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New technologies can help athletes push boundaries and test physical limits. Sometimes, they challenge deeply held notions about the “spirit of sport” and what it means to compete on a fair and equitable playing field. In the past decade, we’ve seen debates over the fairness of everything from cutting-edge to “.”

But those technologies may seem like nothing compared with fast-approaching methods of using tools like CRISPR, a method of genetic editing, to design future athletes. With the taboo on human gene editing in the process of being shattered, children whose genomes have been modified before birth in order to give them a competitive advantage later in life could be born in the next few years. Some of these individuals could conceivably be of age to compete in the 2040 Olympics. (For many events, the minimum age ranges from 14 to 17 years old. Others, like swimming, have no age requirement.) Those cases would be outliers, to be sure—but they may nevertheless emerge, and we are neither ready for gene-edited athletes nor prepared for how individuals and/or countries might start taking unknown and undefinable risks to get there.

In theory, gene editing could enable fine control over how the human body grows and where someone’s maximum potential lies. It could or the proportion of the body’s muscle designed for bursts of energy—a big potential advantage in many track events, swimming, or gymnastics. For endurance events like cycling or long-distance running, athletes could go farther and for longer before getting tired if their genes enable the blood to carry more oxygen. Many of these possibilities are still hypothetical and the science is still relatively immature, but they’re worth thinking about now.

And gene-editing technologies are developing at a breathtaking pace. Just over a year ago, twins whose genes had been were born in China. In October, other researchers unveiled “,” a new technique that is more accurate than CRISPR. And despite global calls for caution, Russian scientist Denis Rebrikov and others have continued to with plans to continue testing gene editing in humans. The field is almost as competitive, though probably not as richly rewarding, as the world of international sport, which has a history of state-sanctioned doping programs. That may mean that in the 2040 Olympics or soon after, every conceivable record could be broken. But that’s only half of the problem. Those records would only be shattered if the edits work as planned. The mere assumption of what is achievable often drives the use and misuse of new technologies. If people, whether parents or governments, believe that gene editing can easily add or remove specific traits, it will likely end in attempts to enhance the next generation of athletes sooner rather than later.

Athletes and nation-states already pay close attention to genetics and biotechnology in sports. Scientific American has reported that shortly before the 2008 Summer Olympics, a scientist known for gene therapy research received from athletes seeking a genetic edge in the competition, even though the technology is largely untested and potentially unsafe. In 2018, China that it would use athletes’ full genomes as a factor when considering their eligibility for the 2022 Winter Olympics team. The possibility of genetic forms of cheating spurred the World Anti-Doping Agency to expressly ban genetic doping in its Prohibited List. It’s also created to monitor and punish adult athletes who try to enhance themselves. But the WADA measures make a very specific assumption: that the athlete has decided to do this on their own. They likely don’t apply to athletes whose genetic modification took place before they were born.

When combined with the growing attention being paid to genetics in sports, as we argue in a new paper published in the , the hype and allure of embryonic gene editing is likely to create serious political and economic temptations for countries and/or parents to start “genome doping.” Countries often see performance at the Olympics as a proxy for in the international community, and as a result, those seeking to increase or maintain their political and economic status could well be driven to develop covert genome-doping programs. The same holds true for parents, even if it’s on a smaller scale, at least to start with—having a world-class athlete as a child brings fame, perhaps financial stability (depending on the sport), and pride. It will be unfathomably expensive initially, but there are very wealthy people who want to see their children succeed in competitive sports. And for decades, international sporting events have been a place where athletes and their countries and coaches have used cutting-edge science and technology in search of getting ahead of the pack. Almost 70 years ago, for instance, Soviet weightlifters and wrestlers using new supplements were able to take home eight Olympic gold medals.

But this is risky. Editing genes before pregnancy begins will be much more complicated than taking a course of hormone supplements. Athletic performance doesn’t flow from just one or two genes. Instead, or more all work in concert to create athletic potential. And whether this potential translates into performance depends on many other factors, including environment, training, nutrition, and the . A handful of individual genes have known connections with athletic features such as better endurance and lower chances of injury, but scientists still have a lot to learn about how those genes work and which other genes they interact with.

Limited understanding of how new performance-enhancing technologies affect the body hasn’t stopped athletes or countries from using them in the past. In the late 1980s, for example, cyclists began using new methods of blood doping to increase their endurance—and continued even after reports in the early 1990s that up to may have died from complications. Definitively linking doping to the cyclists’ deaths has proved complicated in retrospect, but the case still highlights how athletes hastily employed new and untested technologies in order to gain a competitive edge without knowing whether they could cause serious harm.

This is a pattern that isn’t just limited to individuals. A long and controversial history of countries—including East Germany, China, and Russia—engaging in doping programs suggests that governments can be just as willing to take risks with their athletes’ health as the individuals themselves are. Such programs are not a thing of the past, as highlighted by WADA’s decision this week to . Some, like China, have even been athletes to dope with high doses of drugs over long periods. History suggests that some government-backed sporting programs, uninterested in athlete health or consent, might see few ethical issues with gene editing if there is even a slight potential to increase the performance of future athletes.

That could put them at significant risk. Even if the correct areas for treatment are found, various CRISPR gene-editing tools are liable to make edits in the genome—unintended changes that could lead to disease or dysfunction in humans. While new “prime editors” could be more accurate, mistakes will still occur, and much more research is needed to assess their benefits and limitations. Even if only intentional edits occur, they could still cause health consequences. For example, while the modifications made to the twins born in China could reduce their immunity to some , they were previously thought to have shortened their life spans as well. However, the data supporting this conclusion have recently been , illustrating exactly how complicated all of this is.

It’s not clear how the international sporting community will, or should, react. We don’t even know how gene-edited athletes could be detected—something that may well lead to regulations requiring whole-genome screening for athletes. This raises particularly thorny issues around if and when gene editing is used to confer a naturally existing but helpful genetic variant—something that already exists but is enhanced in gene-doped athletes. And this is where more complex social and ethical challenges are likely to arise. If athletes who have been gene-edited before birth are detected, will they be barred from competing out of “fairness” to others or to discourage the practice of human gene editing? Or will they be required to take drugs to suppress their abilities, bringing then back down to “normal” levels—as happened to sprinter this year? As embryonic gene editing becomes increasingly accessible, who will decide what “normal” is?

With no clear legal or ethical pathways forward, society is ill-prepared for the very real possibility of genome doping in athletes. As a first step, anti-doping agencies like WADA should be convening expert groups to design rules that work across cultures and incorporate the best available science on gene editing and its potential impacts. Beyond this though, bodies such as the World Health Organization and UNESCO need to develop a set of norms and expectations of embryonic gene editing, including reference to athletics. Without this deliberative debate and norm setting, we collectively run the risk of turning a blind eye to the use of a technology that, if not implemented responsibly, could lead to a legacy of destroyed lives.