TWO years ago, the world was shaken by the news that we had reached what experts were calling “peak beard”. Well alright, maybe not the entire world. But certainly the part which cared deeply about tonsorial trends and which kept in its medicine cabinet bottles of Colonel Ichabod Conk's Natural Beard Oil (three scents available: Santa Fe Cedar, Rio Grande Lavender and something called High Desert Breeze).

The “peak beard” theory was proposed by researchers at Australia's University of New South Wales and in its simplest form it ran like this: when you reach a point where the majority of men have beards, the ones who don't stand out and start to look more attractive as a result. That point, the researchers thought, had been reached. Hence peak beard.

The study involved 1,453 heterosexual or bisexual women looking at images of 36 men, some bearded, some not. The upshot was that the more beards the women saw, the less attractive they found the men wearing them, using a ranking system of one to four. It's all to do with something called “negative frequency-dependent sexual selection”, apparently. But the important words there are the first one and the last two. Given that ultimately most men grow beards because they think it makes them more likely to be on the receiving end of that sexual selection, you can see why a certain amount of panic set in.

But, like the Scottish summer or contrition among celebrities, panic is a fleeting thing. Two years on, the ubiquitous beard has either not peaked at all, or it's spending so much time at the top of its trajectory that it's threatening to redefine the laws of physics.

In short (or long, or bushy) there are still an awful lot of beards around: on hipsters (naturally) but also on dads, middle managers, footballers, doctors, bus drivers, lawyers, IT guys and even a politician or two. And those men who held back from shaving two years ago may also have the last laugh. Another Australian study, this one led by a Dr Barnaby Dixson of Queensland University, found that while there certainly is a danger of peak beard, it's still in the never-never. Instead, the Queensland psychologists found that facial hair is actually still attractive to women.

“Beards may enhance perceived masculinity and dominance by amplifying aspects of underlying craniofacial masculinity, particularly the size of the lower face and jaw,” they wrote. “Attractiveness ratings were highest for bearded faces with smaller jaws followed by bearded and clean-shaven faces with larger jaws. They were lowest for clean-shaven faces with small jaws.”

Got that?

Interestingly, however, it isn't all about the jaw. How bushy the beard is also makes a difference. It turns out that women are more likely to undertake a “short-term relationship” (and we all know what that means) with a man sporting what the researchers call “an intermediate level of beardedness”. Or, in plain English, a Jeremy Corbyn. Men with full beards on the other hand, are seen as better long-term partners who are more likely to make tip-top fathers and family men. This sort is known in the parlance as “a keeper”.

Clearly, then, beards are still A Thing. So much so that there's even a sort of dating app for beards, called Bristlr. “There are many people with beards who like to have them stroked,” explains the website. “And there are many people who don’t have beards, but would like to stroke them. Bristlr is the link between the two”.

All this is very good news for Barcelona-based journalist, blogger and beard enthusiast Carles Sune who this month publishes This Bearded Life, a love letter to the beard which, like any good billet-doux, comes complete with hand-drawn illustrations.

The book features grooming tips, gives a cultural history of the beard, dips into the rebirth of the barber shop (though not the barber shop quintet, thankfully), presents a sort of Beard Hall of Fame (yes, ZZ Top feature) and tries to answer a question that has dogged men since the beginning of time: does size matter? In that regard, Sune has a simple answer. “A beard,” he writes, “should not be measured in centimetres, but in months.”

The way Sune tells it, though, he's an accidental convert to beardedness. It was only when he was promoted at work and decided he needed a more authoritative look that he decided to grow one. “But I soon realised that sporting facial hair not only gave me more presence; I also really liked how it looked. That was when I knew that my beard was to become an integral part of who I am. Times has passed and it has remained ever thus. We've had moments when we've drifted a little, my beard and I, but our relationship can withstand anything.” Except a razor, presumably.

In a section on the connection between beards and masculinity, Sune too cites the work of Barnaby Dixson. But he also quotes the Spanish photographer Javier Hirschfeld, writing in the catalogue for an exhibition about the representation of beards in art: “The beard represents maleness because it is unique to men: it distinguishes one gender from the other. This translates it into an object of desire, the iconic epitome of masculinity and virility.”

But if that's the case, why haven't beards always been fashionable among men who want to exude masculinity and virility? Partly it's because the fashion wheel has turned and the beard, last seen on the hippies of the late 1960s and early 1970s, has replaced the clean-shaven look which dominated in the 1980s and for most of the 1990s.

But it's also because in many cultures and in many periods of history, the opposite was held to be true: it was the clean-shaven man who displayed many of the supposed masculine virtues, notably aggression and prowess at arms.

It's an idea that goes back at least as far as the Romans. Obviously shaving was difficult until decent metal blades were available, but around 600 BC, King of Rome Lucius Tarquinius Priscus introduced the razor. Shaving caught on, if slowly, and by 200 BC the famous Roman general Scipio Africanus was said to be doing it every day. It's safe to assume his officers and men would have copied him.

Six hundred years later, Roman soldier and historian Ammianus Marcellinus railed against beards on the grounds of cleanliness and took aim at the Greek idea that they implied wisdom and sagacity. “Take my advice and shave it off at once,” he wrote, “for that beard is a creator of lice and not of brains.” Mind you, by then the Greeks had long since come to the same conclusion. Alexander the Great made all his men shave before battle. Among other things, he said it gave the enemy less to hold on to in a fight. (Many centuries later, bearded 1970s wrestling star Giant Haystacks would find this out to his cost.)

So there's a long tradition of soldiers keeping their hair short and their faces clean-shaven. When given arms and gathered together in their thousands – it's called an army – it's easy to see how that same look could come to be associated with aggression.

Fast forward a couple of millennia and you won't find a better symbol of leering aggression than the skinhead who, by definition, is close-cropped and clean-shaven. Staying with subcultures, others who made great play of their masculinity and virility – the Teddy Boys, say, or the Mods – were also clean-shaven. Meanwhile the only two subcultures in the street style annals who actually sport beards are the hippies, who stand for peace and love, and the modern-day hipsters, who stand in queues to buy iPhones or order flat whites.

So much for the skinheads and the Teddy Boys. Far less fashionable, but proving just as resistant to the lure of the beard, is another dangerous subculture: politicians.

As far as most American senators and congressional representatives are concerned, beards are for anti-globalisation protestors, Muslims and members of biker gangs and as they're keen to keep all three away from the levers of power, the beard-as-Capitol-Hill-fashion-accessory hasn't taken off Stateside. If you don't count those married US presidents who were rumoured to be gay, the last resident of the White House to live with a beard was Benjamin Harrison, who served until 1893 and had seen action in the Civil War.

In the UK, it's a similar story where bearded politicians are concerned. Stephen Crabb's is-it-or-isn't-it? designer stubble was one of the highlights of the Tory leadership run-off, but it's often only when they're out of power (Al Gore) or out of power, branded a pariah and shouted at in the street by strangers (Michael Gove) that they dispense with their morning shave and sprout some facial hair. Mind you, if anything would make you believe we'd reached peak beard it was Gove's effort.

But perhaps even this political heel-dragging will change. An overlooked aspect of the recent Labour Party leadership election was the way it turned into a beard versus non-beard face-off.

In the (some would say distressingly) red corner was Jeremy Corbyn, he of “intermediate level of beardedness” fame. In the not-quite-so-red corner was the smooth-cheeked Owen Smith. And note this: it was the beard that carried the day (as well as bits of the day's lunch which, as all beard owners know, is an occupational hazard).

All this suggests that beards will be with us for a while and that the time of peaking is not yet upon us. But if you want incontrovertible proof, look no further than the web. As we all know, mining Google Trends for internet search data is now the mutually agreed way to take the temperature of any and every human trend and predilection. And so it is that we find searches on terms such as “beard styles” and “beard styling” steadily increasing. You can see it mapped out in a steadily rising graph that even a beardless child could understand.

So even as you read this, someone is probably typing “beard oil” into Google (searches for that term are up 250 per cent, by the way) and trying decide between the Santa Fe Cedar and the Rio Grande Lavender. Or maybe they're wondering if High Desert Breeze smells as much like a toilet freshener as the name suggests. Either way, Colonel Ichabod Conk will be delighted - and the beard will be here to stay.

This Bearded Life by Carles Sune and illustrator Alfonso Casas is out now (Aurum Press, £12.99)