Any mother collecting sweaty T-shirts left in a pile in the corner of their teenage son’s bedroom can attest to how unpleasant this task is. What might surprise them is that the experience may not be nearly so unpleasant for another woman.
The abundant pheromones in male sweat provide a potent clue to the owner’s major histocompatibility genes. While these genes play an important role in immune surveillance they also send powerful signals to any potential female mate.
Studies suggest that the more different a man’s histocompatibility genes are from her own, the more attractive a woman finds him – thus the reason for teenage son’s pong.
Interestingly, women also have a heightened sense of smell at mid-cycle when oestrogen and fertility levels are at their highest.
This is how evolution ensures that genetic diversity is maintained and offspring are likely to be healthier and have a more robust immune system.
Enter the hormone-based contraceptive pill
For at least the last five years, there’s been speculation that the alteration of hormones in women taking the contraceptive pill affects their ability to choose the most suitable long-term mate.
A number of scientific papers published in 2008 suggested women on the pill were not only less able to pick up gene similarity than their naturally cycling sisters, but were also less likely to show a preference for more “masculine” males.
The theory goes that, if the pill does in fact alter a woman’s perception of male attractiveness, it might not only skew her choice of partner but have a long-term impact on her reproductive success.
In the worst case scenario, a woman stopping the pill might one day look at her partner and suddenly ask herself, “What was I thinking?”
But it’s not all doom, gloom and relationship breakdown.
When not under the influence of spiking oestrogen levels, women seem to find the alpha-male stereotype far less attractive.
Instead, they prefer the caring/sharing type: the type of man who makes a better long-term partner and father.
Dr Craig Roberts is a psychologist from the University of Sterling in the United Kingdom, who first co-authored a paper on this topic in 2008.
He and other researchers have explored these issues further in a paper published last week by the British Royal Society.
Their ongoing research indicates that women who met their partner when they were on the pill report less sexual satisfaction over time but also appear to be more satisfied with other aspects of their relationship.
To quote Dr Roberts, “Overall, women who met their partner on the pill had longer relationships – by two years on average – and were less likely to separate. So there is both good news and bad news for women who meet while on the pill. One effect seems to compensate for the other.”
The suggestion is that cautious women may like to consider a few months off hormonal contraception to reduce the risk of “pill-goggles” before making a strong commitment!
More than meets the nose
Most of those working in sexual medicine would contend the question of sexual attraction between couples is far too complex to be explained pheromones alone – and, of course, Dr Robert’s research makes no reference at all to same-sex couples.
The reality is that both men and women mask their natural “perfume” with decidedly unnatural ones and by bathing regularly. All this makes it much harder for any potential partner to read the underlying hormonal signals.
Successful bonding is also driven by social considerations. For most couples in long-term relationships, the mad frisson of passion experienced in the first few months mellows into something more substantial over time: commitment, respect and, with any luck, love.
Sex can still be great in a long-term relationship but it’s probably true that most couples have to work a little harder at it over time.
The alternative is a series of short-term relationships, churned as soon as the adrenaline dissipates.
Dr Robert’s research provides a fascinating insight into the primitive drivers that subconsciously shape our lives and our choices.
But while histocompatibility genes may indeed provide the spark in a new relationship, keeping that fire blazing is ultimately up to the couple.