nomad (nōˈmădˌ) [key], one of a group of people without fixed habitation, especially pastoralists. (Some authorities prefer the terms "nonsedentary" or "migratory" rather than "nomadic" to describe mobile hunter-gatherers.) Wandering herders living in tents still occupy sections of Asia, and the hunting groups of the Far North, including the Eskimo, still predominate in much of the arctic and subarctic regions; parts of Africa and Australia are also peopled with nomadic groups. Although nomadism has been a way of life for many groups, it is on the decline. Besides the herders and the hunters and fishers, there are nomadic groups that move about in search of seasonal wild plants as food (such as the camass bulb formerly sought by the Native Americans of the Pacific Northwest and the wild rice gathered in the Great Lakes region). Peoples who move seasonally but have permanent homes for part of the year are said to be seminomadic; there have been seminomadic peoples of various types throughout history. The term semisedentary is applied to traditional populations who practice slash-and-burn agriculture in tropical forest clearings and are forced to move their villages periodically due to the soil exhaustion. Nomadic groups are generally organized in tribal units, and usually the adult males are closely knit into war bands in order to establish territorial rights over the area within which a group migrates. The incursions of nomads into settled civilizations marked the early history of ancient Egypt and Babylonia and reached their height with the great Mongol invasions of W Asia and Europe in the 13th, 14th, and early 15th cent., notably under Jenghiz Khan and Timur. Formerly efforts were made to generalize about nomads and find a common denominator among such diverse cultures as those of the North American Plains tribes, the Bedouin of Arabia, and the Romani (Gypsies), but these have largely been abandoned in favor of studying each culture as a unit. Even the idea that nomadism represents a transition from the Neolithic hunter to the sedentary farmer is not accepted as valid. There are instances of peoples who have abandoned farming and have become nomads, e.g., those Native Americans of the Great Plains who forsook their farms to hunt bison, after the horse had been introduced.