I think Gregory Stock has misunderstood a couple of the points I was trying to make in my initial response. The issue with regard to sex selection is not that it would be a serious problem in this country; it's possible now, after all, but not widely practiced. The point is that individual choice coupled with the spread of cheap biomedical technologies can quickly produce population-level effects with serious social consequences. In other words, the problem with eugenics is not simply that it is state-sponsored and coercive; if practiced by enough individuals, it can also have negative consequences for the broader society.

I suspect that if the U.S. ever gets into something like this in the future, it will have to do with potential "enhancement" targets other than sex. One I speculate about in my book is sexual preference: It seems pretty clear to me that if parents, including ones who are perfectly accepting of gays today, had the choice, they would select against their children being gay, if for no other reason than their desire to have grandchildren (contrary to Stock, by the way, gays can't reproduce, so I'm not quite sure how they'd do germline intervention to produce gay children). The proportion of gays in the population could drop quite dramatically, and I'm not at all sure that society as a whole (let alone gays as a persecuted minority) would be enhanced as a result.

Governments can intervene successfully to correct individual choices like these. The severe sex ratio imbalance in Korea that emerged in the early 1990s was noticed, and the government took measures to enforce existing laws against sex selection so that today the ratio is much closer to 50-50. If the government of a young democracy like Korea can do this, I don't see why we can't.

The reason I noted that life extension coupled with diminished capability can create negative externalities was not to suggest that we should ban or regulate such procedures. Stock is perfectly right that we already have adopted a lot of medical innovations that produce this tradeoff, and that we can't stop future advances for this reason. The reason this is an important issue is that in contemporary debates over stem cells and cloning there is an unquestioned assumption that anything that will prolong life or cure disease is obviously desirable and automatically trumps other ethical concerns.

This is not obvious to me. Anyone who has walked around a nursing home recently (as I have) can see that past advances in biomedicine have created a horrible situation for many elderly people who can't function at anything close to the levels they'd like, but who also can't die. Of course, new advances in biotechnology may provide cures for degenerative, age-related diseases such as Alzheimer's or Parkinson's, but the research community is in effect just cleaning up the mess it created. So when we are balancing near-term rights and wrongs, the argument that more medical advance is necessarily good needs to be treated with some skepticism. At the hearing on the Weldon bill banning cloning last summer, a representative of a patients advocacy group said the baby boomers were getting older and desperately needed cures for a variety of diseases with which they would soon be afflicted-as if research cloning would prevent them from ever having to die. If you want a real nightmare scenario, consider one in which we double life spans but increase periods of debility by a few decades.

Stock is correct in saying that much of my interest in having new regulatory institutions in place has to do with ethical and social consequences of new technology, and not simply safety. States intervene all the time to shape norms and produce certain social outcomes. Incest is an example, and it seems to me a very apt analogy to reproductive cloning. Of course, you can find sympathetic situations where an individual might want to clone, say, a dead child. But you can also find sympathetic situations where you might want a brother and sister to marry and have children (e.g., they have grown up apart, have no dangerous recessive genes, etc.).

But the fact that there are certain sympathetic cases does not mean that society would be better off without a ban on incest. The possible benefits of cloning need to be balanced against social harms. Consider the following scenario: A wife decides to clone herself because a couple cannot otherwise have children. As their daughter grows up to be a teenager, the husband will find his wife growing older and less sexually attractive. In the meantime, his daughter, who will be a physical duplicate of her mother, will blossom into sexual maturity and increasingly come to resemble the younger woman the husband fell in love with and married. It is hard to see how this situation would not produce an extremely unhealthy situation within the family; in a certain number of cases, it would lead to incest.

Stock is using a rhetorical ploy in suggesting that I am recommending new, tyrannical government intrusion into private lives. Rather, I am recommending an extension of existing institutions to take account of the new possibilities that will be put before us as a result of technological advance. This may result in regulation irksome to industry and to certain individuals, but it will be no more tyrannical than existing rules banning incest or, in the case of the Koreans, banning sex selection. All societies control social behavior through a complex web of norms, economic incentives, and laws. All I am suggesting is that the law part of the mix will need to be updated and strengthened in light of what is to come.