06/02/2013 12:42 GMT | Updated 08/04/2013 06:12 BST

There's No Such Thing as 'Traditional Marriage'

It was a relief for me that the Commons voted so strongly in favour of gay marriage - not because I'd like to marry a woman - but for peace of mind that our politicians have not been time warped along with Richard III.

The so-called traditionalists, who claimed that allowing gay marriage would alter centuries of marital custom, don't know what they are talking about. The form and purpose of marriage is constantly being reinvented.

Like any societal or linguistic change, there are always resistors. But evolution is natural and results from changes in attitudes, desires and choices of the people. Nowhere is this more true than romantic relationships.

In researching my next book, F*ck the Fairytale, which examines modern models of relationships, I've found that increasing numbers of adults are abandoning 'traditional' models (the fairytale relationship, as I call it) and creating their own individualised dynamic for long-term relationships.

I put 'traditional' in inverted commas because what is historically seen as traditional marriage, is not what gay marriage opponents have in mind. What they see as 'traditional' is the heterosexual, monogamous, co-habiting, love-based, life-long union. In fact, the only time in history when this has been sustained and universally aspired to was one lonely decade - the 1950s. For most of history - from the beginning of civilisation until around the Victorian era - marriage was about practicality, inheritance, family ties and political relationships. Yes even for the working classes.

Not only that, for most of human history and in most cultures the most widely accepted model of marriage was polygamy, which is also the family structure most referred to in The Old Testament.

Opponents of gay marriage say that the opening up of marriage to homosexuals would cause problems for teachers and churches in explaining the meaning marriage to children. Well, this is no fresh problem. Sociologists have long struggled to find a ubiquitous principle. Go on, see if you can spot a pattern: In polyandrous societies a woman can marry more than one man. In polygamous societies a man has multiple wives. In some societies a woman can take another woman as a "female husband". In parts of China and Sudan children can be married to dead relatives! In Iran temporary marriages can be granted for as little as one hour. Tricky isn't it?

Commentators have dubbed the result of Tuesday's vote as one of the greatest historical changes to marriage. That's not so either. As historian Stephanie Coontz makes very clear in her book, Marriage, a History, the most consequential change to the way we conducted our marital lives and built families was when, in the early 19C, youth demanded a say in who they could marry.

"Heterosexuals revolutionised marriage and in doing so have paved the way for gay marriage. Two hundreds years ago people started to think love was important to marriage. One hundred years ago they began to think sexual compatibility was important. It was only in the 1930s that married couples had the right not to have children. Then in the 1970s, the 'head and master' laws, that gave men the final say in all household matters, was repealed. All these things that would have prevented gay marriage are the things which have been overcome in heterosexual marriages."

Just like the ruling on gay marriage, there were also vicious opponents to love marriages. People thought it would disrupt the foundation of society. But, just like 200 years ago, people power thankfully succeeded in pushing aside antiquated customs to make way for more socially relevant ones.

In researching my book, I have been astonished and enlightened to find such a rich tapestry of modern relationship models that resemble nothing like the mythical 'traditional relationship'. The goals, rules and interactions of romantic unions are now so wide and varied that they are becoming even more difficult to define.

We can no longer say pairing up is about starting families for I've met several women who've chosen to become mothers alone through sperm donors. I've met gay and straight men and women who've agreed to become platonic 'co-parents'. Marriage no longer necessarily means sharing daily lives for I've come across many married couples who live apart. Marriage is not always even about a sexual relationship if you an asexual couple. To them commitment is about finding an exclusive, trusted, but non-sexual partner whom they feel enough affection to share a life with. Their love does not need to be consummated.

Nor is marriage about calling time on sexual variety as there are plenty of in-love couples who have open relationships. For some marriage still isn't about love. A surprising number will admit their wedding vows were for financial or pragmatic reasons.

Resistance to gay marriage is a tell-tale sign of our obsession to box marriage and commitment up. It is the indoctrination of the fairytale happily-ever-after ending which causes such unrealistic demands on relationships. The more we allow couples (or groups, if that's your thing), gay or straight, to define their own dynamic, the more easy marriage will fit the zeitgeist.