with the beginning of agriculture and animal husbandry, human societies changed radically, with a breakdown of boundaries between erstwhile endogamous tribal groups. due to this, there may occurs amalgamation of the many streams of the knowledge and there may have developed a variety of specialised groups of people concerned with management of particular stocks of knowledge, such as that dealing with fashioning of tools or use of herbal medicines. merging of different knowledge streams and their use has led to rapid expansion of the total flow as the hunter-gatherers societies transformed into agrarian one (gadgil 2001b). for thousands of years, aboriginal peoples around the world have used knowledge of their local environment to sustain themselves and to maintain their cultural identity. only in the past decade, however, has this knowledge been recognised by the western scientific community as a valuable source of ecological information.