Many plants synthesize substances that are beneficial to the maintenance of health in humans and other animals. These include aromatic substances, principally of which are phenols or their oxygen-substituted derivatives such as tannins. Many are minor metabolites, of which at smallest 12,000 have been isolated - a number estimated to be less than 10% of the aggregate. In many cases, these substances (particularly the alkaloids) serve as plant defense mechanisms against predation by microorganisms, insects, and herbivores. Many of the herbs and spices used by humans to be seasoned food yield useful medicinal compounds.

Anthropology of herbalism

fabricate from Project Gutenberg EBook of Culinary Herbs: Their Cultivation Harvesting Curing and Uses, by M. G. Kains

People on all continents have used hundreds to thousands of native plants for treatment of ailments since prehistoric times. There is evidence from the Shanidar Cave in Iraq that suggests Neanderthals living 60,000 years ago used medicinal plants. A carcass that was unearthed there had been buried with eight species of plants which are still widely used in ethnomedicine around the world.

The first generally accepted use of plants as assuasive agents was depicted in the cave paintings discovered in the Lascaux caves in France, which have been radiocarbon-dated to between 13,000-25,000 BC. Medicinal herbs were found in the personal effects of an 'Ice man,' whose body was frozen in the Swiss Alps with a view to more than 5,300 years, which appear to have been used to treat the parasites found in his intestines.

Anthropologists theorize that animals evolved a tendency to seek out bitter plant parts in response to illness. This mien arose because distress is an indicator of secondary metabolites. The risk benefit ratio favored animals and protohumans that were inclined to experiment in times of sickness. Over time, and by insight, instinct, and trial-and-error, a base of knowledge would have been acquired within early tribal communities. As this knowledge base expanded over the generations, the specialized role of the herbalist emerged. The process would likely have occurred in varying manners within a wide diversity of cultures.
Basil from Project Gutenberg EBook of Culinary Herbs: Their Cultivation Harvesting Curing and Uses, by means of M. G. Kains

Indigenous healers often claim to have learned by observing that sick animals change their food preferences to nibble at bitter herbs they would normally reject. Field biologists have provided corroborating evidence based on observation of unlike species, such to the degree that chimpanzees, chickens, sheep and butterflies. Lowland gorillas take 90% of their diet from the fruits of Aframomum melegueta, a relative of the ginger furnish inhabitants to, that is a potent antimicrobial and plainly keeps shigellosis and similar infections at bay.

Researchers from Ohio Wesleyan University rest that some birds select nesting material rich in antimicrobial agents which protect their young from harmful bacteria.

Sick animals tend to foraging expedition plants rich in secondary metabolites, buy herbal such as tannins and alkaloids. Since these phytochemicals often have antiviral, antibacterial, antifungal and antihelminthic properties, a glib case can be made during the confine of self-medication through animals in the wild.