The startling announcement by He Jiankui almost one year ago that he had created the first genetically modified human beings unleashed a torrent of criticism. It also brought to the surface common misunderstandings — even among scientists and ethicists — that reproductive uses of this genome-modifying tool have therapeutic value, will treat people with genetic disorders, will save lives, and will eradicate disease. None of those are true.

The twin girls that He helped create are publicly known as Lulu and Nana. Their father is HIV-positive. The scientist said he used CRISPR-Cas9 genome editing technology to disable a gene called CCR5 to mimic a naturally occurring gene deletion that appears to confer immunity against HIV.

A major criticism from the scientific community, which has otherwise been generally supportive of advancing gene technologies, was that He did not use the technology to address a serious medical need. That criterion stems from a 2017 report by the U.S. National Academy of Sciences and the National Academy of Medicine recommending that, once the technology is ready and safe, genetic modification of embryos could be allowed when there is a “serious disease or condition” to be addressed and no “reasonable alternatives” exist.


This scientific criticism of He’s experiment was on target: Although HIV infection is a serious disease, there are proven ways to prevent transmission of the virus from an infected father to his offspring, and later in life to prevent or treat the infection.

That said, scientists criticizing He on the grounds that he did not treat a serious condition with no alternatives imply that other applications of CRISPR to modify eggs, sperm, or embryos could meet this standard. Indeed, many scientists hail reproductive applications of CRISPR (what I call rCRISPR) as potentially lifesaving and curative.

As I argued recently in the journal Bioethics, that claim for rCRISPR is mistaken and misleading. rCRISPR does not save lives or cure diseases that would otherwise exist. It merely aids in creating a person without a particular genetic disease who would otherwise not exist. The value here in creating healthy people — as opposed to healing people who would otherwise be sick — is nominal to none. If you are a genetically healthy person, you have a high chance of creating a healthy person right now. But nobody thinks you have an urgent moral reason to do so.

Let me be clear: I believe there are applications of CRISPR that do correctly purport to cure diseases in people who would otherwise have them. CRISPR-based gene therapies known as somatic applications, which are used in the bodies of people who have genetic diseases, have great curative potential. These aren’t the target of my critique. In fact, it would be much better if we invested the money spent on reproductive CRISPR applications on somatic ones instead.

Here’s why I say that using rCRISPR to modify eggs, sperm, and embryos does not cure disease.

Imagine an individual or couple at high risk for creating a child with a serious genetic disease. They have the following simplified range of options:

  1. Create a genetically related child in the time-honored fashion who will be at high risk for the genetic disease.
  2. Create a genetically related child using CRISPR who will be at very low risk for the genetic disease.
  3. Create no genetically related child.

The existence of option C undermines the claim that rCRISPR applications are lifesaving or curative. If the prospective parent did not have option B available to them, option A would not inevitably happen, meaning they would not inevitably have a sick child. Individuals have a choice in the matter of creating children at high risk of genetic disease: They can choose option C.

Here is a different way of seeing the point that rCRISPR is not morally urgent because it does not involve a child whose existence, or illness, is inevitable. Compare the following scenarios: A doctor creates a cure for a serious and debilitating disease and administers it to a seriously sick child, thus healing her. This doctor saved a life, a morally commendable action. Now imagine that the doctor first injected the disease into the child that he cured. Now his action in its totality could hardly be called curative, for he first created the harm. His seemingly heroic act of healing now has dubious moral value.

This is similar to what occurs with rCRISPR. A clinician first creates an embryo with genetic defects, and then “rescues” it using rCRISPR. Calling this a cure or a therapy is a nonstandard use of those concepts, one that warrants a distinction from standard cures that save lives and prevent otherwise probable harms.

The analogy shows that an otherwise good act or cure can have its moral value undermined if it is part of a greater act that caused the disease in the first place.

Saying that people at risk for passing on serious genetic disease to their offspring can simply not have genetic children at all may seem harsh. But there are several options available to such individuals for becoming parents. They could adopt a child, an often-overlooked opportunity to become a parent that also helps an existing child in need of a family. They could use the egg or sperm of a healthy donor to create a child. Both of these options are expensive, but not more so than rCRISPR.

Prospective parents could also create genetically related children using pre-implantation genetic diagnosis. In this process, an individual’s eggs or sperm are used in conjunction with a partner or donor’s gametes to create several embryos that are then genetically screened for the disease in question. Only healthy embryos are implanted for pregnancy. Pre-implantation genetic diagnosis is a safe technology that is being used today.

Reproductive applications of CRISPR simply cannot meet the criteria laid out by the U.S. national academies. They will not address a serious condition, because rCRISPR is used in the creation of a person who does not have to exist at all. Nonexistence is no condition, and thus not a serious one.

The real value of rCRISPR is not to the individual who is created but to the people who choose to use it to create a child. It helps individuals achieve their reproductive preferences by having genetically related children free of genetic diseases. But this preference, although perhaps deeply held by many, is not a medical need or an urgent one. And pre-implantation genetic diagnosis already enables people to meet this preference.

We should object to the investment of precious medical resources in bringing rCRISPR to market when there are serious and urgent medical needs that could be met elsewhere, including investing in somatic gene therapies that actually treat diseases.

Tina Rulli, Ph.D., is an assistant professor of philosophy at the University of California, Davis, and a member of the UC Davis Ethics Commons.

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  • Hi Tina,

    I have a question about the analogy of the clinician “first creat[ing] an embryo with genetic defects [and] then rescu[ing] it using rCRISPR”. If a clinician were to use rCRISPR, do they have to first intentionally create an embryo with genetic defects? I guess I am confused about why they would need to do this.

  • Tina and dear readers, I would like to point out that technology is subjugated to good use and the free xhoice of those who need it. Deciding who uses what technology and for what is a fundamental human right. Depriving one person of access to that technology and further more even more people is not only a violation of fundamental human rights, and because it is done on purpose, it is called attempted murder in the case of those who are ill. Please answer me what are your opinions on depriving people of free choice and a healthy life. Money should be invested directly into science and research from all contributors, either states or private businesses and their direct effects (benefits) made accessible to the public immediately. What you are doing and saying is just opening an empty discussion while people die or are unable to have kids
    and debating their decisions. What I’ve wrote above is the only ethic that exists on this planet and what you are doing is wrong. You should be besides them helping them. One small act is enough to save a life. Implementing rules to prevent misuse is a snap as they can be delineated immediately. I don’t think we are facing the same crisis as the FBI wirh Kevin Mitnick in the 80’s.

    • Hi Andreea, We have a limited amount of medical and research resources to go around. So not everyone will be able to have their medical needs and desires satisfied. This is exactly why I’m arguing that investing in rCRISPR, which has low social value and impact (and doesn’t meet an urgent medical need, but rather satisfies a social preference for genetically related children) should not be our top priority. So I think we actually agree on some foundational issues–that people have a human right at stake to be healthy. In a world where many people do not have that right being met, we cannot spend our research dollars on a low impact technology.

  • One more thing. When we amputate one of our legs is because we don’t have a choice. With CRISPR we have all the choices in our hands.