This summer, I, like so many other Americans, have forgotten what it means to be dry. The heat has grown so punishing, and the humidity so intense, that every movement sends my body into revolt. When I stand, I sweat. When I sit, I sweat. When I slice into a particularly dense head of cabbage, I sweat.
The way things are going, infinite moistness may be something many of us will have to get used to. This past July was the world’s hottest month in recorded history; off the coast of Florida,
Our aversion to sweat doesn’t make much evolutionary sense. Unlike other excretions that elicit near-universal disgust, sweat doesn’t routinely transmit disease or pose other harm. But it does evoke physical labor and emotional stress—neither of which polite society is typically keen to see. And for some, maybe it signifies “losing control of your body in a particular way,” says Tina Lasisi, a biological anthropologist at the University of Michigan. Unlike urine or tears, sweat is the product of a body function that we can’t train ourselves to suppress or delay.
We also hate sweat because we think it smells bad. But it doesn’t, really. Nearly all of the sweat glands on human bodies are of the so-called eccrine variety, and produce slightly salty water with virtually no scent. A few spots, such as the armpits and groin, are freckled with apocrine glands that produce a waxy, fatty substance laced with pheromones—but even that has no inherent odor. The bacteria on our skin eat it, and their waste generates a stench, leaving sweat as the scapegoat. Our species’ approach to perspiration may even make us “less stinky than we could be,” Best told me. The expansion of eccrine glands across the body might not have only made our skin barer; it’s also thought to have evicted a whole legion of BO-producing apocrine glands.
As global temperatures climb, for many people—especially in parts of the world that lack access to air-conditioning—sweat will be an inevitability. “I suspect everyone is going to be quite drippy,” Kamberov told me. Exactly how slick each of us will be, though, is anyone’s guess. Experts have evidence that men sweat more than women, and that perspiration potential declines with age. But by and large, they can’t say with certainty why some people are inherently sweatier than others, and how much of it is inborn. Decades ago, a Japanese researcher hypothesized that perspiration potential might be calibrated in the first two or three years of life: Kids born into tropical climates, his analyses suggested, might activate more of their sweat glands than children in temperate regions. But Best’s recent attempts to replicate those findings have so far come up empty.
Read: The man who did not sweat
Perspiration does seem to be malleable within a lifetime. A couple of weeks into a new, intense exercise regimen, for instance, people will start to sweat more and earlier. Over longer periods of time, the body can also learn to tolerate high temperatures, and sweat less copiously but more efficiently. We sense these changes subtly as the seasons shift, says Laure Rittié, a physiologist at Glaxo-Smith Kline, who has studied sweat. It’s part of the reason a 75-degree day might feel toastier—and perhaps sweatier—in the spring than in the fall.
But we can’t simply sweat our way out of our climatic bind. There’s a ceiling to the temperatures we can tolerate; the body can leach only so much liquid out at once. Sweat’s cooling power also tends to falter in humid conditions, when liquid can’t evaporate as easily off of skin. Nor can researchers predict whether future generations might evolve to perspire much more than we do now. We no longer live under the intense conditions that pressured our ancestors to sprout more sweat glands—changes that also took place over many millions of years. It’s even possible that we’re fast approaching the maximal moistness a primate body can produce. “We don’t have a great idea about the outer limits of that plasticity,” Jason Kamilar, a biological anthropologist at the University of Massachusetts at Amherst, told me.
For now, people who are already on the sweatier side may find themselves better equipped to deal with a warming world, Rittié told me. At long last: Blessed are the moist, for they shall inherit the Earth.
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