Before the beard trend, I preferred the look of a clean-shaven man. Then beards went mainstream. Now, after seeing countless men donning this look, I find myself giving five o’clock shadows a second glance. Apparently, I’m not alone.

“I find men with beards more attractive. Before it was not important, but now half of the men I know have beards,” one survey respondent told The Guardian when asked about facial hair.

It’s often thought that we are hardwired by millennia of natural selection to gravitate towards certain traits, like facial symmetry. We know our standards of beauty change over time – but those shifts have been thought to be relatively long-term, responding to the media and popular culture. And even if we know that our sense of beauty still differs somewhat from person to person, most of us believe that we each have a certain ‘type’ that stays somewhat constant throughout our lifetime.

But it turns out ‘over time’ is a shorter window than it once was. Our standards of beauty don’t just change over months or years. They can change in an instant.

You might also like:

• The benefits of having a babyface

• The myth of universal beauty

• The surprising downsides of being drop dead gorgeous