The Domestication of the Rubber Tree: Economic and Sociological Implications
Schultes, Richard Evans, The American Journal of Economics and Sociology
The discovery of rubber is undoubtedly one of the greatest Indian contributions to modern civilisation.(1)
I have been a rubber tapper; I am a rubber tapper. I live in stagnant, muddy swamps in the loneliness of the forest with my crew of malarial men cutting the bark of trees that have white blood like that of the gods.(2)
ONE HUNDRED AND SEVENTEEN YEARS AGO, one of the most significant events in human history took place--the domestication of the rubber tree, Hevea brasiliensis. This achievement has had far-reaching economic, sociological and even humanitarian results.
In 1876, the British imported quite legally--contrary to widely disseminated tales--70,000 seeds of this rubber tree collected in the eastern part of the Brazilian Amazonia. They were transported to England and planted in greenhouses of the Royal Botanic Gardens, Kew. Some 2800 seeds germinated, and the eventually surviving young trees were sent to Ceylon and later to Singapore (2, 7, 12, 13, 14). Almost all of the extensive rubber plantations of the former British and Dutch colonies in Ceylon and southeast Asia and smaller plantations in sundry parts of Africa and elsewhere are based on this one species (2, 7, 8, 19).
HEVEA BRASILIENSIS, native to the Amazon region south of the Amazon River, belongs to the Spurge Family; there are nine other species of Hevea. Two other species, Hevea Benthamiana and Hevea guianensis, yield latex that gives a rubber somewhat inferior to that of Hevea brasiliensis (16). The latex of all the other seven species of Hevea are either hard to coagulate or provide a weak rubber of no use. Even some of these inferior latices might, however, one day be of value to the fast developing plastics industry as "fillers"--chemicals that may alter the physical properties of the new elastomers (15).
Botanists still are unsure of the function of latex in the life of the rubber trees, but it may serve a number of purposes. Some 37,000 species of plants in numerous families contain latex, a white or yellowish liquid. Only 7000 contain a substance called caoutchouc that will give usable rubber. It is difficult to realise that one species--Hevea brasiliensis--now supplies approximately 98% of the world's natural rubber, mostly from well-run plantations in Asia, Africa and Ceylon (8).
The latex of the commercial rubber tree is an emulsion of complex hydrocarbons which are long-chain molecules made up of hydrogen and carbon in units called isoprene. The latex of Hevea brasiliensis contains up to 6000 of these units; it is a polyisoprene (1, 2, 7, 9).
Most of the man-made substitutes--the elastomers popularly called synthetic rubber--have molecules with much fewer isoprene units. Some are better than natural rubber for certain purposes: e.g., when there is contact with petroleum products. But they are still inferior for tires which consume about 75% of the world's production of natural rubber (1, 8).
THE EARLY AMAZONIAN INDIANS had apparently very little use for rubber, according to brief reports by missionaries and explorers. In some tribes, apparently, small waterproof bags coated with rubber were made (6). A major interest in the rubber trees of several species was as a source of food. The seeds of Hevea are toxic, containing a cyanide, but when soaked in water and boiled, this poison is leached out, and the seed can be employed as a food (11).
Its use as a nutrient was first reported in 1775 by the French botanist Aublet in his book on the plants of French Guiana in which he described the genus and its first species: Hevea guianensis.
At about the same period, in 1770, a British chemist discovered that rubber could erase pencil marks--hence the English word "rubber" (2). When the Portuguese settled in the Amazon, they began to fashion a few articles of rubber; and in 1775, King Joseph of Portugal fostered the manufacture of shoes of rubber in Belem, at the mouth of the Amazon River. …