774 nomadic and pastoral societies: The Americas herders who practiced their craft in the grasslands of eastern and southern Africa worked closely with neighbors who specialized in farming, hunting, fishing, or foraging These specializations often exploited ecological niches, such as the different elevations of the hills and mountains of the Great Rift Valley, so it was important for communities to work together to ensure food security in the face of the specific threats of each environment The Americas by David H Vallilee The term nomadism derives from the Greek word nomas, meaning “feed” or “pasture.” Generally, it has been defined as a circumstance in which people have no permanent home and wander in search of food and pasture It also applies to peoples whose subsistence is largely based on hunting migrating mammals, with the result that the location of their temporary shelter is contingent upon herd movements and a need to avoid excessive hunting in one place In many regions movement is based on seasonal changes in which some areas are abundant in animals and plants in the warmer months and others more abundant in colder months Nomadic pastoralism is based upon herding domesticated animals and often requires moving animals to the best pastures Pastures in arid regions may not be useful outside of the rainy season, while pastures in mountainous and colder regions may not be accessible in winter These conditions necessitate moving livestock between different regions seasonally Nomadic pastoralists can move to a wide variety of places according to the availability of pastureland, whereas transhumant pastoralists move between fixed locations each season While much of the population of the Americas during the medieval period lived in permanent settlements, people in some regions still practiced nomadic ways of life Between 500 and 1500 the North American Arctic region from Alaska to Greenland was dominated by two cultures, the Dorset and the Thule The Dorset culture dominated the northern area of the present-day Northwest Territories of Canada and western Greenland from about 500 to 1000 The Dorset were a seminomadic people whose primary economic activity was hunting They occupied autumn camps for hunting seal and walrus; late-winter and spring camps for hunting caribou, musk oxen, and polar bears on the polar edge; and summer camps for hunting, fishing, and gathering plant foods Late in their culture they built longhouses for ceremonies during snow-free parts of the year More than 90 percent of the Dorset diet consisted of game and sea animals augmented by plant and sea foods, such as clams, mussels, berries, leaves, lichens, and seaweed They carved harpoons for hunting sea mammals and spearheads for hunting fish The Dorset had considerable knowledge of animal behavior and precisely timed their hunting activity during the year They intercepted migrating harp seal in narrow channels, concentrated on hunting nesting birds rather than on the more elusive migratory fowl, and specialized in the selective hunting of animals of particular ages when these groups were most abundant Dorset carving achieved a high level of naturalism in miniature, such as tiny ivory carvings of humans holding infants, animals and human-bear composite figures, carved figures of wood and stone of humans wearing parkas, and ivory harpoon heads with animal effigies Around 100 the Thule culture emerged in northern Alaska After spreading across Alaska they began a period of great expansion from about 1000 to 1300, extending eastward across the entire North American Arctic zone and into western Greenland, overtaking most of the Dorset territory The Thule migrated between two types of settlements, winter base camps and hunting and fishing camps Their subsistence was based on hunting large game animals (caribou and musk oxen) and sea mammals (seal, walrus, and whale), net fishing at sea, and freshwater fishing from rivers and streams Agricultural products were not present in their diet The Thule economic pattern, facilitated by long-distance kayak and dogsled travel, appears to have been focused upon particular hunting endeavors and opportunities to exploit a greater variety of food resources They also achieved cooperative hunting activities, such as whaling crews The Native Americans of the Great Plains encountered by Euro-Americans during the period of exploration, expansion, and trade (about 1550–1900) became emblematic of nomadic, indigenous North America, well known for their portable tepee shelters, their military achievements, and their buffalohunting skills In the centuries prior to the introduction of guns and horses to the region, the nomadic inhabitants of the Great Plains hunted bison on foot with bow and arrow Often their aim was to procure large numbers of these bountiful animals through communal hunting activities, such as bison jumps and bison corrals Bison jump sites are characterized by a high bluff over which the animals were stampeded so that large numbers of them would be killed and crippled by their fall and others would be killed by hunters waiting at the base of the bluff Bison corrals were bowl-shaped rock formations where large numbers of bison could be driven into the enclosed area, trapped, and slaughtered quickly One of the most prolific bison jumps was the Head-Smashed-In site in southern Alberta, Canada, with evidence of continuous use between 3600 b.c.e and 1300 c.e The Wardell Bison Corral in western Wyoming, which included a large butchering, process-