All of these changes might take a toll on some heterosexual relationships. Fairbairn argues that some women, who might currently feel the need to “dumb themselves down” to attract insecure men, may no longer need to. In some cases, this scenario is already playing out. Her 30-something daughter, for example, has been on disaster dates in which the man is clearly looking for an ego boost. But she is capable, active and has a doctoral degree, and “she refuses to pretend that she doesn’t do home renovations and regularly runs 50 miles (80km), just so a guy will think she’s sexy,” Fairbairn says.

Strength is one of the few ways that men, on average, exceed the abilities of women – but if that changed, it would in fact be a continuation of the way that male identity and 'traditional' masculinity is already being challenged in the real world. In the past 50 years, women have become more independent and, in many cases, have overtaken men in earnings, achievements and success. Technology is also muting gender differences, making historically male-dominated fields such as manufacturing and the military open to women, who can now rely on intellect and hand-eye coordination rather than upper body strength, for example, to build cars or engage in combat.

As a result, some men cling to their gender’s generally greater capacity for physical power as justification that “somehow, men are still more entitled to power,” argues Jackson Katz, an author, lecturer and president of MVP Strategies, a company that provides training and education on gender violence prevention. “As women have started competing with men in areas that men had historically excluded them from, some men have retreated into this world where physical size and strength matters even more, because it’s the one area where they continue to hold advantage over women.”

Katz argues that this might help to explain some of the popularity and growth of American football, boxing, MMA and other violent sports. “A man might not be able to understand or articulate this, but the thinking comes down to, ‘Yes, a woman may make more money than me, my boss might be a woman, my wife might have better job than me, but none of them can play football,’” Katz says. He notes, though, that obsession with gladiator-type masculinity tends to be a predominantly American phenomenon.