率直な問い
'Designer babies' usually means choosing a child's intelligence, height, appearance or athletic ability. The ethical debate is serious, but it runs far ahead of the biology: traits like intelligence and height involve thousands of genetic variants each contributing a tiny amount, interacting with environment in ways nobody can predict. There is no gene to edit for these things. The realistic near-term question is narrower and more uncomfortable — the boundary between preventing disease and choosing preferences.
Enhancement editing would target traits rather than pathology. Polygenic architecture makes most desired traits inaccessible to editing: educational attainment and height involve thousands of variants of individually minute effect, with substantial gene-environment interaction and pleiotropy. Even were germline editing safe, the technical premise of trait selection by editing is largely unsupported. The practically pressing question is where disease prevention ends — deafness, achondroplasia and autism are each understood very differently by different communities.
The arguments
- Parents already shape children's traits through education, nutrition, medicine and environment; genetic means are not obviously different in kind.
- A firm line between therapy and enhancement is hard to draw — vaccination enhances immunity beyond the natural baseline and is uncontroversial.
- If a safe intervention reduced the risk of a serious late-life disease, refusing it on principle may be harder to defend than permitting it.
- The polygenic reality means promised enhancements are largely unachievable, so the debate risks legitimising claims that cannot be delivered.
- Selecting traits imposes one generation's preferences on people who cannot object.
- Access would follow wealth, and heritable advantage compounds in a way no other inequality does.
- Defining some human variations as defects to be edited out is a judgement disabled communities have consistently and forcefully rejected.
- Pleiotropy means editing for one trait may alter others unpredictably — the same variants often do several things at once.
Where the science actually stands
Complex traits are highly polygenic. Predicting the effect of editing a small number of variants on intelligence, personality or physical performance is not currently possible, and no evidence indicates otherwise. Debate about enhancement is therefore about a capability that does not exist — which does not make the debate pointless, but does mean claims of imminent capability should be treated sceptically.
Unresolved questions
- Where disease ends and preference begins, in conditions that communities themselves define differently.
- Whether prohibitions could hold if the capability ever became real.
- How to weigh reducing suffering against reducing human variation.
Sources
- National Academies of Sciences, Engineering, and Medicine · 2020
Heritable Human Genome Editing ↗ - World Health Organization · 2021
WHO issues new recommendations on human genome editing for the advancement of public health ↗