Nature 452, 665-666 (10 April 2008) | doi:10.1038/452665b; Published online 9 April 2008

Defining 'natural'


Visceral reactions to an act should not distract from the real ethical issues.

From an evolutionary perspective, we humans have good reason to be wary of things that seem to be 'unnatural'. Anything out of the ordinary can be dangerous. But the evolutionary origin of that response also guarantees that it will be guided more by emotion than by reason. Witness the reaction last week when Thomas Beatie, from Bend, Oregon, announced his pregnancy on the popular television talk show, Oprah.

Beatie, who was born female (and participated in beauty pageants), underwent hormone treatment and some gender-reassignment surgery ten years ago, but retained his reproductive organs. He stopped taking hormones so that he and his wife, who cannot bear children, could pursue artificial insemination. Several doctors turned them down, but last week, the world watched as a baby-faced man with a thin beard and a growing paunch went for an ultrasound: the fetus was a girl. Oprah Winfrey was supportive as she nursed the nervous Beatie through a discussion of his personal realizations. So was the lesbian, gay, bisexual and transgender community. But other reactions were vitriolic, as when MSNBC's Joe Scarborough repeatedly commented that he was "going to be sick". Other such visceral responses were common on message boards and blogs on the Internet, where the situation was often held to be disgusting and unnatural.

And yet, when we consider this story with the reasoning parts of our brains, exactly what was so 'unnatural'? The longing to have a baby? That is a profoundly human desire, whether the prospective parents are male, female or transgendered. Or is it that Beatie has acted on his certainty that he is a man who happened to be born without a Y chromosome? Biologists have found that gender-straddling and gender-switching behaviours are not at all uncommon in the 'natural' world, either for humans or non-human animals (see page 678). True, modern biotechnology has considerably raised the stakes, and is allowing humans to manipulate their biological make-up to an ever-increasing degree. But it hasn't fundamentally changed the game. And its applications, however unsettling they may be to some people, are not, by definition, 'unnatural'.

This same question of 'natural' versus 'unnatural' also emerges this week in a very different context: an online poll that Nature started in January on the use of neuroenhancing drugs (see page 674). Respondents were asked to report on their non-medical use of drugs such as modafinil and methylphenidate to improve their concentration. These drugs can have mild effects, not all that different from caffeine (a natural substance) or other stimulants. But somehow the 'unnaturalness' of these drugs makes some people uneasy in a way that caffeine does not. The claim, repeated in many responses to our survey is that using such drugs, or any performance-enhancing drug, makes accomplishments somehow less worthy because they aren't natural. But again, what is 'natural'? Devices such as glasses, hearing aids, pacemakers and artificial hips are unnatural. Yet they are widely accepted as legitimate ways to enhance the human experience. By the same token, if drugs enhance performance on a standardized test, what is so 'natural' about prep courses designed to improve scores?

Ultimately, our visceral concept of what is 'natural' depends on what we are used to, and will continue to evolve as technology does. But in the meantime, we should not allow it to distract us from the rational consideration of deeper and more important ethical issues. In the case of Beatie and his wife, the elemental questions are the health, safety and emotional security of the child. Trying to decide such issues simply by fixating on a fluid and arbitrary definition is, by nature, silly.