About 60 strangers gathered in a graveyard in Limerick last Wednesday for the funeral of an unknown baby boy. Named Aidan after the saint on whose feast day he was buried, the child's body had been discovered in a plastic bag on a rubbish skip a month earlier. Last Wednesday he found a more dignified resting place than that chosen by the person who dumped his corpse. A garda sergeant's gloved hands carried the boy's coffin to his grave in the Calvary cemetery after a mass had been said for him in the chapel of a nearby hospital.

There was much concern expressed for his mother by the mourners, who were themselves mostly parents from the local area. They prayed for her health and for her peace of mind. Although it appeared that the baby had not lived to draw a breath, there is no knowing whether the full-term child might have survived if he'd had proper assistance. Indications that the baby had been born in secret, without medical intervention, inevitably prompted questions about why such tragedies still have to happen. There is, after all, scarcely any stigma attached to unmarried motherhood any more and, however controversial it might be, there is still reasonable state and social support for women in that situation. It is difficult to imagine any circumstances in which the only apparent solution to an unwanted pregnancy is to give birth in secret and then dump the child's body on a skip. And as one of the mourners remarked, there are lots of childless couples in the city of Co Limerick who would gladly have given the baby a loving home.

In recent years, adoption has become the least popular option for single young women who find themselves with an unplanned pregnancy. Either they choose abortion, at a rate of about 20 a day, or else they decide to keep their babies and raise them as lone parents. The days when Irish children were available in sufficient numbers to meet the demands of domestic adoptive parents are long gone. Once a single girl has openly carried a baby to term, she is supported and encouraged to keep her child, and it has come to be seen as inhumane, outdated and discriminatory to suggest this may not always be the child's best start in life. Moreover, it is considered bigoted and backward-looking to hold the view that the young woman, also, might be better off without the huge responsibility of a child's care before her own life has even begun.

We have come to embrace alternative family models as a yardstick of our modernity, so that it has become positively primeval to hint that a family unit consisting of two parents, preferably one of each sex, is still the optimal environment for a child's development. We are far too broad-minded these days to acknowledge that children might actually benefit from having both a mother and a father in their life. Instead, the alternatives are championed and celebrated so enthusiastically that the idea of giving your child away to a couple who really want a baby is no longer seen as a valid option for a pregnant, distressed young girl. If it was, perhaps we wouldn't be burying several baby Aidans, those unclaimed little souls who turn up with depressing regularity in our rubbish bins and ditches every year.

In a way, the adoption story that hit the papers last week, revealing that three homosexual Irish couples had applied to adopt, was something of a red herring. If it was expected to create a scare about innocent Irish babies falling into perverted hands, then it was a non-starter. A same-sex couple haven't a hope of adopting an Irish child because priority, for the handful available annually, is still accorded to carefully vetted, securely married and profoundly heterosexual pairs. Nor is there any new market in foreign waifs being supplied with impunity to anybody who asks: single people have been able to adopt in this country for some time now, and there is nothing in the legislation to state that they are ineligible if they happen to be gay.

What is new is that the gay couples are seeking to adopt as couples, not as single people with partners who may subsequently apply for guardianship rights. It is an indirect bid to have the validity of their relationships recognised in law, in circumstances where the status of legal, foreign gay marriages is still a grey area. It puts our contemporary definitions of a family unit under the spotlight.

"Oh, a family is people and a family is love, that's a familee," Barney the dinosaur sings incessantly from my toddler's favourite video. "They come in all different sizes and different kinds, and mine's just right for meee." It's hard to argue with the purple chap on this matter. There are a great many single parents, male and female, bringing up their children in an exemplary fashion. Some child psychologists now suggest that children are better off in a calm and stable single-parent household than living amid the hostility of warring couples who stay together solely for the sake of the offspring. There are lots of grandparents taking care of the youngsters of their own immature, ill or awol children, and making a great job of it. And there are undoubtedly many homosexuals who have children and who love and care for them no less than their straight counterparts. If it is the case that gay couples are to adopt children and raise them in a same-sex household, then it is fair to assume they will have to meet all the standards and cross all the hurdles that heterosexual couples would face in the same circumstances.

A child's natural, heterosexual parents aren't always guaranteed to provide the best and happiest home life — those three little children effectively orphaned when their mother was battered to death and their father arrested for her murder in Spain last week are only the most recent proof of that. And a handsome, well-heeled, happily married straight couple aren't necessarily the best adoptive parents an impoverished lone woman could wish for her child — just look at the recent pictures of little Tristan Dowse after he was returned to his Indonesian orphanage.

We can all cite examples of contented, stable but irregular family units, just as the textbook family model often turns out to be a horror story rather than a fairy tale. But that shouldn't stop us being able to say that the best and most desirable type of family, where the interests of children are at stake, comprises a happily married heterosexual couple. However secure and established a same-sex couple may be, and however solidly legal their marriage is in the eyes of their state, they simply cannot provide a child with the same social and emotional environment as a mixed household. Men and women may not be from different planets, but they are very different creatures and they bring different strengths, gifts and insights to their relationship with their kids.

Just because some children may be better off being raised without the influence of an aggressive father or an alcoholic mother in their lives, it doesn't follow that they don't really need two committed, loving parents. We already accept that single women can be excellent parents. We should be free to acknowledge that a happy, united and responsible gay couple could make great parents, so long as we are not therefore prohibited from holding, as a basic principle, that a happy, united and responsible heterosexual pair would probably make an even better mum and dad.