Consider the sweet, intoxicating smell of a rose: While it might seem superficial, the bloom’s lovely odor is actually an evolutionary tactic meant to ensure the plant’s survival by attracting pollinators from miles away. Since ancient times, the rose’s aroma has also drawn people under its spell, becoming one of the most popular extracts for manufactured fragrances. Although the function of these artificial scents has varied widely—from incense for spiritual ceremonies to perfumes for fighting illness to products for enhancing sex appeal—they’ve all emphasized a connection between good smells and good health, whether in the context of religious salvation or physical hygiene.
Over the last few millennia, as scientific knowledge and social norms have fluctuated, what Westerners considered smelling “good” has changed drastically: In today’s highly deodorized world, where the notion of “chemical sensitivity” justifies bans on fragrance and our tolerance of natural smells is ever diminishing, we assume that to be without smell is to be clean, wholesome, and pure. But throughout the long and pungent history of humanity, smelling healthy has been as delightful as it has disgusting.
The desire to surround ourselves with ambrosial fragrances can be directly traced to the unavoidably rank smell of unwashed humans, and to get to the root of body odor, you have to start with sweat. According to journalist Sarah Everts, who’s conducted extensive research on the science of perspiration, human sweat by itself typically barely smells at all. “The problem is that bacteria living on our body like to eat some of the compounds that come out in our sweat,” she says. Eccrine glands all over the body and apocrine glands found mostly in the armpit and genital areas secrete various compounds that are consumed by bacteria, which in turn release molecules with a smell we recognize as body odor. “In particular, it’s one kind of bacteria called Corynebacterium, and they make a molecule which is really a top note of human body odor,” Everts says. “It’s called trans-3-methyl-2-hexenoic acid.”
Of course, humans were unaware of such compounds throughout most of recorded history, which is why the first efforts to smell civilized consisted of smothering the odors with more favorable scents.