Devastated mothers send me confiding letters detailing horror stories of offspring just like the wicked boy in my book. Women who'd declined to have children flock to my readings, raising the novel as proof they were right.

Childless at 48, I'm now old enough for the question of motherhood to have become merely philosophical. Still, I've had all the time in the world to have babies. I am married. I've been in perfect reproductive health. I could have afforded children, financially. I just didn't want them. They are untidy; they would have messed up my flat. In the main, they are ungrateful. They would have siphoned too much time away from the writing of my precious books.

Nevertheless, after talking myself blue about "maternal ambivalence", I have come full circle, rounding on the advice to do as I say, not as I did. I may not, for my own evil purposes, regret giving motherhood a miss, but I've had it with being the Anti-Mom, and would like to hand the part to someone else.

Allusion to Europe's "ageing population" in the news is now commonplace. We have more and more old people, and a dwindling number of young people to support them. Not only healthcare and pension systems but the working young will soon be overtaxed, just to keep doddering crusties like me alive. Politicians sensibly cite age structure when justifying higher rates of immigration, and not only because Europeans so fancy themselves that they refuse to clean toilets. Even if the job appealed, there are already too few of the native-born of working age to clean all those toilets.

I propose that we have now experienced a second demographic transition. Rather than economics, the engine driving Europe's "birth dearth" is existential.

To be almost ridiculously sweeping: baby boomers and their offspring have shifted emphasis from the communal to the individual, from the future to the present, from virtue to personal satisfaction. Increasingly secular, we pledge allegiance to lower-case gods of our private devising. We are less concerned with leading a good life than the good life. We are less likely than our predecessors to ask ourselves whether we serve a greater social purpose; we are more likely to ask if we are happy. We shun values such as self-sacrifice and duty as the pitfalls of suckers. We give little thought to the perpetuation of lineage, culture or nation; we take our heritage for granted. We are ahistorical. We measure the value of our lives within the brackets of our own births and deaths, and don't especially care what happens once we're dead. As we age - oh, so reluctantly! - we are apt to look back on our pasts and ask not 'Did I serve family, God and country?' but 'Did I ever get to Cuba, or run a marathon? Did I take up landscape painting? Was I fat?' We will assess the success of our lives in accordance not with whether they were righteous, but with whether they were interesting and fun.

The question is whether kids will make us happy.

However rewarding at times, raising children can be also hard, trying and dull, inevitably ensnaring us in those sucker-values of self-sacrifice and duty. The odds of children making you happier are surely no better than 50-50. A few years ago the New York Times published the results of a study that found the self-reported "happiness" index was lower among parents than the childless. Little wonder that so many women have taken a hard look at all those nappies, play groups, nasty plastic toys and said no thanks.

Not to disparage old people, but "senescent" is not a pretty word. Large sectors of western population have broken faith with the future. In the Middle East, birth rates are still sky-high, whereas Europeans, Australians and many European-Americans cannot be bothered to scrounge up another generation of even the same size, because children might not always be interesting and fun, because they might not make us happy, because some days they're a pain in the bum. When Islamic fundamentalists accuse the west of being decadent, degenerate and debauched, you have to wonder if maybe they've got a point.

When I press her on the implications of a contracting European population, she readily concurs that "many western cities will be largely black/ Hispanic/Asian in 50 years' time. Does that bother me? Well, I vaguely regret the extinction of gene lines that in their various ways played a part in the establishment of western civilisation. But the gene lines coming in from the developing world will have their own strengths, energies and qualities."