Rewriting Life: The Ethics of Gene Editing

In 2012, the biochemists Jennifer Doudna and Emmanuelle Charpentier published a paper describing how a bacterial defence mechanism, known as CRISPR-Cas9, could be repurposed to cut DNA at precisely chosen locations. Eight years later, they were awarded the Nobel Prize in Chemistry. Rarely has a scientific breakthrough moved so swiftly from obscure laboratory technique to a tool with the capacity to reshape medicine, agriculture and, conceivably, humanity itself.

The therapeutic potential is difficult to overstate. In 2023, regulators in the United Kingdom and the United States approved the first CRISPR-based treatment for sickle cell disease, a painful and debilitating inherited blood disorder that is relatively prevalent in parts of Africa, the Middle East and South Asia. For patients who previously faced a lifetime of crises and hospital admissions, the treatment offers the prospect of something close to a functional cure.

Researchers are also investigating applications in cancer, inherited blindness and certain forms of high cholesterol, while agricultural scientists are developing crops engineered to withstand drought — a prospect of considerable significance for arid regions.

Ethicists draw a crucial distinction between somatic editing, which alters the cells of an individual patient, and germline editing, which modifies embryos, eggs or sperm. Changes of the latter kind would be inherited by all subsequent generations, and their long-term consequences are, by definition, impossible to observe in advance.

That distinction ceased to be hypothetical in 2018, when a Chinese researcher announced the birth of twin girls whose embryos he had edited in an attempt to confer resistance to HIV. The announcement provoked near-universal condemnation from the scientific community — not least because the procedure was medically unnecessary, conducted without adequate oversight and of dubious efficacy. The researcher was subsequently imprisoned.

Beyond questions of safety lie thornier philosophical concerns. If it becomes possible to eliminate devastating diseases from a family line, few would object. But the boundary between therapy and enhancement is notoriously porous. Should parents be permitted to select for height, athletic ability or intelligence, insofar as such traits are genetically influenced at all? Critics warn of a new form of inequality in which the wealthy purchase biological advantages for their children, while disability-rights advocates question the implicit judgement that certain lives are less worth living.

Proponents counter that refusing to use a technology capable of alleviating immense suffering is itself an ethical choice, and not necessarily a defensible one.

There is, as yet, no binding international consensus. Many countries prohibit heritable genome editing outright, while international bodies have called for a robust global framework before any clinical use is contemplated. What seems indisputable is that decisions of such magnitude cannot be left to scientists alone. The question of which kinds of human beings we wish to bring into existence is, ultimately, one for society as a whole.