Katie Byrne: Why do young women fall for auld fellas

"That's a rather full-on kiss to be giving your father," I thought. My initial shock was superseded by realisation, though, when the man was identified as her partner, and not her dad. Tommy Joyce is 34 years her senior. Some people get it all.

Not only is Joyce sharing in the spoils of a €7.5m prize fund, but he's already won the relationship lottery by landing himself the jackpot: a young one.

When it comes to older men dating younger women, we often assume that a thick wad of cash has wedged the wide age gap. The roles, in this case, have been dramatically reversed.

Ryan was never a kept woman or a sugar daddy's girl. She is in fact a co-owner of the couple's busy import industry. It's a story that smashes all the stereotypes.

And when it comes to age-gap relationships, stereotypes abound. "Ambitious, balding man with attractive bank balance and inferiority complex seeks mercenary young woman with a taste for fancy shoes and a father complex." Admit it, you've made the assumption more than once. We all have.

But what about the Michelle Ryans and Tommy Joyces of the world? Could it be that -- whisper it -- true love brought them together? Or are they just another poster couple for the older man/younger woman relationship dynamic?

Marriage records all over the world show that women seek out older husbands and men younger wives, while the success of wider age-gap couplings has been empirically proven.

Fertility

According to evolutionary scientists, it's all in the genes. The phenomenon of older men chasing younger women is a classic example of natural selection. In the most simple terms: an older man and younger woman promotes survival of the species.

Women's fertility has a time limit; men's does not. Men seek out women who are visibly fertile and youth is fertility's hallmark. Women, meanwhile, seek resources and status, which increase as a man gets older.

Darwin's theory was backed up by a study by Gothenburg University and Oxford University that studied 400 lonely hearts ads to see how men and women choose partners.

Men in all categories preferred younger partners. Of a total of 97 men who mentioned age in their ads, only three were looking for an older partner; among men aged 40 to 59, only one out of 67.

Younger women preferred older men. 14 of 16 women aged 20-39 were looking for an older partner. (Among women over 60, however, the majority were looking for a younger man.)

It was also found that women, more than men, look for solid resources and social status, which is why men often offer enticements such as 'large house' and 'economically independent' when they pen their lonely heart missives.

Another study has revealed that men have more children if they marry women younger than themselves. Originally it was thought that 4-6 years was the optimum age gap, but later studies have widened it to 15 years.

Hollywood offers many age-gap examples. It's often said that the younger women who date older men in Hollywood have offered up their youth and beauty in return for profile raising and career opportunities; but there is a similar number of successful female celebrities in Hollywood who are linked with similarly successful older men.

There was 20 years between Angelina Jolie and Billy Bob Thornton; there are 25 years between Catherine Zeta Jones and Michael Douglas and 22 years between Harrison Ford and Calista Flockhart.

The film industry has also bolstered the cultural stereotype by consistently pairing older actors with younger leading ladies. Consider the on-screen pairing of Harrison Ford and Anne Heche in Six Days Seven Nights and Catherine Zeta Jones and Sean Connery in Entrapment.

Hollywood didn't create the stereotype, it reflected the social trend.

Likewise, when older women are cast against younger men the story often carries a sexually explicit or perverted undertone. These days it's comedic: enter the latest Hollywood import -- the cougar. Why do women earn such a dangerous tag when they are just doing what men have been doing since time immemorial?

Consider Iris Robinson. Leaving aside her obvious hypocrisy, infidelity and political misdoings, ask yourself would you feel differently were it a male politician and a 19-year-old girl? Somehow, it would be a smidgen more acceptable.

Why? Because it's nature's way. A man with a younger woman commands a quiet respect, a woman with a younger man stirs our disgust. Somehow we can't separate an older woman's roles as maternal facilitator and lover.

Maturity is a factor, too. Nineteen-year-old girls tend to more emotionally developed than 19-year-old boys.

In fact, 29-year-old women tend to be more emotionally developed than 29-year-old men.

Anecdotally speaking, women mature faster, which makes many seek out the company of older men.

Age-gap relationships bridge the maturity divide and allow a man to embrace his delayed childhood without the tut-tuts of a partner who is fast reminding him of his mother.

Even so, there are always challenges, particularly when the age gap goes beyond the eight-year mark.

Older men often come with baggage: namely a gaggle of children and an irate ex-wife.

Older men's social lives are less energetic, which often leads to jealousy when their young partner is reluctant to hang up her dancing shoes, and resentment -- particularly in later years -- if she is encouraged to do so. (I can't see Michelle and Tommy pitching a tent at the Oxegen festival, can you?)

Where there are very wide age gaps, the younger partner needs to accept that they could eventually become a carer as their partner declines into their dotage, or worse, that their partner might not be around for all of their children's graduations.

When both parties pass their prime, Darwin's theory begins to unravel.

Mind the gap.