We Should Tolerate and Regulate Clinical Use of Human Germline Editing


By Parker Crutchfield, PhD

In November of 2018, a Chinese scientist announced that he had edited the embryos of twin girls and that the twins had been born. The scientist, He Jiankui, used CRISPR, a revolutionary method of editing sequences of genes, to delete the gene CCR5 from the embryos’ sequences. The intention was to make the twins resistant to HIV. Editing human embryos and allowing those embryos to develop into living, breathing babies was widely condemned. However, now it appears possible, likely even, that the twins’ cognition was impacted, perhaps improved. This, however, was an off-target effect—it was unintended. On March 13, Nature published a comment from a group of scientists calling for a moratorium on clinical uses of human germline editing. This call is only for a moratorium on clinical uses, not on research on editing the human germline.

Despite the moratorium, I think a good argument can be made that tolerating the clinical use of human germline editing is morally permissible. Here is one such argument. The fact that He Jiankui edited the girls’ embryos suggests that it is inevitable that some scientists are going to engage in this behavior. Imposing a moratorium is unlikely to change this—the cat’s out of the bag. Given that the behavior is inevitable, we should ensure it is performed as safely as possible in order to reduce the risk of harm.


Image description: an illustrated image of a strand of DNA with a piece being inserted, representing CRISPR-Cas9 technology. Image source: NIH Image Gallery/Flickr.

The Inevitability Argument

I’m claiming that because clinical use of human germline editing is now inevitable, we should tolerate and regulate it. Generally, arguments of this type don’t work. It isn’t generally true that just because something is going to happen anyway, we should not only tolerate that behavior, but also make sure that it is done safely. For example, it’s true that humans murdering other humans is inevitable (unless we can cognitively or morally enhance people through, for example, gene editing!). Despite prohibitions on murdering, it still happens and probably always will. But its inevitability doesn’t mean that we should tolerate it but ensure that it is done safely. We shouldn’t, obviously.

Sometimes the argument does work, though. Sometimes the inevitability of a behavior suggests that we should tolerate it under regulation. For example, people using IV drugs is, for the foreseeable future, inevitable. Given this inevitability, it is morally justifiable to tolerate the behavior and do what we can to ensure that it is done safely. One way we do this is through needle exchanges. More recently, similar arguments support the widespread availability of naloxone for overdoses. So, sometimes, but not generally, the inevitability of a behavior justifies the tolerance of the behavior in order to ensure it is performed safely.

Reducing Harm

Why does the Inevitability Argument work in the case of needle exchanges? Why does it fail in the case of murder? One difference is that we know murder is wrong. You can’t have the concept of murder without also having the concept of wrongness. To tolerate murder would be to tolerate something that is morally prohibited. But we should be more skeptical of the wrongness of IV drug use—it may not be wrong at all, to say nothing of policies that permit or prohibit it. Even if it is wrong, our confidence that it is so should be lower. Another difference is that in the case of needle exchanges with IV drug users, the tolerance and regulation is meant to reduce harm, not only to the users, but to society. On the face of it, it seems implausible that one could anticipate a parallel policy of tolerating and regulating murder to reduce harm. Rather, tolerating and regulating murder would increase harm.

Inevitability of Clinical Use of Human Germline Editing

Is the clinical use of human germline editing more like IV drug use, or more like murder? Supposing that whether the Inevitability Argument works depends on whether we know the behavior being tolerated is wrong, and whether tolerating it is intended to reduce harm, the clinical use of human germline editing seems much more similar to IV drug use than it does to murder. First, we don’t know whether the clinical use of human germline editing is wrong, unlike our knowledge that murder is wrong. Whether it is wrong or permissible or obligatory depends on a lot of factors, including on whether embryos have a moral status and whether we have a duty to future persons.

Second, what would tolerating the clinical use of human germline editing look like? It would require scientific and political oversight of methods, data, and follow-up clinical care. But more importantly, the tolerance and regulation of the clinical use of human germline editing would require that we know more about what the effects of it will be. The only way we can acquire this knowledge is by conducting research on the clinical consequences of editing the human germline. This is all to say that the intention of tolerating the clinical use of human germline editing is to reduce as much as possible any potential harms, both to the person whose embryo was edited as well as to society.

Tolerating and Regulating Clinical Use of Human Germline Editing

By these criteria, the clinical use of human germline editing looks much more like needle exchanges for IV drug use. If so, then the Inevitability Argument may work, suggesting that we should tolerate and regulate its practice. But this tolerance and regulation impose further requirements: we must closely monitor the behavior and support research on the effects of editing the human germline.

Scientists assert (without sufficient foundation, I think) that the behavior is wrong. Do we really know that the clinical use of editing the human germline is wrong? If so, what general principle grounds this knowledge? What are the consequences of this general principle for other lines of scientific research? Is the clinical use of human germline editing really inevitable?

parker-crutchfield-cropParker Crutchfield, PhD, is Associate Professor in the Program in Medical Ethics, Humanities, and Law at the Western Michigan University Homer Stryker M.D. School of Medicine, where he teaches medical ethics and provides ethics consultation. His research interests in bioethics include the epistemology of bioethics and the ethics of enhancement, gene editing, and research.

Join the discussion! Your comments and responses to this commentary are welcomed. The author will respond to all comments made by Thursday, April 18, 2019. With your participation, we hope to create discussions rich with insights from diverse perspectives.



  1. Lander, E. S., Baylis, F., Zhang, F., Charpentier, E., Berg, P., Bourgain, C., … Winnacker, E.-L. (2019). Adopt a moratorium on heritable genome editing. Nature, 567(7747), 165–168. https://doi.org/10.1038/d41586-019-00726-5.
  2. Marchione, M. (2018, November 26). Chinese researcher claims first gene-edited babies. Retrieved April 2, 2019, from https://www.apnews.com/4997bb7aa36c45449b488e19ac83e86d.
  3. Regalado, A. (2019, February 21). China’s CRISPR twins might have had their brains inadvertently enhanced. Retrieved April 2, 2019, from https://www.technologyreview.com/s/612997/the-crispr-twins-had-their-brains-altered/amp/.

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