“A woman must continually watch herself,” is a John Berger quote you might remember if you studied art at school, or if you like watching bad 70s fashion in action on YouTube. The theory (from his 1972 documentary series, Ways of Seeing) goes, “from earliest childhood [each woman] has been taught and persuaded to survey herself continually … how she appears to men is of crucial importance for what is normally thought of as the success of her life … This determines not only most relations between men and women but also the relation of women to themselves.”

It’s a useful quote to pull out if you’re writing an essay about the ubiquity of naked female paintings throughout history. It also works well as an answer to the question asked by a new academic study this week, “Why are there so many sexy selfies of women everywhere these days?”

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The subject of female vanity has been a preoccupation in the creation of images, and in their analysis, for centuries. Before think pieces about the prevalence of women posting #sexy stuff on Instagram, there were male artists at the salon exhibiting paintings of women looking into mirrors to see their own tits. There was Celebrity Big Brother’s Hardeep Singh Kohli disapprovingly asking Chloe Ayling if she felt objectified while glamour modelling this month. Early Woman might have been tutted at for scratching a likeness of her pubes into a rock – we don’t know for sure; no one’s proved it yet.

Berger’s “Men look at women. Women watch themselves being looked at” is a fair summary of societies that create and distribute so many images of naked women (ours). An updated but similar conclusion being put forward now, from the realm of scientific study rather than art theory, comes from Dr Khandis Blake of the University of New South Wales.

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For Blake, the reason women post so many sexual selfies on Instagram goes like this: “These behaviours are completely rational, even adaptive … it’s all about how women are competing and why they’re competing … When a young woman adjusts her bikini provocatively with her phone at the ready … think of her as a strategic player in a complex social and evolutionary game. She’s out to maximise her lot in life, just like everyone.”

It’s as it ever was, then. Female flesh is offered up to be looked at. Offering it up to be looked at can bring rewards for the women who take part. That’s the glamour industry, that’s pornography, that’s pole dancing. That’s women parlaying their followers on Instagram into brand sponsorships and appearances on Eric Andre Interviews the Hot Babes of Instagram. What’s new is how Blake and her colleagues frame this. Apparently, it’s not about the power of the straight male gaze, or patriarchal pressure. It’s about economics.

In analysing 68,562 selfies on Instagram and Facebook tagged with words like ‘“sexy” and “hot” from 113 countries across the world, Blake’s study concluded that women are more likely to post sexy selfies in places where “economic inequality is rising, and not in places where men hold more societal power”.

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Being a woman who looks a bit like Garth from Wayne’s World, I don’t make money or climb social hierarchies with sexy selfies. But I would very much like to scrape my coins together to pay for a ticket to the place Blake knows where there’s no gender imbalance. It sounds great. Where is it? Can someone draw me a map?

To back up the (very established by now) point that sexual images of attractive women have value – monetary and social – without factoring in why they have that value ignores the important bit. Yes, women who use this strategy to gain influence and money shouldn’t be shamed for narcissism, considered stupid, or pitied – we’re all operating in a system that offers certain options to us, and working to gain reward.

But what created the system? That young woman pulling her phone out to post a picture of herself pouting in a bikini is working within a structure – one that’s been passed to her through time. She didn’t create it, and doesn’t have full control over it, not really. And that isn’t a #hot or #sexy thought, but, then, being faced with the reality and limitations of longstanding patriarchal structures never is, is it?

• Phoebe-Jane Boyd is a content editor for an online media company