in the mid- to late 1970s.” They drew parallels with the recombinant DNA saga to illustrate why it was important to carefully regulate synthetic biology.
One of the risks of synthetic biology is that it makes it possible to create entirely new bacteria with new molecules. These could be pathogens, so they have to be contained. But now imagine going further still into the realm of the astonishing, and creating not just molecules that resemble naturally occurring ones, but their exact mirror images which are not naturally found anywhere on Earth. That’s the current concern around mirror life.
Creating mirror bacteria with mirror DNA and mirror proteins could have some potential benefits. Some medications are based on molecules that are mirror images of natural molecules. They could be made in a chemistry lab, but mirror bacteria might make it faster and cheaper to create such drugs at scale. But mirror cells wouldn’t fit in their regular, unmirrored environment. Should bacteria with mirrored molecules escape from their labs, they would be unrecognizable to our immune systems, which would be powerless against it.
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That fear of creating a creature that can’t be controlled drove researchers to call for a self-imposed moratorium on any further mirror life experiments in 2024. It’s a lot like what happened in the 1970s, but the way that the scientists at Asilomar set their own guidelines for recombinant DNA couldn’t exactly be replicated for synthetic biology, argues Emma Frow. For example, biosecurity is now a major concern requiring input from people outside of the biology community.
There are no current plans to lift the ban on mirror life research. In February 2025, scientists got together at Asilomar again to mark the fiftieth anniversary of the meeting. They talked about many of the current issues in biology, and agreed that mirror life is still much too risky to study. But if there is a resolution to lift this ban at a future date, it would likely differ from the resolution that followed the research stoppage regarding recombinant DNA. For one thing, we can expect public representatives to have a much bigger voice in the discussion. Still, the events surrounding Asilomar taught biologists that they can call on their community to halt potentially dangerous research—a course of action scientists may still choose to follow today.
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