their herds to southern villages with a more temporary character. They then move inland, where they stay in tent camps. In Chad, the sturdy villages are called hillé, the less sturdy villages are called dankhout and the tents ferik. David Christian's account David Christian made the following observations about pastoralism. The agriculturist lives from domesticated plants and the pastoralist lives from domesticated animals. Since animals are higher on the food chain, pastoralism supports a thinner population than agriculture. Pastoralism predominates where low rainfall makes farming impractical. Full pastoralism required the Secondary products revolution when animals began to be used for wool, milk, riding and traction as well as meat. Where grass is poor herds must be moved, which leads to nomadism. Some peoples are fully nomadic while others live in sheltered winter camps and lead their herds into the steppe in summer. Some nomads travel long distances, usually north in summer and south in winter. Near mountains, herds are led uphill in summer and downhill in winter (transhumance). Pastoralists often trade with or raid their agrarian neighbors. Christian distinguished ‘Inner Eurasia’, which was pastoral with a few hunter-gatherers in the far north, from ‘Outer Eurasia’, a crescent of agrarian civilizations from Europe through India to China. High civilization is based on agriculture where tax-paying peasants support landed aristocrats, kings, cities, literacy and scholars. Pastoral societies are less developed and as a result, according to Christian, more egalitarian. One tribe would often dominate its neighbors, but these ‘empires’ usually broke up after a hundred years or so. The heartland of pastoralism is the Eurasian steppe. In the center of Eurasia pastoralism extended south to Iran and surrounded agrarian oasis cities. When pastoral and agrarian societies went to war, horse-borne mobility counterbalanced greater numbers. Attempts by agrarian civilizations to conquer the steppe usually failed until the last few centuries. Pastoralists frequently raided and sometimes collected regular tribute from their farming neighbors. Especially in north China and Iran, they would sometimes conquer agricultural societies, but these dynasties were usually short-lived and broke up when the nomads became ‘civilized’ and lost their warlike virtues. Around the world Nomadic pastoralism was historically widespread throughout less fertile regions of Earth. It is found in areas of low rainfall such as the Arabian Peninsula inhabited by Bedouins, as well as Northeast Africa inhabited, among other ethnic groups, by Somalis (where camel, cattle, sheep and goat nomadic pastoralism