By ELIZABETH FARRELLY
News of a brat gene will surprise few parents: not me, probably not you, certainly not Eva Khatchadourian who, in We Need to Talk About Kevin, gives birth to the devil.
The gene, identified by Arizona scientists and catchily named SLC6A4, is thought to encourage ''non-compliant'' behaviour and I, for one, am persuaded. In fact I reckon I've got one. At least one. Perhaps even two, if you can imagine a brat gene being recessive.
But, contrarian as I am, I'm a mild and harmless case. I'm Johnson's no more tears baby shampoo compared with the two children adopted almost 20 years ago by a friend of a friend, call her Judith, now in her 60s. Hers were the last two from parents whose other 10 had been forcibly removed and she got them young - six months and 24 months.
In parenting terms, Judith did everything right - love, education, authority. Yet now, in their late teens, the kids lie, cheat and steal, even from her. They are consistently mean, ungiving and unhelpful towards the woman who sacrificed so much for them. What does it signify if not what our Victorian forebears would have called ''bad seed''?
This, of course, is what Sandra Auchterlonie meant by the ''evil Milat gene'' that killed her grandson David on his 17th birthday, a year ago last weekend. It sounds like the ranting of grief. And true, the unnamed Milat relative could have been influenced by family as much as genes.
But it's possible. If there's a brat gene, there could easily be a mass-murderer gene. And if such a gene were identified, what would we do about it? Would we scan for it in the womb? Cull the embryo? Would there be a rush back to eugenics?
This is an idea we resist, for obvious reasons. If we're culling this gene, what about that one? But this repugnance makes us resist, perhaps wrongly, the very idea of genetic links to personality.
We have no difficulty seeing such links in other species. No problem linking genes to temperament in horses or dogs. No issue understanding that a pitbull will likely have a different personality from a golden retriever. No demurral from breeding selectively this way or that.
But humans we regard as special. And it's those who most vehemently oppose eugenics, the left, who also most vehemently insist that humans are just another animal species. Indeed, this is the most fascinating thing about the otherwise exhausted nature-nurture argument: how politicised it has become, and why.
The left, to have any agenda at all, must believe humans are not only redeemable but essentially born equal. Born blank. Feminism, multiculturalism and all other forms of equalism are similarly tied to the essential equality of genders, races (and even species), making nurture everything. The right, by contrast, is wedded to a natural hierarchy; a God-given pecking order that, even without aristocratic overlay, has us sorted from birth.
Me, I'm a quid each way. I'm not naturally a grey-scale person, being more inclined to contrast than nuance. (Could this be the aesthetic phenotype of that brat gene?) But on nature-nurture I'm definitely both. And increasingly, it seems, science is with me. Even those Arizona scientists found that one effect of the brat gene was to increase the child's vulnerability to bad parenting. Bad mothering, to be precise.
This obviously raises the question: how would they know that? How does anyone know what the kid would have been like with good parenting? And further, how do they define good parenting, if not by the behaviour that results?
(''Good'' mothering, in case you're wondering, was assessed annually by observers during three-minute play and puzzle periods on criteria including sensitivity, intrusiveness and maternal warmth. Nothing like an observation room to bring out maternal warmth.)
Still, it seems intuitively right that both nature and nurture are implicated. The gene gives a tendency that environment either dampens or amplifies. But what is the balance, and what are the implications for changing - OK, improving - human behaviour?
This is the subtext to We Need to Talk About Kevin. Billed as psycho-horror, the gory story of a teenage teen-killer, it is really a disquisition on responsibility, truth and genetics. In Lionel Shriver's novel, Eva tells her story in a series of letters to her dead husband. She has no reason to lie or even gloss. It is the story of how the child, Kevin, gradually destroys everything she has ever valued; wealth, work, reputation, family and love.
She had been ambivalent about the pregnancy, unmoved by the birth and depressed after. These things do not usually produce bloodbaths. She cannot tell how much of her own view is subjective - how much of her revulsion is from the baby's glinting evil - and nor can we. The book could read as a study in the impossibility of manufacturing love at will, and of child-rearing without it.
No doubt Eva contributes something - coldness, distance - to the terrible denouement. Certainly she feels culpable and spends her subsequent years seeking punishment. But the driving evil is clearly Kevin's.
Even as a newborn he hates her, hates everyone, hates being in the world, and his crimes - the blinding of his six-year-old sister is hardest to read - are a finely tuned revenge on his mother for bringing him into it.
The book leaves you in no doubt that Eva, had she been prophetic, would have aborted him. But would we, as a society? Should we?
''You know me, you know my family … I did what they do. At one stage the axe got stuck, so I had to kick the back of his head to get it loose.'' Like Kevin, the anonymous Milat murderer recalls an unpalatable truth: some people are, simply, evil.
But you tell me. If this were shown to be genetic, if ''bad seed'' were once again a thinkable thought, would we kill, cull, imprison, medicate or genetically engineer (as the bioethicist Julian Savulescu recommends) to pre-empt it? Or would the presumption of innocence so lost be too much to pay for the lives so saved?
And there's this: who decides? Certainly I'd fight to keep my brat gene from the serried ranks of teachers and bosses who would have plucked it from me.