At Gome National Park in Tanzania, primatologists found that one particular species of leaf kept appearing undigested in chimpanzee dung. They found that every few days the chimps would vary from their usual pattern of eating wild fruit. Instead, they would walk for twenty minutes or longer to the site where a species of Aspilia was growing. They would repeatedlyplace their lips over an Aspilia leaf and hold it in their mouths. Chimps were seen to pluck a leaf, place it in their mouths, roll it around for a few moments, then swallow it whole. In this way so many as thirty small leaves might be eaten.
Biochemist Eloy Rodriguez of the University of California, Irvine, isolated the active princile from the Aspilia--a reddish oil now named thiarubrine-A. Working with the same substance, Neil Towers of the University of British Columbia found that this compound can kill common bacteria in concentrations of less than one part per million. Herbarium records studied by Rodriguez and Towers (1985) showed that African peoples used the same leaves to treat wounds and stomachaches. Of the four species of Aspilia native to Africa the indigenous peoples used only three; the same three species were the ones utilized by the chimpanzees.
These findings show clearly the way in which a beneficial plant, once discovered by an animal or a person, can be included in the diet and thus confer an adaptive advantage. The animal or person is no longer threatened by certain factors in the environment, such as diseases that may have previously set constraints on the life span of individuals or perhaps upon the growth of the population as a whole. This type of adaptive advantage is easily understood. Less easy to understand is the way in which plant hallucinogens might have provided similar yet different adaptive advantages. These compounds do not catalyze the immune system into higher states of activity, although this may be a secondary effect. Rather, they catalyze consciousness, that peculiar, self-reflecting ability that has reached its greatest apparent expression in human beings. One can hardly doubt that consciousness, like the ability to resist disease, confers an immense adaptive advantage on any individual who possesses it.
