As we discuss the possible introduction of gay marriage, we often hear expressions of the “enlightened” view that marriage is a “man-made” institution. I’m 100% in favour of gay marriage, but I can’t agree with that view. Human culture is just an extension of human nature, and it is a mistake to see aspects of culture as working “against nature”. Culture instead adds detail to innate biological urges and abilities. For example, human languages differ from each other because they developed along different lines. In other words, they were so developed by the people who spoke them, and in that sense they were “man-made”. But the fact that every human speaks some language or other indicates that language use is innate. It is not “artificially imposed” on human nature by human culture as an optional extra. Marriage isn’t artificially imposed on human nature by human culture either. As with language, all human cultures seem to have some form or other of marriage, as indeed do some other animals such as monogamous birds that observe public courtship rituals. This indicates that marriage serves a biological “purpose”, like erotic love itself.
The biological purpose of erotic love is committed parenthood in monogamous species. These are species in which offspring are a big investment for both parents, so big an investment that both parents have to be firmly committed to their role as parents and bonded to each other as a pair. Public “ceremonies” seem to add “cement” to such pair bonds. The extra “cement” is advantageous in species whose offspring represent an unusually large investment, such as humans. There’s a selective pressure for a more durable bond, because monogamy is always threatened by infidelity, which also serves a biological purpose (although a slightly different one for each sex). No species is perfectly monogamous in that none of its members cheat, although in many species some pairs are perfectly monogamous in that neither member ever cheats. At the level of entire species, monogamy is always less than perfect, even among those whose fidelity is legendary such as swans. Thus the presence of cheating among some members of a species does not diminish the claim of the species as a whole to be a monogamous one.
If love and the institution of marriage are “natural” for humans because we are a monogamous species, changing them or common perceptions of them might be more difficult than we think. It doesn’t matter what other people think about love, because that only exists between two people. Homosexual love obviously exists and always did exist regardless of homophobic attitudes of the surrounding culture. But marriage is another matter. For it to exist in the proper sense of the word, it has to be widely recognized as marriage by the surrounding culture, and I’m not entirely convinced that’s possible with homosexual marriage just yet. I wish it were possible, but I’m being realistic.
Since homosexual sex cannot result in parenthood, it is not surprising that many people see homosexual love and marriage as “not quite the real thing”, as biologically secondary to heterosexual love and marriage. Of course we must not draw any “oughts” from that unpalatable fact, but I think we should at least acknowledge it as a fact.
As I write, proponents and opponents of gay marriage are being urged to sign online petitions for or against. The “anti” vote currently stands at almost ten times the “pro” vote. If those numbers reliably reflect popular opinion, that would be disappointing, but hardly surprising, as it simply reflects human biology. It would be disappointing, because it probably means that for now, even if gay marriage were made possible in the full legal sense, it would not be widely recognized as marriage.
This isn’t always a sign of homophobia. Humans are intensely interested in erotic love, for the obvious biological reason that human children are a sort of “life sentence”. A single human childhood is easily the longest and most resource-consuming project in the living world, so the choice of who to marry and/or have children with is a biologically momentous decision – it’s literally a matter of life and death, not only for the children but also for the occasional suicidal abandoned spouse or murderous cuckolded non-parent. Erotic love is the central preoccupation of human art. We are all fascinated by the many variations on the theme of love, and we all speculate about how well or badly the old, the young, the rich, the famous, above all the different will fare in the dangerous game of marriage.
If we’re honest about it, we all wonder how well or badly things will turn out where there are big age differences, religious differences, racial differences, or differences in social class. And we see the importance of sameness as well. Most of us see various strengths and weaknesses in the various possible similarities and differences. For example, most of us are ready to accept a big age difference if the man is older than the woman, but raise an eyebrow if the man is younger than the woman – especially if the man is poorer than the woman.
If we’re honest about it, most of us realise that marriage between a man and a woman can be hard going, but the long trek unto death is made slightly easier by a sort of complementarity between them. If the man is a boor and the woman is a shy accepting little mouse, that is horrible – but at least their minds are made for each other like sex organs. If the man is a hen-pecked weed and the woman is a harridan, that is not quite so bad, but again: at least they are made for each other.
This brings us to the crux of the problem: Why are so many of us apparently not yet ready to recognize marriage between two people of the same sex? – I think we see (or think we see) a lack of complementarity between the people involved. I for one do not see any such complementarity, bad and all as heterosexual marriages often are, and I would be amazed if the mean length of non-married homosexual partnerships was anything like as long as the mean length of non-married heterosexual partnerships. That is one of the reasons I support homosexual marriage: it might add “cement” to homosexual partnerships in the same way as it does to heterosexual partnerships.
No doubt what I’ve written here will strike many as homophobic. And I am a heterosexual, which does not portend well. But I have had unusually intimate relationships with homosexual men and women for much of my adult life, through one accident of fate or another. Much of what I know about evolutionary biology I learned from the greatest – and incidentally homosexual – philosopher of biology there has ever been. I think all of them would agree with what I have just written, and all have expressed views very similar to my own.