Right now, roughly a third of the adult population in the Western world could legitimately tick 'single' under relationship status.

In some ways, it's never been easier to meet people, so why are so many of us alone? Evolutionary psychologist Menelaos Apostolou wanted to come up with a theory. So where better to turn than that forum of sages – Reddit.

The question of how or even whether our ancestors evolved to partner up is a contentious one that served as ground for a lot of debate in recent years.

But while we all have our opinions on why finding 'the one' is so hard, there isn't a scientific consensus on what drives relationship trends. Speculation aside, we're lacking academic underpinnings on the nature of hooking up.

"Understanding singlehood requires at least two explanatory levels, namely a theoretical and an empirical one," Apostolou says in his report.

Empirical observations can only take us so far, providing simple explanations on a case-by-case basis. To really get to the bottom of it, we need a sound theory that tells us why.

Apostolou used the discussion website Reddit to collect responses to a question that didn't beat around the bush – "Guys, why are you single?"

While the question focussed specifically on one half of the population, it didn't limit itself to heterosexual relationships, seeking deep (and, well, not so deep) reflections on why men of all sexual persuasions weren't somebody's snuggle-bunny.

The 20,207 replies in the thread were whittled down to 13,429 actual responses, presumably after gifs, incoherent mumblings about lobsters, and armchair psychologist conjectures were whittled out.

After further analysis, there were 6,794 quality answers that could be coded into 43 categories.

Are you ready for the top five?

Coming in at number five, with 421 responses, was a claim to possess poor flirting skills. "My IQ drops to about 40 whenever I talk to women," said one pensive Reddit reader.

At four was a simple lack of interest, with statements like, "I like my freedom and privacy."

Number three blamed a lack of effort. "I've always believed relationships come and go on their own," said one rather zen responder.

Low confidence came in at number two. "Confidence is the key, and I′m locked out," one guy quipped.

And the number one reason why Reddit guys think they're not in a relationship, with 662 responses is … unattractive looks.

"Cause I am ugly as fuck and have been cursed with awful genetics." Cue awkward cough.

Not to validate any of the responses, the list makes it clear that there are a bunch of common concerns that point to a potential framework explaining why a number of men in today's world are single.

Rewinding the clock to simpler times, there were diverse ways for relationships to form. Some were arranged. Others the product of limited opportunity, or other social pressures. In such cases there was little need for most men to display their charms.

Apostolou wonders if those same Reddit readers who sought relationships might have had more success in pre-Industrial times. Answer: probably.

"Single modern men often lack flirting skills because in an ancestral pre-industrial context, the selection pressures on mechanisms which regulated mating effort and choosiness were weak," says Apostolou.

"Such skills are needed today, because in post-industrial societies mate choice is not regulated or forced, but people have to instead find mates on their own."

Reading between the lines, it could be fair to say Apostolou's theoretical framework claims levels of male isolation in today's world are simply down to the fact that culturally speaking, men have never needed to really make an effort until now.

Well, not all men.

It goes without saying that the study could benefit from a wider sampling, perhaps a comparative investigation from a non-male perspective, using different sources.

But the study does offer some food for thought on the matter of interpersonal relationships in the age of Tinder.

There's plenty of room for debate in this theoretical model, which no doubt Reddit will deliver.

This research was published in Evolutionary Psychological Science.