The Ethnobotany of Eden

Rethinking the Jungle Medicine Narrative

Robert A. Voeks

• Publisher: University of Chicago Press
• Year: 2018
• Print ISBN: 9780226547718
• eBook ISBN: 9780226547855
• Topic: Biological Sciences
• Subtopic: Botany
• Index: Biological Sciences

In the mysterious and pristine forests of the tropics, a wealth of ethnobotanical panaceas and shamanic knowledge promises cures for everything from cancer and AIDS to the common cold. To access such miracles, we need only to discover and protect these medicinal treasures before they succumb to the corrosive forces of the modern world. A compelling biocultural story, certainly, and a popular perspective on the lands and peoples of equatorial latitudes—but true? Only in part. In The Ethnobotany of Eden, geographer Robert A. Voeks unravels the long lianas of history and occasional strands of truth that gave rise to this irresistible jungle medicine narrative.

By exploring the interconnected worlds of anthropology, botany, and geography, Voeks shows that well-intentioned scientists and environmentalists originally crafted the jungle narrative with the primary goal of saving the world's tropical rainforests from destruction. It was a strategy deployed to address a pressing environmental problem, one that appeared at a propitious point in history just as the Western world was taking a more globalized view of environmental issues. And yet, although supported by science and its practitioners, the story was also underpinned by a persuasive mix of myth, sentimentality, and nostalgia for a long-lost tropical Eden. Resurrecting the fascinating history of plant prospecting in the tropics, from the colonial era to the present day, The Ethnobotany of Eden rewrites with modern science the degradation narrative we've built up around tropical forests, revealing the entangled origins of our fables of forest cures.

ONE

God’s Medicine Chest

The world “is not round as they describe it,” proclaimed Christopher Columbus in his 1498 letter to his sovereign Queen Isabella, but rather “the shape of a pear which is everywhere very round except where the stalk is . . . like a woman’s nipple . . . [and it] is the highest and nearest to the sky . . . beneath the equinoctial line” (Columbus 1932 [1498], 30). Still confusing his encounter with the Americas as a shortcut to fabled India, Admiral Columbus was now ready to impart his latest geographical delusion—that the long-lost site of the biblical Garden of Eden lay perched “on the very top” of this earthly protuberance deep in the rainforests of Venezuela’s terra incognita. For Christians, Jews, and Muslims, Eden was imagined as an emerald paradise, blessed with a bounty of food and water, where the climate was forever balmy and spring-like. Flowers and fruit grew in abundance, including roses and violets associated with the Virgin Mary, and cherries symbolic of the Passion of Christ (Delumeau 1995, 123–127). It was also, as early biblical scholars and poets argued, brimming with healing plants—a vast and sacred pharmacopoeia of medicinal leaves and spices. The Garden of Eden was God’s medicine chest, and Columbus had located it squarely in the bosom of tropical America.

Columbus was certainly not the first to divine the physical location of Paradise, but he may have been the first to situate it in the equatorial latitudes. Indeed, before his first voyage of discovery, it had been assumed since the time of the ancient Greeks that the lands bordering the Equator were too scorched by the Sun to be inhabited by humans. Mesopotamia seemed a better choice, or perhaps Persia (Friedman 1981, 9–21). But Columbus thought otherwise. For evidence of his nipple hypothesis, he described how erosion driven by the fabled four rivers of Paradise had shaped the archipelago of islands off the northern coast of South America. He also drew on long-held ethnographic stereotypes of tropical lands and peoples, reasoning that at this low latitude in distant West Africa the people were black and the climate too hot for Paradise. In his favored South American Eden, however, the natives were lighter skinned, and “shrewder and have greater intelligence and are not cowards” (Morison 1963, 277–279; Columbus 1932 [1498], 32), sure signals in his imagination that the mythical Garden must be near at hand.

The quest for Eden in the tropical forest did not end with Columbus, and in so many respects, it has not ended yet. For those of us who were raised in the concrete jungles of the temperate latitudes, these distant sylvan landscapes of Africa, Asia, Oceania, and the Americas continue to conjure images rooted in legends and preconceptions of the misty past, oscillating from noble and harmonious to chaotic and terrifying. For some, they are habitats of glorious biological beauty, nature’s greatest evolutionary experiment expressing itself in magical and seemingly endless variety. Where else could surreally plumed resplendent quetzals ensconce in the trunks of dead trees, or rhinoceros hornbills haul their massive beaks and casques over the forest canopy, or birds of paradise perform their absurd dance of passerine passion? Where else could leaf cutter ants diligently tend their gardens of fungus, or caterpillars at one moment imitate squishy bird droppings and an instant later transform into a faux snake’s head, complete with ballooning forked tongue? Where else do rhinoceros beetles grow to the size of bullfrogs, or do miniscule frogs fail to reach the size of a tiny button? And where else do so many species of birds and bats and trees and insects coexist and co-depend in such a restricted patch of real estate?

Closely shadowing these biological narratives are homages to the rainforest’s fragile ecological harmony, plants and animals hopelessly intertwined through eon-aged, coevolved unions. Obscenely showy and aromatic flowers entice winged flower visitors, while succulent fruits lure sugar-craving birds and bats and monkeys. Green plants wage chemical warfare against the unending onslaught of herbivorous insects, while delicate symbiotic fungi form occult, subsurface networks of connections between rooted photosynthetic organisms. So specialized are some plants and animals in their behavior, and so mutually dependent are their food webs, that some researchers would describe these interactions as ecologically stable only so long as the individual elements of the system remain intact. Permit the extinction of one “keystone” species, many believe, such as a strangler fig or a specialized seed disperser, and the ecosystem experiences a domino effect of species loss, tumbling into simplified biological homogeneity. Add to these perceptions of forest instability the purported weakness and sterility of their soils, once cleared hardening into brick-red deserts of laterite, never again to sustain lofty evergreen forest, and the image of an equatorial earthly Eden, desperately in need of managerial intervention by well-intentioned outsiders, takes on a life of its own.

Images of native peoples and their forested homes are today as culturally constructed as they were in the time of Columbus. However primitive they may be technologically, indigenous people of the tropics are now most often depicted as noble stewards of their arborescent abodes, protecting their primordial homelands from the onslaught of loggers, planters, and cattle barons. Once derided as hairy-knuckled despoilers of useful tropical resources, eking out a meager subsistence through senseless slash-and-burn methods, indigenous forest folk are now seen as supremely adapted to the limitations imposed by the enervating climate and depauperate soils. Shifting cultivation (swidden) is now viewed as the most appropriate means of sustainably managing the forest and feeding families, and of contributing to the patchwork of successional habitats so crucial to species diversity. And the harvest of wild fibers and fruits and fuelwood for home and commerce is depicted increasingly by environmental scientists and aid agencies as a vital strategy for improving the nutrition and economic wellbeing of forest peoples, and encouraging meaningful forest conservation.

But there are other less sublime narratives forthcoming from tropical forests and fields, just as deeply ingrained, and just as culturally constructed. For while these landscapes manifest ecological wonder and protean biodiversity for some, for others they constitute landscapes of debilitating disease and nightmarish biotic afflictions. As the cradle of the planet’s most lethal arsenal of microbes—malaria, smallpox, Ebola, break-bone fever, Zika, and so many others—the equatorial latitudes have long been considered the “white man’s graveyard” as well as the merciless destroyer of untold millions of native peoples. Outside of the eradication of smallpox, most of these infectious maladies have proved immune to the efforts of Western biomedicine, afflicting twenty-first-century visitors and locals just as they did their millions of forebears.

The Jungle Medicine Narrative

Among the myriad stories and metaphors that have appeared over the centuries regarding the lands and peoples of the equatorial latitudes, none has proved more compelling in recent decades than the “jungle medicine narrative.” It’s a simple plot that evolved organically in the 1980s, with a compelling cast of heroes and villains, conflicts and noble causes. The story line goes something like this—tropical forests are pristine, largely unknown to science, and home to mysterious and wise native people who are privy to their great botanical secrets. Among these secrets are miracle-cure medicinal plants known and dispensed only by indigenous shamans and herbalists. Forest pharmacopoeias have the potential to cure society’s most horrific diseases, but they are imperiled by the forces of globalization as well as unsustainable harvest to meet distant commercial markets. The plot thickens with the entrance of antagonists, especially foreign pharmaceutical corporations and their ethnobotanist minions, who are hell-bent on pilfering and patenting these tropical treasures. Ask ten reasonably well-informed adults why we should be concerned with saving tropical forests, and half are likely to mention the impending loss of medicinal drug plants. “What a crime it is,” many will argue with passion, “that the world’s natural medicine chest is being destroyed before humans can rescue its wondrous medical miracles.” If this claim seems at all exaggerated, consider the pronouncement in a trade journal by a pharmacist and latter-day shaman that “besides being rich with an overpowering verdant fecundity and colorful wildlife, the rain forest holds secrets that could change the course of medicine as we know it” (Grauds 1997, 44). Or the words of a well-respected botanist, “Is it an impossible dream to hope that through medicinal plants the biodiversity of tropical forests might be able to save the world from cancer or AIDS and at the same time contribute to its own salvation?” (Gentry 1993, 21). Or a widely read ethnobotanist’s pronouncement that “I believe they [shamans] are our greatest hope for finding cures to currently incurable diseases (cancer, AIDS, the common cold)” (Plotkin 1993, 14). Such enthusiastic prophecies are less often forthcoming from scientists nowadays, but they continue to be deployed by environmental groups, New Age books, and websites. One recently stated that “if there is a cure to cancer or AIDS, it will be found within the rainforest’s biodiversity,” and that the Amazon region harbors “new drugs still awaiting discovery—drugs for AIDS, cancer, diabetes, arthritis and Alzheimer’s” (http://www.rain-tree.com/). Exaggerated, perhaps. But a host of useful and, yes, some miraculous medicinal drug plants have been uncovered in the tropical forests of Asia, Africa, and the Americas over the past few centuries, and these bioprospecting efforts have been going on more or less continuously since the early sixteenth century. But the pervasiveness of the jungle medicine narrative and its emotional resonance is a new phenomenon, having arrived and diffused rapidly throughout the developed and developing world beginning only in the 1980s. It has shaped a generation’s perception both of the value of tropical forested landscapes, and of the urgency to preserve them.

The Biochemical Factory

There are five fundamental and complementary features of the jungle medicine narrative (Myers 1984). Some are derived from ongoing research and hypothesis building in tropical ecology, biochemistry, and ethnobotany. Others find their inspiration in ancient theories and preconceptions regarding the relationship between nature and society. The first involves the biochemistry of green plants and fungi. Like other possible prey, plants and fungi are in more or less constant jeopardy of being consumed by predators, such as mammals, insects, bacteria, and just about every other life form. But being rooted in the soil, plants and fungi are at a distinct disadvantage compared to animal prey, which can simply run or fly or slither away. Responding to their immobile (sessile) disadvantage, rooted organisms (in fungi, these are hyphae) have developed various predator-avoidance strategies, including mechanical (load leaves and stems with cellulose and lignin), phenological (time biological functions to outwit herbivores), and biotic (provide food and shelter for good insects). A well-known example of the latter is the bullhorn acacia (Acacia cornigera), whose hollow thorns provide homes and miniature fat-protein nodules (Beltian bodies) give sustenance for colonies of carnivorous ants (Pseudomyrmex ferruginea). The acacia provides food and lodging for the ants, which for their part tenaciously attack insects or other animals (including humans) that threaten the tree.

Other plants and fungi have developed over time a complex arsenal of chemical defense mechanisms (Coley and Barone 1996; Sumner 2000, 107–123; Waterman and McKey 1989). These compounds, termed secondary compounds (or allelochemicals) because they appear to serve no primary metabolic function in the organism, include saponins, cyanogenic glucosides, tannins, phenols, alkaloids, isoprenoids, and others. Some of these, such as alkaloids, serve as toxicants against herbivory, whereas others like tannins act as digestive inhibitors. Others serve merely as feeding deterrents or pollinator attractants. Some use volatile compounds to help defend against a coterie of herbivorous assailants by “crying for help” with aromatic attractants. In this case, insect-eating birds, beetles, and other potential plant protectors are drawn by odor-plume distress calls put out by the plant to deal with one or another herbivorous attacker. Good for the plant; not good for the plant eater (Dicke 2010; Hare 2011).

People are not the intended target of these biochemical bulwarks, as most evolved long before humans or even our immediate ancestors appeared. But we are nonetheless intimately familiar with their properties. We encounter them with the chemical receptors on our tongues and noses every day, and in most instances, until we grow up and learn to respond otherwise, reject them readily (the gusto-facial reflex) as toxic and bad tasting (Hladik and Simmen 1996). But many are also, literally and figuratively, the spice of life—the source of the habanero chili’s fiery features, spearmint’s soothing taste and aroma, tea and coffee’s bitter flavor, and cilantro’s soapy consistency. They are why so few people can tolerate eating Brussels sprouts (due to phenylthiocarbamide), and why so many are passionate about chocolate (theobromine). And they are why we enjoy our potatoes boiled, mashed, and French-fried, but never raw (to eliminate glycoalkaloids and proteinase inhibitors) (Johns 1990, 69–70).

Among this armada of plant-derived defensive compounds, alkaloids are particularly relevant to the jungle medicine narrative. They are numerous, new ones are being discovered daily, and they are frequently bioactive—that is, they have positive or negative biochemical effects on humans. In 1950 there were about 1000 known alkaloids; by 2008, the number had burgeoned to over 21,000 (Raffauf 1970; Wink 2008). Their primary evolutionary role is to repel the attacks of plant or fungi eaters, but their bitter-tasting toxicity often produces marked effects on biochemical activities inside the human body, particularly disruption in the brain and nervous system (neurotoxicity) and disruption of cell membranes (cytotoxicity) (Wink and Schimmer 1999; Wink 2008). Many alkaloids have a lengthy legacy of recreational consumption for their stimulating properties, such as caffeine from coffee and tea, nicotine from tobacco, cocaine from coca leaves, and ephedrine from Mormon tea. Others are employed for their soporific effect, such as morphine from poppies, while others, such as capsaicin in chilis, are consumed for their wonderfully painful burning sensation, what psychologists refer to as a “thrill seeking” flavor (Rozin and Schiller 1980). Some intoxicating alkaloids help us communicate with our gods through hallucinogenic visions, such as psilocybin in Psilocybe spp. mushrooms, and harmine in Amazonian ayahuasca vines (Banisteriopsis spp.). Still others stir our passions, or at least we think they do, such as atropine from the massive root of mandrake (Mandragora officinarum), the infamous “love root” for early Persians, and the “testicles of the demon” for medieval Arabs (J. Mann 2000, 21–27; Simoons 1998, 101–134). Atropine is also contained in deadly nightshade (Atropa belladonna), which was administered by medieval women to their eyes to dilate their pupils and thus appear more sexually alluring (M. R. Lee 2007). We also employ alkaloids to hunt and to harm our enemies, in convoluted pathways that reveal the complexity of plant and animal relationships. Take the case of garishly colored Central and South American poison arrow frogs (dendrobatids), whose powerfully toxic skin alkaloids have long been employed to toxify arrows. These poisonous frogs don’t manufacture their own poisonous alkaloids, however, but rather assimilate them from the arthropods they consume, certain ants and beetles (Choresine spp.) and the occasional millipede. These in turn acquire them by eating other plant-eating insects (V. Clark et al. 2005; Dumbacher et al. 2004). Thus, poisons that are deployed originally by green plants to do battle with one or another plant-eater manage to ascend through the food chain, arriving finally on the pointed projectiles of skilled Amazonian hunters.

Tropical forests became central to the evolving jungle medicine narrative with the discovery in the 1970s of a curious geographical dimension to the distribution of secondary compounds. Most occur in the tropics. And while it is true that these compounds occur in plants at all latitudes (about 20% of all flowering plants contain alkaloids) (Wink 2008), a significant inverse relationship exists between the proportion of a native flora that tests positive for alkaloids and the average latitude of the country. Thus, the native plants in mid-latitude countries like the United States and New Zealand register only 13.7% and 10.8% alkaloid presence, respectively, whereas countries closer to the Equator, such as Kenya and Ethiopia, register 40.0% and 37.2%, respectively (Levin 1976). Studies of individual plant groups yield similar results. For example, along a climatic gradient from temperate to tropical eastern Australia, five eucryphia tree species (Eucryphia spp.) exhibit increasing plant chemical defenses (phenols and tannins) against herbivory (Hallam and Reid 2006). In this case, the lower the latitude, the higher the proportion of species containing allelochemicals. This compound gradient, from temperate to tropical latitudes, is illustrated nicely by the altitudinal vegetation transition present on the island of New Guinea. Located in the far western Pacific Ocean, only 5–6 degrees south of the Equator, the island (covering the Indonesian states of West Papua and Papua, and the country of Papua New Guinea) presents a dramatic vegetation gradient from swampy mangroves at sea level through dense tropical forests in upslope areas to windswept alpine meadows on 4509 m (14,793 ft) Mt. Wilhelm. In this insular microcosm of a temperate to tropical climate transition, subalpine forest and alpine grassland each maintain 0% alkaloids in their respective floras, whereas lowland and montane rainforest maintain 21.5% and 14.6% alkaloid presence, respectively (Hartley et al. 1973). Alkaloids, it seems, like the rainforest. But why is this so?

The most reasonable explanation for this high-to-low latitude chemical defense transition is increasing levels of predation in species-rich tropical habitats, or the biotic interactions hypothesis (Coley and Aide 1991; Lim et al. 2015). Predator-prey and other species-species interactions, at various levels of the food chain, are simply more intense in the tropics than in other biomes. For example, ants appear to attack wasp larvae with increasing frequency along a latitudinal gradient towards the Equator. And bird’s nests in the tropics experience significantly higher predation pressure than those in temperate regions (Schemske et al. 2009). Leaf consumption by insects is higher in tropical than temperate areas, as is the infection rate of plants by endophytic fungi (most of which benefit the plant) (A. Arnold and Lutzoni 2007). And the density and diversity of insects (butterfly larvae and others) feasting on two species of wild pepper (Piper aduncum and P. aequale) increases along a gradient from higher to lower latitudes. But because these two species do not exhibit greater leaf damage near the Equator, individual plants must have better antiherbivore defenses in lower latitudes (Salazar and Marquis 2012). In summary, tropical plants more so than their temperate zone counterparts marshal an assemblage of chemical defenses, including alkaloids, phenols, and many others, to repel insect, fungal, microbial, and other attackers.1 Over thousands of years, people have learned to exploit many of these compound-rich plant parts, especially roots, bark, and leaves, where most of these toxins are stored, to produce a veritable cornucopia of healing and intoxicating formulas.

The significance of this high to low latitude biochemical gradient in the search for drug plants is enhanced exponentially by the legendary biological diversity of moist tropical forests. Mantling only 7 to 8% of the Earth’s surface, these arboreal habitats sustain one-half to two-thirds of the estimated 300,000–450,000 plant species on Earth (Mora et al. 2011; Pimm and Joppa 2015). A survey of the trees in a one-hectare plot (100 m × 100 m, about 2.5 acres) in old-growth tropical forest, for example, is likely to yield over 200 adult tree species. In Brazil’s Atlantic Coastal Forest (roughly 13° S), a single one-hectare plot revealed a remarkable 450 tree species (Anonymous 1993). Compare this to the meager list of tree species on my own forested, five-hectare property in northern Oregon (45° N)—Douglas fir (Pseudotsuga menziesii), ponderosa pine (Pinus ponderosa), Oregon white oak (Quercus garryana), bigleaf maple (Acer macrophyllum), and a few scraggily red alders (Alnus rubra)—and the enormity of this biodiversity bonanza looms large indeed. A comparison of the difference ...

Table of contents

• Cover
• Title Page
• Copyright Page
• Dedication
• Contents
• Preface
• chapter one  God’s Medicine Chest
• chapter two  Terra Mythica
• chapter three  People in the Forest
• chapter four  Green Gold
• chapter five  Weeds in the Garden
• chapter six  Gender and Healing
• chapter seven  Immigrant Ethnobotany
• chapter eight  Forgetting the Forest
• chapter nine  Environmental Narratives
• Notes
• References
• Index