In times of mourning, people wear black. On Wednesday, stunned Clinton supporters — many who wore white to polling stations in a symbol of suffragist solidarity — took to social media to post photos of themselves wearing black, variously grieving the election results, the demise of the American dream, and the loss of humanity.

Why did this intuitively feel like an appropriate response to Tuesday’s events? The origins of this dark symbolism are deeply historical and psychological, rooted in the things that we just don’t understand.

We have the Romans to thank for kicking off the all-black tradition. Grieving families would don dark-colored toga pullas, thought to be a nod to the link between blackness and the unknown. Not that the unknown was necessarily a positive or negative thing: Darkness was a mystery that was beyond human comprehension, much like the wisdom of the gods, as historian Ellen Conroy wrote in The Symbolism of Colors in 1921. She noted that the ancient Egyptians had come to similar conclusions: “In Egypt, Kneph the Creative Mind was sometimes addressed as ‘Thrice unknown darkness transcending all intellectual perception,’” she wrote, “for certainly the wisdom of God is beyond the comprehension of human intellect.” Our feelings about death, incomprehensible and inextricably linked with the unintelligible will of God (or gods), was conveniently summed up in a single non-hue.

The association stuck, manifesting in the dark clothing trend revived by mourners in Europe during the Middle Ages, the Victorian Era, and at least up until World War II. While society’s adherence to those traditions have tapered off slightly since then, the impossible whys and hows surrounding death, whether of people or cherished ideals, remain a mystery befitting of the deepest, darkest black.

While the classic reason to wear black is an acknowledgment of those we mourn, the practice took a turn on Wednesday morning. It served a practical reason, signaling to the people around us what we don’t have the energy to say. “Black is also meant to silence the things that are not to be revealed to everyone the thoughts that lie too deep for tears, the innermost and most sacred experiences of life,” Conroy wrote. The people around us know how we feel — and perhaps acts as an invitation for them to mourn with us too.

The symbolic associations we’ve made between black, mystery, and mourning are taken for granted now in Western societies, giving way for psychologists to try and make sense of what else it has come to represent. A study in Applied Cognitive Psychology hypothesized that because we “usually associate the colour black with evil, aggression and badness,” suspicious people who wear it are perceived as more aggressive than those dressed in lighter shades. Yet another study, published in the journal Policing in 1997, suggested that police officers dressed in black were perceived as more favorable than those wearing lighter uniforms.

All this is to say that these days, the influence of black clothing on the perceiver has a lot more to do with what the perceiver thinks of the person wearing black. Accordingly, in 2014, a review in the Annual Review of Psychology gave credence to the idea that color has effects on our “affect, cognition, and behavior” but taking care to set “boundary conditions, moderators, and real-world generalizability” was necessary for anyone attempting to make those claims.

Clinton supporters are wearing black to symbolize their grief, but how that blackness will affect how people view them depends on who you ask. Some will condemn them, like the dark-clothed suspects; others will see them as familiar friends, like the classically uniformed police officers. Either way, the black-clad among us are continuing a long human tradition of showing solidarity and grief — and acknowledging what we cannot understand.

Photos via Getty Images / Justin Sullivan

Yasmin is a writer and former biologist living in New York. A Toronto girl at heart, her writing also appears in The Last Magazine and SciArt in America. You might recognize her as a past host of Scientific American's YouTube series.