“Campfires and other types of fires, like hearth fires, seem to be multi-sensory stimulators, so they grab our attention through every single one of our senses,” says University of Alabama anthropologist Christopher Lynn, who authored the study. Maybe that’s why the silence between me and Mo in those early days never felt awkward — because the scene around us was already absorbing enough. We were comfortable in those quiet moments, just observing the crackling of the flames and the endless smoke that curled into the evening sky.

There’s also the fact that humans are seemingly wired to gather around fires at night, a practice that stretches far back in the history of our species, explains Matt Rossano, an evolutionary psychologist at Southeastern Louisiana University. Early on, when fires were most often built of necessity rather than for entertainment, the people who maintained them had to cooperate in order to enjoy fire’s benefits: warmth, protective light, the ability to cook food. And these days, though their purpose may have changed, fires remain a tool of cooperation, Rossano says, often fostering conversations that are relaxed and emotionally positive.