On June 6, 1800, nearly a year into his scientific journey through South America, Alexander von Humboldt arrived at a mission on the Orinoco River called La Concepción de Uruana. It was a stunning site. The village sat at the foot of granite mountains, amidst huge pillars of stone that rose above the forest. Weeks before, Humboldt had seen mysterious etchings on the summits of such rocks—painted, the natives told him, by ancestors carried up there by the waters of a great flood.
Although weakened by bouts of fever and hunger, Humboldt was in fine spirits. In the preceding months he had watched the Leonid meteor shower fill the sky, experienced his first earthquake, and confirmed the communication of the Orinoco and the Amazon rivers through the Casiquiare Canal. He had collected electric eels and watched the dissection of a manatee. If at times the mosquitoes were so thick as to obscure the horizon and prevent his reckoning of latitude, or if other times ant hordes filled his canoe, he pushed on, spurred, he wrote, by an uncertain longing “for what is distant and unknown.”
Humboldt and his botanist companion Aimé Bonpland (and Indian servants, and pressed plants, and jars of preserving spirits, and a chattering menagerie of birds and monkeys in cages on his boats) stayed at Uruana for only one day, conversing with the missionary Fray Ramon Bueno and visiting the Otomac villagers. For all of nature’s splendors, it was the people of Uruana that most caught Humboldt’s attention: “a tribe in the rudest state,” “considered dirty even by their neighbors,” “ugly, savage, vindictive, and passionately fond of fermented liquors,” and yet presenting “one of the most extraordinary physiological phenomena” Humboldt had ever seen. The Otomacs ate earth, “a prodigious quantity” of it. During the two to three months of the rainy season, when the high and turbulent waters of the river made fishing difficult, they claimed to eat nothing but.
Four years after his return, in the first edition of Aspects of Nature, published in 1808, Humboldt described the particular qualities of the earth, called poya: “a soft, unctuous clay, a true potter’s clay, of a yellowish-gray color,” gathered from specific sites along the Orinoco’s banks. And while Humboldt didn’t watch the Otomacs eat poya himself, he observed the great stores of clay balls that they had provisioned for the winter.
By then, Humboldt was one of the most famous men in Europe, and his report of this peculiar habit didn’t go unnoticed. “This claim has become the subject of a lively dispute,” he wrote, and to bolster his assertions, he cited other examples reported from across the torrid zone: the caouac clay eaten by the “Negroes of Guinea,” the mud cakes called tana ampo sold in Javan markets, the fist-sized pieces of friable steatite loved by the natives of New Caledonia. He had seen women on the banks of the Magdalena River eat their potting clay. Wolves, he wrote, ate clay in winter.
However lurid, the story was more than just a traveler’s yarn about the savages. Humboldt noted natives eating millipedes, Marimonda monkeys, gum resins, ants; he diligently reported stories of cannibalism. But none raised the same physiologic speculation. “Tell me what you eat, and I shall tell you what you are,” wrote Anthelme Brillat-Savarin, in 1825, the year that the final volume of Humboldt’s Travels was published in France. Indeed, we have long defined ourselves and others by what we do and do not eat, from kashrut dietary restrictions described in Leviticus to the naming of Comanche bands (Kotsoteka—buffalo eaters, Penateka—honey eaters, Tekapwai—no meat) to insults—French frogs, English limeys, German krauts. But poya seemed to beg a different question: what was one to make of people who ate food that wasn’t food at all?
“Is earth capable of being assimilated?” asked Humboldt. “Or is it simply ballast for the stomach, to appease hunger? These are questions I cannot answer.”