Get the Popular Science daily newsletter💡 Somewhere between 9,500 and 9,900 years ago, three Scandinavian teenagers were hanging out, chewing gum after a meal. Specifically, they were chewing pitch or tar made from the bark of birch trees. Many millennia removed, archaeologists analyzed the spit out wads and discovered what the teens had recently eaten (red fox, hazelnut, deer, and apple), as well as the state of their oral health (poor). The findings were published in the journal Scientific Reports in  2024. It’s among the earliest known examples of chewing gum in the archaeological record, but it’s far from the only one.  Humans  have been gnawing on rubbery bits of indigestible gunk for a long, long time. Gum chewing independently arose across different cultures and regions at different times, says Jennifer Mathews, an anthropologist at Trinity University in San Antonio, Texas. In Mexico, for instance, Mayans and later Aztecs chewed chicle, a substance derived from the milky latex of the tropical sapodilla tree. Chicle ultimately led to the creation and commodification of the modern chewing gum we know today, as described in Mathews’ 2009 book, Chicle: The Chewing Gum of the Americas, From the Ancient Maya to William Wrigley.  Aztecs also chewed natural bitumen, a petroleum-based material similar to asphalt that often washes up on shorelines, sometimes on its own and sometimes mixed with chicle. It was a central enough part of Aztec culture that they wrote up rules for it. It was considered uncouth for anyone besides young children or elderly women to chew it publicly, says Mathews. Elsewhere, people chewed on gums derived from plants like mastic in ancient Greece–which became the root of the word mastication–terebinth resin in Central Asia, or spruce gum among Indigenous Americans.  “They’re using what they have in their environment to fix a problem,” says Mathews. Clearly, as it showed up so many times in so many places, gum served a need.  Why we chew In the absence of toothpaste and dentists, people found their own ways to keep their mouths feeling as hygienic as possible. Chewing gum filled in some of those gaps and its primary purpose across cultures was to clean the teeth, freshen the breath, and boost oral health, Mathews explains. Mastic and chicle alike are commonly described as having pleasant, sweet, and piney or woodsy flavors– probably a preferable smell and taste to whatever bits of food might linger between the teeth after meals. Today, sugar free gum can offer some smile benefits, according to the American Dental Association (though overdo it and you could end up with a jaw disorder). [ Related: Can chewing gum reshape your jawline? We asked experts. ] But that’s not the only reason for our enduring love of gum. Chewing on it also likely helped people stave off hunger and thirst when food and water weren’t readily available, Mathews adds. Some research now demonstrates that gum chewing suppresses appetite and leads people to eat less than they would otherwise. Chewing gum may also confer cognitive benefits, according to a handful of psychology and scientific studies. In certain settings, it seems to boost test performance, working memory, and alertness. Some research has also found that gum chewing can help manage stress and anxiety, though other research has found contradictory results and it’s worth noting that a few of the affirmative studies were funded in part by gum manufacturers. Gum goes global In fact, all of the above has been used to market gum, as far back as World War I. William Wrigley Jr, founder of the namesake company, convinced the U.S. military to include gum with soldiers’ rations to help with teeth cleaning, nervousness, and hunger management. Through deployed soldiers, more and more people were exposed to gum as a commodity item. “That’s really one of the reasons chewing gum spread around the world. [In the modern era], it really started out as an American habit,” says Matthews. The first mass-manufactured, flavored gums were made from chicle in the 19th century. Thomas Adams, a Staten Island inventor, was approached by Antonio Lopez de Santa Ana, a former president of Mexico living in exile. Lopez de Santa Ana hoped to harness Adams’ skills to derive a material from sapodilla trees that could compete with Charles Goodyear’s rubber. But after several failed attempts and experiments, Adams settled on selling chicle gum with added flavoring to candy stores instead, Mathews says.  In 1871, Adams patented a gum-making machine and began selling his product under the Black Jack brand. As chewing gums grew in popularity, meeting the demand through chicle alone became increasingly tough. Sapodilla trees are slow growing and temperamental in their latex production. “If you over-tap it, it will basically dry out,” Mathews explains.  Plus, chicle is a difficult and dangerous product to harvest, requiring workers to scale trees, score bark, and collect latex over large areas of forest. Around the 1950s, Wrigley began looking for other natural sources of gum, but didn’t find anything to match the quality and quantity of chicle. Instead, gum makers turned to synthetics–or in other words: plastic.  The unfortunate downside The vast majority of commercially available gums are now made from different blends of synthetic, petroleum-based polymers. Polyethylene (also used to make plastic bags and bottles), butyl rubber–the material bike inner tubes are made from, and polyvinyl acetate (PVA), which is a key ingredient in many glues can all be found in some gums. Softeners, waxes, flavorings, and other additives are also part of the mix.  As you might guess, chewing on macroplastic can be a source of microplastic ingestion. A preliminary study presented at the American Chemical Society’s (ACS) spring meeting in March found that a single stick of gum releases hundreds of teeny polymer bits as it’s chewed. An unrelated 2016 study found that gum chewing is a significant source of phthalate exposure. Phthalates are chemicals used to increase the flexibility and durability of plastics. Exposure to high amounts , especially for pregnant women and young children, carries well-established health consequences like increased risk of preterm birth and asthma.  It’s not yet known exactly how microplastics behave in the human body nor what health impacts they carry. Avoiding exposure is nearly impossible, given that microplastics are increasingly present in the air, water, and food we rely on, and they have shown up in basically every human tissue tested. However, willingly gnawing on plastic can still feel like an unsettling choice. For her part, Mathews switched largely from synthetic gum over to the naturally-derived, more niche products still available while she was working on her book years ago.  Unfortunately, even natural wax and chicle-based gums still seem to contain and confer plastic contamination, according to the recent ACS research. “Both synthetic and natural gums had similar amounts of microplastics released when we chewed them,” one of the researchers wrote in a statement. Despite the knowledge, history can be hard to escape. I’ve gone through two sticks of gum while writing this article. This story is part of Popular Science’sAsk Us Anything series, where we answer your most outlandish, mind-burning questions, from the ordinary to the off-the-wall. Have something you’ve always wanted to know?Ask us.