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Genetic modification of characteristic masculine traits: enhancement or deformity?
  1. Jeff McMahan
  1. Correspondence to Professor Jeff McMahan, Department of Philosophy, 106 Somerset Street, 5th floor, Rutgers, New Brunswick, NJ 08901, USA; McMahan{at}

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Some philosophers, most notably Julian Savulescu, have argued that potential parents have a moral reason to do what they can to have a child with the highest expected level of well-being.1 This is not just a reason to do what will make a particular child better off than he or she would otherwise be but also a reason to choose, from among different possible children, the one that has the highest expected well-being. The claim that potential parents have such a reason is then often deployed as a premise in arguments in support of genetic enhancement. Robert Sparrow has argued in response that this claim implies that potential parents have a reason to choose to have female children only, primarily because women are genetically disposed to live, on average, 3–7 years longer than men.2 He takes this implication to be a reductio of this particular form of argument in support of human enhancement. In her paper, Sexual dimorphism and human enhancement, Paula Casal seeks to rebut Sparrow's argument and then goes on to suggest that a better case for the selection of female children could be made on grounds of moral enhancement, since women are far less genetically disposed to be violent and aggressive than men.3 Recognising, however, that the creation of only female children would lead to human extinction, she concludes that the way to achieve the best outcome would be to use techniques of genetic modification, should they become available, to make men more like women in certain respects: smaller, less aggressive, less competitive, less violent, less obsessed with sex, less prone to taking great risks, and less likely to die early from accident, combat, or disease.

Like Larry Temkin, I am largely in agreement with Casal on these matters. In this short commentary, I …

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  • Competing interests None.

  • Provenance and peer review Commissioned; internally peer reviewed.

  • i How we can avoid the Repugnant Conclusion. Derek Parfit's unpublished lecture. Available on request from the author.

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