We all tend to think of romantic love and sexual desire as going hand-in-hand, but they are the result of very different processes in the brain.

And the fact that they do come from different neural networks, and they really do involve very different subjective experiences, might suggest there were different evolutionary origins for romantic love and sexual desire.

Love and Marriage?

Basically we could reasonably assume that sexual desire was about mating and procreation, whereas anything associated with romantic love looks much more about the process of pair bonding for the purpose of rearing children. Socially that has become a process of ceremonial bonding – marriage. We all seem to assume that marriage follows on from falling in (romantic) love, but that is a cultural adaptation which Desmond Morris suggests is based in a human concept of fairness (one man, one woman for all).

If that’s true, it’s no wonder the men and women can experience feelings of sexual desire and love quite independently, but there are some questions that the scientists feel are unanswered.

If this was true, then people might feel sexual desire people of one or other gender and simultaneously be able to fall in love with people of a different gender.

Lisa M Diamond of the University of Utah has summarized the differences between romantic love and sexual desire; let’s have a look at what she’s got to say on the subject. 

Love and Sex

As we all know, sexual desire is about a need, perhaps a biological drive, to find sexual objects or engage in sexual activities, whereas romantic love is more about feelings of infatuation and attachment, perhaps combined with intimacy and a sense of empathy.

A lot of people researching love make a distinction between the first stages of love – which we’d call passionate infatuation or “limerence” – and the later stages of love, which are more about companionship and affection.

As you yourself might have experienced, it’s possible for both men and women to experience romantic love without sexual desire, or to experience sexual desire without love.

For example, in general, research seems to suggest that men and women can fall in love with people of either gender regardless of their sexual orientation.

One of the problems of investigating love is that there’s no clear test of what constitutes true true love, and it’s therefore hard to identify it.

Equally, it’s hard to be sure that you’re researching love consistently between different people.

But by putting together a group of behaviors, thoughts and feelings, psychologists have been able to identify the characteristics which seem to be common among people in love in different cultures.

According to the psychologists, therefore, passionate love is “a temporary state of heightened interest in and preoccupation with a specific individual, characterized by intense desire, proximity and physical contact, resistance to separation, and feelings of excitement and euphoria when receiving a partner’s attention.”

In later stages of love (which we could describe as more about companionship) the desire for proximity and the resistance to separation become less marked and are replaced by feelings of empathy, intimacy, security, care and comfort in the presence of a loved partner.

Neurobiology

A great deal of research on the neurobiological mechanisms of love and desire has been carried out.

We know that the primary driver for sexual interest is hormones from the testes or ovaries – and it appears that these hormones are not involved in the formation of loving feelings.

Love itself appears to be a product of the basic “reward” system in the mammalian brain, a system in which various chemicals such as oxytocin are involved. In essence, it appears that love is an intense feeling of what the psychologists call “reward” when you ‘re in the company of a loved individual.

But why should this be? It doesn’t really make logical sense that sex and love are the product of apparently separate neurological mechanisms. Why don’t they go together?

To answer this question, psychologists have drawn attention to the similarity of attachment between mother and infant on the one hand and attachment between two lovers on the other.

There are significant similarities:

• an intense affectional bond
• separation produces feelings of distress
• and proximity produces feelings of comfort and security.

Perhaps the natural evolution of the maternal – infant care-giving bond was “co-opted” for the purpose of ensuring reproductive partners stayed together to rear their offspring in the human species.

In fact when you look at the neurological mechanisms of animals caring for infants, and also animals which form pair bonds, you find that the biological mechanism is exactly the same for both behaviors. This tends to reinforce the idea that romantic love between adults is an evolution of the bond between mother and infant.

So if this was true, how could we explain some common observations such as the fact that women place a greater emphasis on relationships as a mechanism for sexual feelings than men do?

Love and Sex 

It could be that biological factors contribute to this gender difference: for example, chemicals like oxytocin and dopamine, which are responsible for bonding processes, are also involved in sexual behavior.

And these chemicals definitely affect men and women differently. They produce gender specific behavior.

Female rats, and therefore by implication female humans (who are also mammals), have much more numerous oxytocin brain circuits than males.

The reason for this is undoubtedly to facilitate caregiving behaviour between mother and infants, but interestingly enough, oxytocin also interacts with estrogen and regulates the rats’ sexual receptivity.

Unsurprisingly, since this is most likely an evolutionary mechanism, women show greater oxytocin release during sexual activity than men, and there is even some evidence to suggest oxytocin is related to orgasm intensity.

An inevitable conclusion is that women find sex more desirable, acceptable or enjoyable within the context of an intimate relationship than men could be a product of the higher levels of oxytocin in the female brain.

Another observation which is perhaps less well-known that many women who have had sex with another woman report that they had no desire to engage sexually in this way until they fell in love with another woman.

This is not something that men seem to report very much, if at all.

Could it be, therefore, that the higher levels of oxytocin and similar chemicals in a woman’s brain allow her to connect love with desire, even when these desires override her usual sexual orientation?

Probably. And underpinning this research is an assumption that sexual arousal is a basic biological process, while romantic love is more mind-centred. What we can say for sure is that current research demonstrates culture, socialization, and neurochemically mediated processes all affect the behaviors and feelings associated with both romantic love and sexual desire.