Use of herbal medicines may have arisen by accident

[Guest guest]

Use of herbal medicines may have arisen by accident. Nature News

Service 18 June 2004

MICHAEL HOPKIN

From the 41st Animal Behavior Society meeting, Oaxaca, Mexico

Devotees of herbal supplements claim a bewildering array of health

benefits from the plant-based pills. But how were these effects

discovered? A new theory suggests how people might have begun eating

certain plants without knowing about their medicinal effects.

" I'm intrigued by the level of fascination herbal medicines have for our

current society, " says Ben Hart, a veterinarian at the University of

California, , who developed the theory. Many people swear by the

supplements' ability to treat ailments ranging from backache to

depresson.

Animals are also known to practise herbal medicine, Hart told the annual

meeting of the Animal Behavior Society in Oaxaca, Mexico. Chimpanzees,

for instance, chew on the bitter pith of the plant Verouta, not normally

a part of their diet, to ease pain.

The animals cannot know exactly what they are doing, Hart argues. With

instances of illness few and far between, and plants that vary in speed

and effectiveness, it would be impossible for animals to link cause and

effect.

his means that the use of herbs as medicines may have been encouraged by

natural selection rather than conscious learning, Hart suggests. Animals

that eat pain-relieving

plants, for instance, would be better able to forage or look after young

during a bout of illness.

But how could this habit arise unconsciously, Hart wondered. He searched

the records of medical trials of 25 herbal supplements that have proved

to be effective in humans.

Some 78% of them came from plants that have a bitter or astringent

taste.

Animals that happened, by chance, to develop a penchant for bitter

plants when feeling off-colour would therefore be less vulnerable to

sickness, Hart says. And if they passed that preference on to their

offspring, the habit would become a tradition, or an evolved trait.

The idea that certain herbs are used simply because they taste bitter

could also help to explain the many spurious claims made by advocates of

herbal supplements, Hart

suggests. " It's one way of explaining the persistence of ineffective

medicines in modern use, " he told the meeting.

Hart admits that his idea is untested. And he concedes that humans do

now have a conscious appreciation of supplements' effects, and can pass

that knowledge on to

others. " Humans can say 'when I got sick I took this or that', " he says.

" But it's pretty hard to imagine that happening in animals. "