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Human genetic modification (or “gene editing”) can be used in two very different ways. Somatic genome editing changes the genes in a patient’s cells to treat a medical condition. A few gene therapies are approaching clinical use but remain extraordinarily expensive.
By contrast, heritable genome editing would change genes in eggs, sperm, or early embryos to try to control the traits of a future child. Such alterations would affect every cell of the resulting person and all subsequent generations.
For safety, ethical, and social reasons, heritable genome editing is widely considered unacceptable. It is prohibited in 70 countries and by a binding international treaty. Nevertheless, in 2018 one scientist announced the birth of twins whose embryos he had edited. This reckless experiment intensified debate between advocates of heritable genome editing and those concerned it could exacerbate inequality and lead to a new, market-based eugenics.
Genetic testing also harbors the potential for yet another scientific strategy to be applied in the area of eugenics, or the social philosophy of promoting the improvement of inherited human traits through intervention. In the past, eugenics was used to justify practices including involuntary sterilization and euthanasia. Today, many people fear that preimplantation genetic diagnosis may be perfected and could technically be applied to select specific nondisease traits (rather than eliminate severe disease, as it is currently used) in implanted embryos, thus amounting to a form of eugenics. In the media, this possibility has been sensationalized and is frequently referred to as creation of so-called "designer babies," an expression that has even been included in the Oxford English Dictionary. Although possible, this genetic technology has not yet been implemented; nonetheless, it continues to bring up many heated ethical issues.
Trait selection and enhancement in embryos raises moral issues involving both individuals and society. First, does selecting for particular traits pose health risks that would not have existed otherwise? The safety of the procedures used for preimplantation genetic diagnosis is currently under investigation, and because this is a relatively new form of reproductive technology, there is by nature a lack of long-term data and adequate numbers of research subjects. Still, one safety concern often raised involves the fact that most genes have more than one effect. For example, in the late 1990s, scientists discovered a gene that is linked to memory (Tang et al., 1999). Modifying this gene in mice greatly improved learning and memory, but it also caused increased sensitivity to pain (Wei et al., 2001), which is obviously not a desirable trait. Beyond questions of safety, issues of individual liberties also arise. For instance, should parents be allowed to manipulate the genes of their children to select for certain traits when the children themselves cannot give consent? Suppose a mother and father select an embryo based on its supposed genetic predisposition to musicality, but the child grows up to dislike music. Will this alter the way the child feels about its parents, and vice versa? Finally, in terms of society, it is not feasible for everyone to have access to this type of expensive technology. Thus, perhaps only the most privileged members of society will be able to have "designer children" that possess greater intelligence or physical attractiveness. This may create a genetic aristocracy and lead to new forms of inequality.
At present, these questions and conjectures are purely hypothetical, because the technology needed for trait selection is not yet available. In fact, such technology may be impossible, considering that most traits are complex and involve numerous genes. Still, contemplation of these and other issues related to genetic engineering is important should the ability to create genetically enhanced humans ever arise.
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