Human Gene Editing Frequently Asked Questions

Recent genetic engineering developments are raising an urgent question: Should we as a society condone the genetic modification of future human beings?

Here we take on some common questions about the prospect of using gene editing, along with assisted reproductive technologies, to produce genetically altered children.

For key developments and position statements in 2015, visit our About Human Germline Gene Editing resource page and see Genetically Modified Humans? 7 Reasons to Say No

  1. “What’s wrong with creating genetically modified humans?”

    CGS: Efforts to genetically engineer future children and generations would be unsafe, medically unnecessary, and profoundly damaging to social justice and human rights.

    Human germline gene editing would constitute inherently unsafe human experimentation, putting any resulting children at extreme risk of harm and effectively irreversible genetic changes. It would distort family and other relationships by encouraging notions of human beings as biologically perfectible artifacts. It could all too easily lead to a future society of genetic “haves” and “have-nots,” with new forms of inequalities and biological discrimination on top of already existing ones.
  2. “But can’t germline gene editing cure devastating genetic diseases?

    CGS: By definition, germline gene editing does not treat or cure anyone.

    It would change the genes of embryos produced with in vitro fertilization, but not of patients with a diagnosed disease. Gene editing that aims to treat or cure patients, by contrast, would target the somatic (body) cells of an existing person with a genetic condition.
  3. “What about parents who want to prevent children from being born with serious genetic conditions?

    CGS: Parents can have healthy children who are genetically related to them without the risks of germline intervention.

    Some people at risk of transmitting a genetic disease decide to adopt or to have children using third-party eggs or sperm. Couples for whom a full genetic connection is important can use embryo screening techniques like pre-implantation genetic diagnosis (PGD), which tests embryos produced with in vitro fertilization; only those unaffected by the genetic variant of concern are used to start a pregnancy. Using PGD to select children who have – or who lack – specific traits raises its own ethical concerns, but PGD is far safer and less socially consequential than manipulating the genes of future children.

  4. “Will parents be able to engineer their children to be smart, tall and blue-eyed?”

    CGS: Most traits are affected not just by multiple genes but also by other biological, social and environmental factors. Yet there’s ample reason to be concerned.

    It’s important to recall that many aspects of human appearance, behavior, and cognition involve large numbers of genes, and are heavily influenced by environmental and social conditions. For example, dozens of genes are associated with height. But it’s also important to keep in mind that scientists have successfully created animals with modified traits, including primates (see Question #5 below). And new genome editing tools allow much easier modification of multiple genes in the same cells. An additional concern is that children who are thought to be “improved” or “enhanced” through genetic alteration may be treated differently – either for better or worse – and that this in itself could encourage new kinds of social stratification.
  5. “Don’t animal studies prove that the technology is safe and works well?”

    CGS: Some experiments have been done, but certainly not enough to guarantee safety.

    Experiments with human germline intervention could lead to miscarriages, maternal injuries and stillbirths. Genetically modified children who seemed healthy at birth could develop serious problems later in life, some perhaps introduced by purported “enhancements.” Harmful consequences of germline modification might only present themselves in subsequent generations. Scientists have used previous-generation genetic engineering tools to produce GM animals, including rabbits that “glow in the dark” because of an inserted jellyfish gene, mice that run mazes faster than their unmodified counterparts, and goats that produce spider silk in their milk. Researchers have recently used CRISPR gene editing to produce genetically modified monkeys, to alter 62 copies of the same gene in pig embryos in efforts to make them suitable for organ transplants into humans, and to remove a gene in dog embryos to produce beagles with double their normal muscle mass, with proposed uses including novelty pets and enhanced police and military canines. But experience with cloning suggests that responses to genetic engineering vary considerably among species.
  6. “So why would anyone want to genetically modify their future children?”

    CGS: Some might be attracted by the idea; others might feel obligated to give their children a competitive edge.

    Perhaps because the medical argument for germline gene editing is so unpersuasive, some propose using it for enhancement. One prominent scientist suggests that gene editing can give future children traits such as harder bones. A group of bioethicists recently proposed using “human engineering” to make people smaller, and to give them night vision, in order to lower our environmental impact, calling it “potentially less risky than geoengineering.” Some enthusiasts argue that genetically enhancing future children will be a “moral obligation.” The availability of germline genetic modification would likely trigger powerful competitive dynamics within and between societies. Given the competitive pressures and commercial dynamics of the current social order, where hype often outstrips science, it is all too easy to envision a future in which fertility clinics advertise procedures to “give your child the best start in life,” in which parents feel pressured to “enhance” their children so that they can get into top colleges and jobs, and in which countries feel obligated to “enhance” their populations to compete with other nations.
  7. “Even if only the affluent could afford genetically enhanced children at first, wouldn’t it trickle down to the rest of us before long?”

    CGS: As many proponents of germline enhancement acknowledge, its availability would likely exacerbate existing inequalities, and create new kinds of discrimination.

    Our society is already plagued by dramatic inequalities. Access to new technologies, as well as to premium education and other advantages, is wildly skewed. “Designer children” of the well-off would likely benefit disproportionately from these additional opportunities, whether or not their engineered traits really made them better or smarter. We need to take seriously the potential emergence of a social system of genetic haves and have-nots.
  8. “We already ‘design’ our children by choosing reproductive partners, sending them to private schools, and giving them music lessons. What’s the big deal about germline genetic modification?”

    CGS: Parents rightly have a great deal of control over various aspects of their children’s lives, but pre-selecting their traits is qualitatively different.

    Germline gene editing would give parents (and fertility clinics, researchers, and others) a far different kind of control over children than anyone has ever had. It’s one thing to offer kids opportunities like piano lessons or extra coaching; it’s quite another to force them into a pre-determined biological mold.
  9. “In terms of public policy, would germline genetic modification be okay if it were only be used for medical reasons?”

    CGS: There is no clear boundary between medical and enhancement applications.

    How would we classify short stature, slightly increased risk of obesity or depression, or reduced need for sleep? The inherently blurry nature of the difference between therapy and enhancement would make it impossible to implement a policy on germline gene editing that relied on this distinction.
  10. “Even if there are dire social consequences, isn’t germline genetic modification inevitable?”

    CGS: In democratic societies, people can shape the rules under which they live. 

    Although momentum for germline gene editing could accumulate through social incentives, marketing, and dedicated resources, no technological application is inevitable simply because it is hypothesized. We need broad and inclusive discussions of what we want our future to hold. We can help scientists ensure that their discoveries are used to benefit humanity, for example, to close gaps in health and welfare, instead of widening and exacerbating existing inequality. We need not resign ourselves to unwanted changes imposed by the market, small groups of technological enthusiasts, or anyone else.
  11. “Is criticizing germline gene editing anti-science?”

    CGS: Just the opposite. We can affirm the process of scientific inquiry and its contributions to human well-being, yet understand that not everything that can be done should be done. 

    Discussions of emerging technologies must be placed into social contexts, so that their consequences can be understood, in the short-term and into the future. Societal agreements to put harmful uses of gene editing off-limits will help build public support for responsible science and for its beneficial uses.
  12. “Is germline gene editing already regulated?”

    CGS: Many countries and a multinational international treaty prohibit it. However, the United States has no binding law in place.

    Dozens of countries, including almost all with advanced biomedical sectors, have enacted laws prohibiting the creation of genetically modified people. The Council of Europe’s Convention on Human Rights and Biomedicine, signed and ratified by many European countries, also prohibits it. In the US, the National Institutes of Health and the Food and Drug Administration recently reaffirmed that they will not approve experiments with germline modification for reproduction, but no law explicitly prohibits the creation of genetically modified humans.
  13. “Human embryos have already been modified using CRISPR – isn’t the horse out of the barn?”

    CGS: Non-viable human embryos were CRISPR-ed in April 2015, and a license is pending in the UK.

    The non-viable embryos modified by the Sun Yat-sen University team in April 2015 could not have been used to initiate pregnancies. Further, that experiment was not successful. In September 2015, researchers in London applied for the first-ever license to begin research on embryos left over from IVF. Carefully regulated experiments with human embryos in order to learn about early development can be distinguished from research efforts meant to pave the way for creating genetically modified human children.
  14. “If germline gene editing is safe, doesn’t that resolve the ethical questions it raises?”

    CGS: Safety and accuracy constitute the minimum, not the totality, of concerns.

    While some scientists and others characterize safety as the paramount concern about germline gene editing, most observers recognize a range of momentous social, legal, ethical and economic implications. These include issues related to genetic determinism and biological discrimination; children’s autonomy and selfhood; disability rights; decisions about the allocation of funds and resources devoted to health care and research; and the prospect of reinforcing and exacerbating inequality, discrimination, and conflict.
  15. “Why not let scientists and other technological experts assess the technical safety risks and decide what to do?”

    CGS: Scientists are themselves divided. And this decision is not primarily a scientific one.

    Many of the scientists who developed the new gene editing tools are themselves skeptical about or opposed to using them to create genetically modified people. Others support only a temporary moratorium on using germline gene editing for reproduction, and research aimed at proceeding to clinical trials. The Center for Genetics and Society and many others support research aimed at making gene editing safe in order to medically treat existing people, but urge a prohibition on its use to create genetically modified humans.
  16. “I’m not a scientist. Why should I care about editing human genes?”

    CGS: Some new technologies can dramatically alter our lives and societies. We should choose and shape them democratically.

    New biotechnologies are changing the “facts on the ground” of our lives and societies, and raising crucial questions about how we relate to one another and govern ourselves, and even the essential biology of a human. Yet these powerful tools are often shaped solely by scientists and the companies or institutions where they work, with little public participation or oversight. While scientists can help us understand the technical benefits and risks of their work, we need broad democratic discussion about technological innovations, and about how they can improve well-being and assist us in closing gaps in health and welfare, instead of widening and exacerbating existing inequality.