Think of life as we know it as a vinyl record. We listen to the A-side, with genetic material made from right-handed nucleotides and proteins composed of left-handed amino acids. Natural life has evolved to only use this configuration. These biomolecules are chiral<\/a>: they can\u2019t be superimposed on their mirror images. All life uses the same chirality. The hope, and fear, is that the opposite \u2014 synthetic life based on left-handed genes and right-handed proteins \u2014 exists on the bonus B-side of the record.<\/p>\n As my former colleague Kelsey Piper explained<\/a> back in January, mirror life could represent a whole new way that the world could end.<\/p>\n We\u2019re at least decades away from being able to create entire mirror cells \u2014 that includes bacteria. The technologies that would allow us to do so aren\u2019t yet up to the task. But we\u2019ve encountered<\/a> mirror biomolecules like right-handed amino acids in nature, and scientists have synthesized mirror enzymes capable of reading<\/a> mirror genes. With the power of chemistry, researchers have created<\/a> mirror proteins.<\/p>\n These mirror biomolecules are the building blocks of mirror life, but they are not mirror life itself. This distinction is really important, and not only because I\u2019m being pedantic.<\/p>\n A paper<\/a> published in Science last year made<\/a> dramatic<\/a> headlines<\/a> after its authors laid out potential catastrophic risks of mirror life. Such risks include the possibility that mirror bacteria would evade our immune systems and lack natural predators, replicating to the point that they threaten to outcompete normal life. The authors concluded that \u201cin the absence of compelling evidence for reassurance, our view is that mirror bacteria and other mirror organisms should not be created.\u201d<\/p>\n So if those are the risks, then we definitely shouldn\u2019t pursue the creation of mirror life. Right?<\/p>\n Well, only if we accept that those are the risks.<\/p>\n Something that\u2019s gotten a bit lost in the noise of media coverage is that the 35+ authors \u2014 who hail from fields as diverse as ecology, immunology, and synthetic biology \u2014 want mirror biomolecule research to continue. Nearly everyone agrees on that, because mirror biomolecules can offer immense benefits for developing new therapeutics, diagnostics, and studying the biochemistry of life without making new life itself.<\/p>\n The (brief) argument against mirror life<\/strong><\/p>\n But first, let\u2019s get into why the idea of mirror life is so frightening.<\/p>\n Kate Adamala<\/a>, a biochemist building synthetic cells at the University of Minnesota and the lead author of the Science paper, received a 2019 grant to develop and deploy mirror cells. Upon looking into it further, she decided that the risks far outweighed the benefits, and called for the work to be halted.<\/p>\n \u201cMirror molecules are safe to make, because unlike mirror bacteria, the molecules don\u2019t replicate, so they don\u2019t pose any risks of spreading uncontrollably,\u201d Adamala told me over email. One of her chief concerns is that normal cells may be unable to recognize mirror cells, because many of our immune mechanisms are based on chirality, or handedness. This could allow mirror cells to \u201cgrow unrestrained by the immune system and environmental predators\u201d that keep normal cells in check.<\/p>\n \u201cIt\u2019s hard to overstate how severe these risks could be,\u201d Ruslan Medzhitov, an immunologist at Yale University and one of the paper\u2019s co-authors, told<\/a> Science News. \u201cIf mirror bacteria were to spread through infected animals and plants, much of the planet\u2019s many environments could be contaminated. \u2026Any exposure to contaminated dust or soil could be fatal.\u201d<\/p>\n We could see a mass extinction event, an existential threat to multicellular life as we know it. Effective biocontainment, the researchers argue, would be incredibly difficult. If you have the time, it\u2019s worth reading the 299-page technical report<\/a> that explains how the study authors came to their conclusions.<\/p>\n That said, mirror life could offer real benefits. Mirror therapeutics, which wouldn\u2019t be recognized by our digestive enzymes, have the potential to last a lot longer in our bodies, opening up new possibilities for the treatment of chronic disease. Right now, we create mirror therapeutics chemically, putting them together atom by atom. Mirror bacteria could do this for us, and at a much greater speed, allowing<\/a> us to produce mirror therapeutics en masse.<\/p>\n Synthetic biology and synthetic chemistry are relatively small fields, and mirror biology is even smaller. The declarations of a scientific consensus around mirror life may be premature, but a growing number of voices are getting involved in discussions on the possibility.<\/p>\n I want to make it very clear that right now, mirror life is only a possibility. And it might be more distant than we think. David Perrin<\/a>, a synthetic chemist at the University of British Columbia, told me over email that science is nowhere close to creating a living mirror cell.<\/p>\n He is also skeptical that mirror bacteria would be toxic to normal life, and believes our immune systems would likely be able to neutralize them after all. Immune responses are complex, and not all rely on handedness.<\/p>\n The scale of the threat is unclear, because mirror organisms might be hopelessly outcompeted by regular life. By creating a second tree of life, we might create a second evolutionary arms race, with mirror life on the losing side. Mirror organisms might struggle to find food they need to proliferate. Or not \u2014 evolution is a funny thing \u2014 but at this point there\u2019s no way to know for sure.<\/p>\n \u201cThe more I think about this, the more I realize that the real concern ought to be with creating life on this side of the mirror,\u201d Perrin told me. Trying to shut down work on creating mirror life \u201cmakes no sense. \u2026What would have happened if we put a total moratorium on researching radioactivity? We wouldn\u2019t know anything about RNA. And we wouldn\u2019t have any radioactive treatments for cancer.\u201d<\/p>\n He thinks that red lines can be drawn \u2014 when people come closer to actually generating mirror life.<\/p>\n Gigi Gronvall<\/a>, an immunologist and senior scholar at the Johns Hopkins Center for Health Security, and biosecurity expert at Johns Hopkins University, told Science News that the paper\u2019s concerns were very theoretical. While she strongly supports the authors\u2019 advocacy for discussion around the issue, she thinks that any proposed funding and research ban \u201cputs the cart before the horse\u201d and could impede research leading to surprising scientific advances.<\/p>\n We don\u2019t fully understand the risks of mirror life, and we won\u2019t without more research. But this research could be purely computational<\/a>, allowing us to assess the nature of potential threats without posing real biological risks.<\/p>\n\n