We have selected a few examples of the complex convergences of biology, ingenuity, faith and circumstance that have led to discoveries of new species and new applications. Although this volume primarily focuses on plants and natural products that are used medicinally, we have also included several foods in this section to help illustrate the chemical sophistication of ethnobotanical information in some cases, and its surprising familiarity in others.
At some point in the history of human habitation in the Andes a connection was made between malarial fevers and an infusion from the bark of Cinchona trees. Before the first shipments of'Jesuit bark' to Europe and prior to the alleged cure of the visiting Countess of Chinchón, the profound effects of Cinchona bark were recognized and put to use. Speculation has woven an image of a large tree downed by a storm, lying in a stagnant pool of water. Over time the water grew brown from the bark and other plants that had fallen into the pool. A traveller, feeling weak and ravaged by intermittent fevers, stopped to drink and quench his thirst. A short time later the fever went into remission. There were few enough variables and so the survivor was able to connect the disappearance of the fever with the tea-colored water and the peeling bark of a dead tree. In such a way the bark of the Cinchona tree gained recognition as a treatment for malaria, a disease that has caused the death of more people than any other in history (Jaramillo-Arango, 1950).
The uses of most plants are not as well established as Cinchona, but are undergoing constant revision and development. The tomato (Lycopersicon esculentum), now among the top 30 food crops in the world, only relatively recently overcame a reputation of being a rank and toxic weed (National Research Council, 1989). Its origins can be traced to the Andes, but there are no indications that it was used as a food there. Tomatoes were introduced to Europe by 1530, but spread more as ornamentals and curiosities than as a food. For centuries the 'love apple' was widely believed to be poisonous, it was considered suicidal to eat one raw. This probably has some founding in past experience, as many other members of the Solanaceae, jimson weed (Datura), tobacco (Nicotiana) and nightshade (Solanum spp.), can be highly toxic (Blackwell, 1990). The fruits first gained acceptance as a food in Italy, but northern Europe and North America continued to regard it with suspicion until the late 1800s. In a popular American housekeeping guide published in 1860, readers were still cautioned to cook tomatoes for at least 3 hours prior to their consumption (National Research Council, 1989). As recently as 1962 a species that was new to science was discovered in Peru. These tiny, green tomatoes contain twice the sugars of the commercially cultivated species. After nearly a decade of crossbreeding the genes for a high sugar content were successfully transferred into horticultural lines of the standard tomato (National Research Council, 1989). Previously shrouded in either misrepresentation or obscurity, the tomato is an example of potentially valuable plants and genes that go unknown or underappreciated.
The discovery of many ethnobotanical applications do not rest on a single experience such as a fatal bite or a miraculous cure. Often edibility or therapeutic applications can require elaborate advance preparations. Two types of manioc, for example, are widely cultivated and consumed but require specific and laborious preparations. The two varieties, 'bitter' manioc and non-toxic 'sweet' manioc, appear so similar that they are only recognized as one species, Manihot esculenta, by Western botanists (Schultes, 1992). Failure to recognize the difference, however, could prove fatal.
Bitter manioc, a root crop that is a staple starch for many people in South America, contains levels of cyanide that can cause death (Lewington, 1990). The Kuikuru of the Central Amazon cultivate only the more toxic bitter manioc and have developed a distinctive preparation process that renders the tuber edible.
The tubers are first washed and the outer layers, containing most of the toxin, are scraped off using shells. After being peeled they are grated into a watery pulp to remove the toxin. Other groups begin by soaking the tubers for 3 or 4 days and then mash or pound the semi-fermented mass. They then strain the pulp without rinsing, unlike the Kuikuru who rinse it thoroughly at this stage by laying the grated tuber on wood slats and pouring water over the top (Dole, 1978). The resultant leached pulp, the liquid and the starch are all used as food: soups, beverages, sauces, flour and flatbreads. When a hot soup is made from the liquid pressed from the pulp a man is designated as the formal taster, ritually taking responsibility for any toxicity on behalf of the host. Numerous accounts of its use as a poison for both suicide and homicide provide further evidence of the awareness of the toxin. At some point multiple experiments in distinguishing and preparing bitter manioc root established the necessary steps that continue to be followed daily in many parts of South America and Africa (Dole, 1978).
Some applications require combining two or more species to produce the desired result. Many types of curare, or arrow poisons, have been devised using species of Chondodendron vine from the forests of the western Amazon, woody Strychnos vines from the Orinoco basin and Guianas, and a combination of gums and resins that help adhere the poison to the tip of an arrow or dart. As mentioned earlier, taste is often one of the principal tests of the identity and potential of a plant. It is probable that the characteristic bitterness of many plants used as arrow poisons may have led hunters to discover their poisonous attributes (Schultes, 1992). The range of arrow poisons used across South America are known by many names: curare, wourali, ourari, urali. Similar sounding names may be evidence of the frequent exchange of ideas and ingredients among mobile hunters. One could deduce then that the initial discovery of eflicacy, or any subsequent incremental improvements, travelled along these same channels of communication. This information has persisted in the traditional rituals of harvest, preparation and use. Over 75 different plant species are used to make arrow poisons in the Colombian Amazon alone, but the majority have been found to contain at least one of the two genera mentioned above (Schultes and Rauffauf, 1992).
Another combination of lianas, or vines, is used to make an intoxicating drink manufactured for ritual healing and 'enlightenment'. Traditional stories about the origins of this powerful tonic weave together ancestral guidance, communication with the spirits of the plants, and the protection of visible and invisible guardians. Known by a variety of names including caapi, yajé, sainto daime and ayuhuasca, the drink is produced using the bark of the jaguba vine (Banisteriopsis caapi). The vine's three visible guardians, a grasshopper, the chicua bird and a snake, and invisible guardians must be appeased before harvesting (Luna, 1991). Despite these protective beliefs, traditional healers need to travel greater and greater distances to gather the bark from older, more potent vines. Increasing scarcity makes it often more practical to invest the time and effort in cultivation instead (Schultes, 1992). The vine of B. caapi can be readily grown from cuttings which contributes to the belief that each tendril and leaf is part of one continuous vine stretching back through time, described as an umbilical cord linking people to the past (Hugh-Jones, 1979).
The bark most commonly harvested from Banisteriopsis caapi (also collected from other forest vines or lianas in the same family) is peeled and boiled for several hours or pulverized in cold water to make a less concentrated batch. The resultant beverage is believed to be an effective treatment for many ailments, and is widely used in the Amazon. The type of hallucinogenic effects of the drink depends on many variables, including the time of day it was harvested, the preparation, the setting in which it is consumed and the addition of other plant species. The most frequent additives, used to both strengthen and prolong the experience, are leaves from 'oco-yajé' (Diplopterys cabrerana) and 'chacruna' (Psychotria viridis) (Schultes, 1992). They contain tryptamines which are usually inactive when taken orally, except when monoamine oxidase inhibitors are present. Not coincidentally the compound, harmine, found in B. caapi is this type of inhibitor. The colors and the entire experience induced by the drink appear to correlate distinctly to the quantity and combination of the various additives (Schultes and Hofmann, 1979). The recognition of such chemical fine tuning and its physiological results indicates a very sophisticated science. This leaves one wondering how traditional cultures arrived at such an unusual synergistic combination. As with the collection and production of curare, the preparation of the drink ayuhuasca has become highly ritualized. The adherence to ritual serves to both conserve the requisite plant species and standardize the end product, strictly replicating the original recipe generations after its first assemblage.
Despite thousands of years of human experience coupled with botanical variety, the intersections of diversity and human resourcefulness that produce new applications are unusual events. A vine in the family Bignoniaceae, found from Mexico to Argentina, is only known to be used by people in one place of its range. In a community in northern Colombia, several fishermen and their families were recently observed using a product from the vine to capture sand crabs. They manufacture a powder which they leave outside the crab's burrow. The crabs then eat it and are temporarily paralyzed, forced to wait until someone returns to collect them the following morning. The compound appears to be biodegradable as the crabs recover by the time they arrive at the local market and have been consumed with no apparent ill effects (Gentry, 1992). Perhaps this limited use for capturing crabs is an indication that it is not far from the time and place where it originated, but even from this proximity we are left with a single specific application as a record of a long and largely obscured past.
Was this article helpful?