Perhaps the Indians roasted them like s'mores—rotating them ever so slowly to make sure every side got just dark enough, but not so long that they caught on fire. Or maybe they went all out, expediting the process and blowing out any flames. Of course, for the art of hovering a rubber-coated foot over a fire, one's pain tolerance may have ultimately determined how long the process went on.

From the Amazonian Indians' pain, modern society may have gained the rubber boot. That's the best guess, anyway, of experts who know their latex. "When the New World was discovered by Columbus and his followers, one of the first things they found was rubber," says Joe Jackson, author of The Thief at the End of the World: Rubber, Power, and the Seeds of Empire. "There were two things reported back: bouncing balls and boots."

Indians would go out and slice into the bark of a rubber tree, collecting the white latex sap in a process similar to tapping maple syrup, Jackson explains. Then they would turn to the fire. "And, for hours, they would just sit there turning this stick over a smoky fire," he says. "Then they would take a cup from a bigger basin of latex and pour more on the stick until they had a black ball of rubber," to be sold for or used in games.

This long and laborious process must have gotten dull, Jackson speculates. "They may have tried dipping different things, including their feet, into the rubber."

Whether or not this boredom was the inspiration, historians do believe that Indians created makeshift boots by hanging their rubber-coated feet over fires. "It may have taken an awful lot of will power," Jackson guesses. "Maybe they dipped them in until they couldn't stand it anymore. Took a break. Then dipped them back in."

The result was a crude form of what would later evolve into high men's fashion, a farmer's standard, and a kid's rainy day footwear. None of them would come until centuries later, however, after Charles Goodyear improved on the Amazonian technology.

"Goodyear was obsessed with rubber," says Chris Laursen, the science and technology librarian for the Rubber Division at the University of Akron, a professional organization for the rubber industry within the American Chemical Society. "He foresaw a world in which everything was made out of rubber."

Before he could make that world a reality, Goodyear first needed to find a way to keep rubber from cracking in the cold and melting in the heat. The solution came to him by accident in 1839, according to his own book, Gum-Elastic and Its Varieties. Goodyear spilled a concoction of rubber, sulfur and white lead onto a hot stove and witnessed the mixture charring around the edges but, surprisingly, not melting.

In this eureka moment, Goodyear managed to cross-link rubber molecules via sulfur bridges into one large macromolecule—creating a stronger, more thermal-resistant material. "Under a powerful microscope," Laursen says, "it would look like a cooked plate of spaghetti all intertwined." Goodyear would later fine-tune the process and coin it "vulcanization," after the Roman god of fire.

As for the indigenous Amazonians, exactly how they used their boots remains a mystery: Were the boots disposable, molded on before a journey into the wet forest? Or could they be peeled off and worn again?

Unfortunately, Jackson says, "no chroniclers ever wrote about that. They often wrote about the ball games [the Indians] played, but never how those [rubber] balls were formed."