Enough: genetic engineering and the end of human nature by Bill McKibben

If you are worried about the consequences of the biotech revolution, you will welcome Bill McKibben's effort to determine the social and ethical limits, the "enough point", beyond which the technologies of genetic modification and nano-engineering should not pass. At stake, in his view, is humanity's unique capacity for conscious reasoning and moral betterment, and with it our ability to stretch for, and equally to restrain, our desires. What is today in jeopardy is precisely that right which the biotech zealots invoke to legitimise their work: the right to individual freedom.

Human genetic engineering will be an assault on human liberty because it violates the open future of the new-born child. McKibben concedes that all parents exert an influence on the development of their children, but this normally accommodates the child's right to rebel. In contrast, "the engineered child won't have the same ability to walk away from you. If you get the proteins right, it may never occur to him to do so".

McKibben envisages a 16-year-old girl unsure whether her joy arises from the boy she has fallen in love with or the happiness-enhancing DNA she inherited as an engineered embryo. She may also be unable to claim this spirit of questioning, since she may be endowed with a custom-elevated IQ. There is something frighteningly irrevocable about human genetic enhancement, for any dissenting judgements from those with manipulated cognitive powers will always be of suspect moral status.

In arguing for the self-limiting of biotechnology, McKibben gives salutary examples of cultures which have renounced specific technologies without harming their development. Drawing up his own moral Rubicon, McKibben offers a guarded "yes" to somatic gene therapy, pre-implantation genetic diagnosis, therapeutic cloning and the limited use of nano-engineering. But he says "enough" when it comes to modifying the human germline, gestating human clones, conquering our mortality, and self-replicating nano-machines.

Though thoughtful and humane, the arguments of this book are not always convincing. One problem is the author's tendency to swallow the more fanciful claims of biotechnology enthusiasts and pander to an extreme form of genetic determinism. McKibben offers a sobering insight into the opinionated and socially naïve mind of James Watson, demonstrating that being a brilliant biologist does not make you a reasonable or sensitive person. Yet while exposing the flawed attitudes of one scientist, McKibben relies on the private opinion of another - a researcher who assures him that we can "engineer higher intelligence" and "increased athletic ability" - as his ultimate proof that "this new world can't be wished away".

Many other scientists believe our capacity to identify and manipulate the genetic foundations of thoughts and behaviours has been grossly exaggerated. The real danger is that creating children as predetermined products will invite parents to exert inordinate control over the environment in which they are reared. Would you pay for the genes of an Olympic athlete, then allow your creation to pursue an interest in music or books? Indeed, if McKibben's confidence in biological determinism were valid, many of his arguments would be weakened. In this case, there is no reason why your 16-year-old daughter shouldn't already attribute her joyful feelings to hormonal changes, the accidents of heredity, or forces of natural selection.

The pressing danger is not that humanity will eliminate the biological substrates of human experience, but that it thinks this experience can be reduced to a mechanical, and manipulable, cause. Unfortunately, this thought is already with us, as is the thought that parents have the right to predetermine the future of their children, and companies the right to take apart environments and communities in order to sell them back as commodities. When McKibben extols the dignity of paid work in preference to its technological abolition, you may wonder whether his determination to say "enough" leads him towards a political quietism that is a little too accepting of the status quo.

Finn Bowring is the author of 'Science, Seeds and Cyborgs' (Verso)