Relationships are, by their nature, competitive and perilous enterprises. They are our most primordial games to play, with high stakes - survival, protection, creating a new generation - and possibly even higher ones now.

We have chased a formula for attraction since time immortal, be it through superstitious rituals like peeling an apple in one continuous loop to ascertain good luck in love, or distilling the complex and baffling interactions that lead to love, down to glances, "meet cutes" and - always - fate in rom-coms like When Harry Met Sally. We’ve founded entire festivals around it across every culture, and with 6,000 people flocking to the matchmaking festival in Lisdoonvarna, Co Clare, each year business is booming.

The intervention of technology into this base quest for a mate has only fuelled our frenzied need to decode relationships. As more of our interactions become augmented, programmed and categorised, the more we search for the "cheat codes" to win romantic games.

The Matchmaker pub in Lisdoonvarna, Co Clare. 

Turning away from the scripted rules of religion, the lovelorn have moved in exodus to the temple of science, where we leave offerings in the form of DNA samples, brain wave readings and personality tests in the hope of better understanding how and why humans connect with one another.

"Once science begins to look at something, you begin to get some truths, because science is all about the truth", says Luke O’Neill, a professor of Biochemistry in the School of Biochemistry and Immunology at Trinity College and a Fellow of the Royal Society, the world's oldest independent scientific academy. His book Humanology: A scientist’s guide to our amazing existence, in addition to a range of essential human questions, probes into what science tells us about human connection and what impulses govern each obscure impulse.

Whether those truths are reassuring or not is open for debate.

Science has put words and studies to preferences we’ve seen for years, such as the ideal body shape of a man and a woman. "A great example is a man will look at a woman and within a microsecond the hip-waist ratio goes into his brain, and seven to 10 is the optimum", O’Neill explains. "A woman looks at a man and it’s the shoulder-waist ratio, and that’s 10 to nine. And every culture has that and it’s instant."

"So in other words we are programmed - we are machines, sadly - and we respond quickly to these cues. And biology built this because we’ve got to have offspring."

O’Neill explains that these ratios are "surrogates for having strong genetics", markers that point to your ability to provide healthier offspring than the couple in the next hut. Wider hips on a woman means "she’s got a bit of fat on her, which is good for sustaining the embryo". In men, broad shoulders suggest strength and an ability to protect.

More intriguing are non-physical preferences. If all of our romantic interludes are in the service of creating offspring, why are women attracted to risk takers and vagabonds? "The man who, say, does a bungee jump or perhaps is a musician, that’s a big one actually, or is a sportsperson, they’re seen as attractive traits because they speak about good genes in the man", O’Neill explains.

No longer can we pretend we "just like the guy’s music", as studies show that women act differently when ovulating. When ovulating, a woman is attracted to the risk-taking "bad boy" type and when the egg is fertilised, she’s attracted to the kinder male who is less dangerous, steadfast and likely to help raise their offspring.

So, for the love of god, spare yourself the heartache and remember that before you ask another struggling musician for his number. There’s nothing risky about not being able to stock his fridge with food or have a normal sleeping routine.

Though it’s not so bad falling victim to the charms of an aspiring Jeff Buckley if we’re to compare the offerings with other cultures. "There’s a tribe in Papa New Guinea, they drink petrol", O’Neill says, "and the women find that attractive - ‘he can handle that petrol!’"

There are real life consequences to this quirk of biology, however. O’Neill points to medical inventions such as the contraceptive pill that alters a woman’s hormone levels and creates a "pseudo-pregnancy", disrupting this primitive call from nature. According to him, while on the pill a woman will prefer kinder men, and when they come off it - perhaps to get pregnant or for any number of reasons - she’ll be more attracted to risk takers again.

This works in converse, too: "This may give rise to problems in the marriage, because she marries the rough guy and realises ‘I don’t want him anymore, I want the kind guy.’"

This isn’t even the most unsettling fact that science has thrown up about relationships. Multiple studies have shown that people are attracted to someone that resembles a family member. "They’ve analysed couples and there’s a likeness, a physical likeness between the man and the woman", O’Neill says. "A woman is attracted to a man that looks like her father or brother, and the man, like the mother or sister. We think this is because they’ll stick around, interestingly enough, they’re part of your tribe and we’re quite tribal as a species."

"But you don’t want to go for someone too like you, because that’s inbreeding, and that’s dangerous."

It must be said that these studies are often with small sample sizes, in countries with their own unique preferences and concerning predominantly heterosexual couples, a bias that is increasingly becoming incongruous with our global culture. While technology has upended many innate biological impulses when it comes to relationships, there can be no shift more impactful than the reevaluation of gender. After all, if relationships are games, what happens when the players are recast?

O’Neill asserts that if the fundamental purpose of relationships is to create the next generation, then that will prevail over shifting concepts of gender. "Lesbian couples, they want kids, so it’s not that if you’re lesbian or whatever you’re not going to want to be a parent", he says.

Shifting ideas of gender and sexuality are changing relationships

"The gender fluidity is interesting, because you have to pick a gender eventually, probably. If you switch from male to female you may still want kids, anyway. So it seems as if the desire to procreate no matter what your orientation or gender might be."

It’s no coincidence that with so many factors that influence how we connect with one another undergoing such profound change that we’re turning towards the hard facts of science to define relationships. Studies on ghosting, dating apps and sex, that in another era may never have garnered mass attention, are devoured shortly after publication. There are reactionary articles, think pieces and probing deep dives into their findings. Aside from being just an example of our penchant for consuming information, we’re looking for answers.

O’Neill puts it down to that well known feeling of rejection and bafflement that colours any teenage romance, and the enduring concerns it creates. "You’re hoping to put some order on this. And if you’re scientifically inclined, and most people are, they will look for data and ways to predict this, to give them comfort."

"You will use any strategy you can think of. It might be that you dress in a certain way, or you go to the ‘right’ nightclub or you use data, and there’s no harm in that."

O’Neill says that we’re only experiencing a minute amount of the advances technology can give us and our quest for love, as devices and services become ever more sophisticated. "Maybe before you meet the person you’ll find them online and it’ll be more predictive than ever. It might end up with the smartphone scanning the person, isn’t that terrifying? People are proposing this! At the moment that’s not the case whatsoever, you cannot predict it."

Ever the workability-orientated scientist, O’Neill predicts that where this technology will cause real harm is if it becomes widespread and turns out to not be predictive at all, leading unsuspecting machine-humans into relationships they have no reason for being in in the first place.

"Blade Runner 2049" explored the how relationships may work in the future

And regardless, present technology can’t deliver what basic biology can. "It’s still not good enough, though", says O’Neill. "When you meet someone in person, there’s an awful lot of stuff happening there physically that you can’t recreate with an avatar or a robotics system at the moment."

So what’s the biological key to relationships that holograms, software systems and apps can’t hope to deliver on? Smells.

"Marvelously, it turns out we’re picking up on smells off each other!" says O’Neill, who, as an immunologist, has a vested interest in this area of study. "You’re sniffing the other person for their pheromones, and you pick someone with an immune system that’s different to yours. The reason for that is if you have a  baby with a mix of our immune systems, it’s more likely to survive infection."

"A good example is when a woman is ovulating, which means she’s receptive now to have her eggs fertilised - this is really basic biology, the mission here is to get the eggs fertilised! - she will exude a pheromone which will attract the man in to fertilise the egg." This was scientifically observed in experiments that involved asking men to smell t-shirts worn by women and rating them based on attractiveness. "And they rated the ovulating woman as the most attractive", O’Neill says. A similar experiment can be done to prove why we’re not attracted to our own family members.

Another shifting facet of relationships is monogamy and more open relationships becoming more normalised. O’Neill sees parallels between this need for greater freedom and the tribal mentality that is encrypted into our DNA. "Humans are called ‘mildly polygamous’", he explains. "That’s our category, so we do need a mate. We try to mate for life, but then we stray and there are reasonably high instances of straying."

According to the OECD’s latest figures on divorce rates, Ireland is one of only six countries in its remit of 36 globally to see divorce rates increase since 1995, while various surveys have put divorce rates as high as 50% in some countries. If the confines of relationships are to continue shifting with technology and culture, it is likely further increases in divorce - or decreases in marriage in general - will continue.

He suggests that one antidote to this is to "own up" to our biological predilections for varied partners and embracing polyamory. "Now, people don’t like that, and that can be cultural." Religions were possibly privy to this trait in humans and attempted to batten it out with the sacrament of marriage, a rule book on keeping your inner tribal ape in check. Now, however, the focus is increasingly on freedom, says O’Neill. "If you were in a strict religion that was terrible, really, for relationships."

The Belgian psychotherapist Esther Perel writes that the "quality of our relationships affect the quality of our lives", and in a world becoming ever more interconnected, this is perhaps one of the most prescient perspective on relationships. How do we continue our quest for love when the rules are being rewritten by forces far beyond our reach? O’Neill says it comes down to empathy, as love always must. "The most important thing is that people respect each other. Caring is the key word here."