EVOLUTION APPLIED to species is textbook stuff. Evolution applied to human cultures is not. Yet cultures do evolve and some of the clearest evidence comes from the transformation of old wives' tales into hospital practices.
Consider honey, a food substance with a long medicinal past. Ancient Egyptian medical papyri and Chinese medical texts recorded honey salves for burns, wounds, infections and sore throats. The ancient Aztecs used salted honey or a sugar concentrate from the maguey plant (a type of agave) for similar purposes and the Koran affirmed that in honey "is healing for mankind". More recently, Ameri-Indians of North America, African tribal healers, and Indonesians, have made medical use of the sweet, sticky stuff. Even captive chimpanzees and monkeys with access to concentrated sugar syrups spread these on their wounds - which suggests a common origin for this widespread human behaviour.
Useless, nonsensical practices? Not at all. In the early 1980s Dr Leon Herszage of Buenos Aires and Dr Richard Knutson of Greenville, Mississippi, reported that patients with surgical and traumatic wounds had significantly lower rates of chronic infection when treated with concentrated sugar pastes than with antiseptic/antibiotic regimens. Moreover, these pastes increased the rate of wound healing, decreased scarring and resulted in shorter, cheaper hospital stays. "Miracle cures" have subsequently been reported by British and African physicians treating chronic ulcerations with honey, and by Indian and Chinese doctors treating burns. Some French surgeons pack the heart cavity with sterilised sugar following open-heart surgery to cut post-operative infections.
The science behind the medical uses of sugar pastes and honey is simple. Concentrated sugar produces high osmotic pressure that destroys microbes by sucking the water out of them. This is how sugar preserves jams and jellies. Sugars also activate the immune system cells that begin healing and eliminate incipient infections. Some sugars interfere with the scarring process. And honeys contain antiseptics in the form of hydrogen peroxide and formic acid as well as numerous vitamins, minerals, and growth hormones that stimulate tissue growth.
How did ancient peoples discover these benefits? When it comes to medicine, experience often precedes explanation. Very probably, people preparing food sustained cuts and burns on their hands and noticed that if they subsequently handled honey or sugar pastes, their wounds felt better, healed faster, and developed fewer infections. Serendipity became folklore. Folklore became tradition. And finally, after thousands of years, tradition became clinically validated treatment. Both Knudtson and Herszage heard about honey treatments from nurses whose grandmothers advocated them.
For every evolutionary success of this sort, however, there have been myriad failures. Historical sources that list honey as a viable wound treatment also suggest chicken excrement, cow-dung, charcoal, ashes, and other agents. Nevertheless, these failures are part and parcel of medicine's vital evolutionary process. Human beings experiment with materials of all sorts to assess their medical value. By such means, the most useful agents, such as honey, emerge to compete successfully against less effective remedies, whether these be dung or antibiotics.
The recognition that medicine evolves has a practical benefit. Any natural substance or folk therapy that has survived for centuries has a high probability of yielding an effective clinical treatment. Thus the trial-and- error of folk medicine provides an important resource for modern research. Indeed, we can prime the pump of modern medical innovation by exploiting time- honoured medical practices of the past.
Robert and Michele Root-Bernstein are the authors of `Honey, Mud, Maggots and Other Medical Marvels' (Macmillan, pounds 12.99)
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