POLITE NOTICE: this article contains facts about infant nurture which some readers may find distasteful or even offensive. As someone who breast-fed three children on and off over eight years, I know how touchy people can be. Simply by breast-feeding my babies as often as they needed and for as long as we both liked, I managed to cause offence to health visitors, female friends, distant relatives and the occasional stranger.

Before nursing my toddler, Alice, I used to check first if people were OK with it, rather as if I were about to light a cigarette. Passive breast-feeding is clearly a menace to modern society.

Alice stopped feeding at 2½, but some children take it further. Of course, the farther they go, the more society is offended. American and Canadian divorce custody cases have even classed long-term nursing of five-year-olds as a sexual aberration. As Madonna famously remarked when an eight-year-old child was seen to nurse on daytime American TV, “That’s incest.” Yet, believe it or not, throughout history and across the globe, there have always been eight-year-old nurslings. And while their acts of conspicuous consumption may seem to many like defiance or perversion, the truth is that it’s all perfectly within nature’s plan.

Lactation experts agree that human milk is designed to be delivered over years, not months: that it’s not merely food but a source of comfort and wellbeing long after the baby starts to taste solids. “Some children nurse less than two and a half years, and some nurse longer than seven years,” says Katherine Dettwyler, a biocultural anthropologist who since 1981 has researched the question of long-term breast-feeding. Seven seems to be the usual cut-off point. “There is no research,” she adds, “to support a claim that breast-feeding a child at any age is in any way harmful to a child.”

One obvious clue is the comparison between different species. Some animals, such as the guinea pig, are “short-lactating”, ie, their babies are born mature and weaned within a few days. Primates are long-lactating: they wean their babies between one and seven years, depending on their body size. Macaque monkeys, for instance, which are slightly bigger than the domestic cat, nurse for a year or two. Chimpanzees suckle their young for between four and six years. Needless to say, we humans must count ourselves biologically among the primates.

Never mind the government recommendation of six months’ breastfeeding, or that only 21 per cent of British babies actually reach this nursing milestone. Human milk is very low in protein and designed for slow release. Less protein is not a nutritional deficiency, but nature’s way of keeping the human baby as small and portable for as long as possible. (By contrast, cow’s milk is high in protein, enabling calves to double their weight in 50 days.) The point of being carried around is that the big-brained baby has everything to learn and must do so by observing. He drinks in his culture, its people and their language along with his mother’s milk. This milk changes daily — it even goes from low-fat to high-fat mid-feed — and it changes as the years progress. Human milk provides the nutrients for rapid brain growth and hormones for optimum health, with advantages reaching far into adulthood. Although every culture introduces solids by the end of the first year of life (and some start in the first few weeks), breast-feeding provides a long overlap from infancy to independence and many societies are in no wish to hurry the process.

In the early 1900s, Chinese and Japanese children were routinely breast-fed until they reached four or five. Ancient Egyptians nursed for three years and the Inuit people traditionally suckled their children for seven years. In our own history, 19th-century mothers in East Lincolnshire (for instance) nursed their children for seven or eight years each. Today, Asia is the place where babies are most likely to be nursed long-term. In Bangladesh, one of the world’s poorest countries,

90 per cent of two-year-olds are still nursing; the figure in Nepal is 88 per cent. Our own Infant Feeding Survey stops counting at nine months, when it records that just 13 per cent of babies are still breast-fed, but even this implies about 70,000 nursing mums. I know of mothers who have quietly continued with night-time feeds after their children have started school, but it’s not something many of them would advertise.

Breast-feeding is usually a discreet experience. A new baby suckles quietly, his head swathed in a baggy jumper or shawl, and it’s rare to sight a nipple, let alone bare skin. But nursing toddlers is more messy. Their heads turn this way and that in eager curiosity. They talk about “num num” or “mummy juice” and pull at your T-shirt when you’re shaking hands with the head teacher. At 17 months, my third child, Joe, would wriggle around like a jumping bean, suddenly leaping off my lap mid-feed and leaving me exposed to view. Seconds later, he would jump back on again. Not surprising, perhaps, that one friend said: “I’m not against breast-feeding, I just can’t bear to see it.” Not surprising, either, that 17 months was all the nursing Joe received.

Despite social prejudice and fretful headlines, most long-term breast-feeding mothers are not sexual deviants, exhibitionists, militants or even overbearing. Not one of them started out with a plan to breast-feed right up to the school gates. The ones who do are usually just those who, prepared to go with the flow, found that the flow lasted longer than expected. They carry on to the uncomfortable point where biology is crushed by cultural prejudice.

And on that subject, a special mention must go to Richard Page, the Conservative MP for Hertfordshire South West, who, when approached recently for his support by breast-feeding mothers, remarked: “I do not believe that breast-feeding in public is acceptable or indeed necessary. There were one or two Labour MPs who tried to argue that breast-feeding should be allowed in the chamber of the House of Commons, and thank heavens that was promptly squashed.”

This sort of bigotry is perhaps the greatest obstacle to improving breast-feeding rates in our country. When society finds the nurturing act itself revolting, a mother’s primary emotions are guilt and embarrassment and she is more likely to retreat underground if she continues at all. It is not necessary to promote long-term breast-feeding as an end in itself. But as long as we remain squeamish about the breast’s real function, confusing childcare and babycare with sex, mothers will find it hard to be accepted for doing their best. In such a climate, it becomes almost impossible to accept the mother who wants to continue breast-feeding for as long as she likes.

See www.thewaynatureintended.org for the campaign to promote the rights of mothers to breast-feed in public