God, oh God, something like a quarter of the world still lacks access to running water, basic medical care, and 2000 calories a day. So in the scheme of things, the passage of the NSW adoption Bill 46-44, is a small matter.

Yet, on the other hand of course, it isn’t. It represents an enormous change in our understanding of what rules and conditions society should set. Furthermore, it’s an issue that’s not easily compared or assimilated to others.

Legalisation of homosexuality, equal financial, legal, etc, status for same-sex partners, etc, — these days no one, save for religiously based conservatives could have any objection to these. And the vast majority of liberal-minded people believe that the issue of adoption and child-raising can be assimilated to this larger question.

The trouble is that really, the issue isn’t and can’t be constructed as a mere extension of consenting rights. Fundamental questions have to be asked about a fairly dramatic socio-legal change — and reflection on that would, I suggest, lead one to conclude that same-sex adoption — specifically male-couple adoption — should not be legalised.

Typically, pro and con sides of the debate square off over complementarity. A child, they argue, is better off with a mother and father. The stronger version is that a child has a right to a mother and father, a right grounded in biology.

The pro-faction disputes any evidence that a biological couple, or an adoptive replica of one, provide better outcomes, and tend to take a “social constructionist” view — that same-sex parenting is a liberation of general parts of life — love, care, discipline, etc — that were hitherto assumed to be either masculine or feminine in purview.

Both the “rights” argument and the “social constructionist” one are full of merconium.

To take the “rights” one first. You have to be seriously ignorant to think that the biological couple is the standard unit of parenting. Pre-cultural humans appear to have lived in multifamily bands, and the “parental unit” in many traditional “kinship” societies usually consisted of a woman and her maternal brother.

Ancient societies overwhelmingly turned child-raising over to groups of women, and feudal and early-modern (i.e. post-1400) societies tended to exchange children between mothers and grandmothers, sisters and cousins, convents and other institutions, with great fluidity, until the state took over the adoption process in the 19th century. And there are a few societies in which the concept of a father more or less has no meaning altogether.

That variety of child-raising possibilities led some to argue that parenthood itself is purely a social construction. But that’s where the social constructionist model runs out, for the idea of complementarity leads some to assume a type of equality between the roles of father and mother, which isn’t the case. They’re obviously asymmetrical. The father is overwhelmingly a culture role, the mother — and the mother-child bond — is one that lies on the boundary between culture and biology.

That shouldn’t be necessary to point out, but the times dictate that it is. We’re a biological species, with an unusual degree of infant dependency, and species reproduction has depended on the sustained bond of a feeding mother and infant. It would be bloody unusual if an infant were not oriented to the female body in a pretty hard-wired and powerful way. It would be doubly unusual if the sustained existence of that bond did not lie at the root of psychic development.

“There’s no such thing as an infant,” the great psychoanalyst Donald Winnicott said, meaning that for untold millennia, any surviving infant had to have a feeding woman — biological mother or not — pretty close to hand. It seems undeniable that a predisposition to seek, to hold, to cling to the specifically female body is part of our given nature.

I cannot see how that reasonable assumption does not become centrally relevant to the question of same-sex adoption — and how it cannot but make clear that we are dealing with two radically different cases in same-sex female and same-sex male adoption. Women have always raised children collectively, and the sleeping arrangements are irrelevant at the crucial stage I’m talking about.

But to deprive a child of a figure it can call a mother, a female with whom it has had a pre-linguistic, bodily relationship, that strikes me as an utterly different type of act, a wrong against the child — and in that respect same-sex male adoption should be ruled beyond the bounds of what we permit culturally and legally.

When I advance this case to, well, y’know, the Tsiolkas BBQ crowd, rather than the John Howard BBQ crowd, the response is usually one of first incomprehension, then ridicule. The incomprehension is usually a gut response to the proposition that the structure of existence may mean that there’s a gap between what we want and what’s best for someone else, even when we’re all good people who recycle and carbon-offset. The ridicule comes when the forebrain realises this might serve as a challenge to that illusion and deploys the social constructionist idea that human beings are infinitely malleable, abstractable, transformable, etc.

This is ’80s nonsense, of course, but more interestingly the belief is contradicted by most of the shelf of parenting books people usually have above their Jim Jarmusch DVD collection. For increasingly parenting books are filled with the findings of neurology, biology, behavioural studies that suggest exactly how hard-wired children are, in terms of fundamental psychic categories.

Does that mean men should not be involved in infant parenting? Of course not. Does it mean that the argument about the limited malleability of infant development is certain? Of course not. Does it mean that some children might have terrible and destructive mothers they’d be better off without? Of course not. Nor does it suggest that every other issue has been settled on the side of consent. Should we really have sperm banks at all, regardless of who uses them? Or should we abolish them, and discontinue industrialised anonymous fatherhood altogether? And so on.

But what the argument above does suggests is this: serving the best interest of the child — always the aim of child-centred policy — means in this case erring on the side of prudence, and cultural and biological inheritance. Abhorrence or shock is never sufficient moral argument, but it is sometimes a clue to a categorical difference we should heed. To not have a father, because they were distant or absent from the start by choice is a sad thing for most kids. To not have a mother for the same reason seems somehow abominable, the measure of adult desires that cannot be squared with the universe, or the being of children.