Almost every aspect of Mongolian society has been shaped by pastoral nomadism, an ecological adaptation that makes it possible to support more people in the Mongolian environment than would be true under any other mode of subsistence. Pastoralism is a complex and sophisticated adaptation to environments marked by extreme variability in temperature and precipitation, on time scales ranging from days to decades. Mongolia's precipitation is not only low on the average; it varies widely and unpredictably from year to year and from place to place. The dates of first and last frosts, and hence the length of the growing season, also vary widely. Such general conditions favor grasses rather than trees, and they produce prairies rather than forests. Grain can be grown under such conditions, but not every year. Any population attempting to support itself by cereal agriculture could expect to lose its entire crop once every ten years, or every seven years, or every other year, depending on the localities they were farming. Because ecological systems adapt to extreme limiting conditions rather than to the mean of variation, agriculture is not adaptive to Mongolian circumstances.
Pastoralism, however, permits societies to exploit the variable and patchy resources of the steppe. The key to pastoralism is mobility, which permits temporary exploitation of resources that are not sufficient to sustain a human and herbivore population for an entire year. Pastoralism may be combined with agriculture if a stable resource base, such as an oasis, permits, or agriculture may serve, as in central Mongolia, only to supplement herding and may be practiced only to the extent that labor is available.
A host of features of nomadic life reflect the demands and costs of mobility and of dependence on herds of animals to convert the energy stored in grasses to the milk and meat that feed the human population. Such societies commonly develop a conscious and explicit nomadic ethos, which values mobility and the ability to cope with problems by moving away from threats or toward resources and which disparages permanent settlement, cultivation of the earth, and accumulation of objects.
Societies based on pastoral nomadism do not exist in isolation, and nomads commonly live in symbiotic relationships with settled agriculturalists, exchanging animal products for grain, textiles, and manufactured goods. Both the nomads and the agriculturalists can, if necessary, survive without the goods provided by the other, but under most circumstances both benefit from exchange. Mongols typically dressed in sheepskin tunics covered with Chinese silk; drank tea from China; consumed a certain amount of millet, barley, and wheat flour; and used cooking pots and steel tools produced by non-nomadic smiths, some of whom were Mongols and some Turkic speakers or Chinese. However, the scattered nature of the population and the necessity of moving trade goods long distances by camel caravan limited the quantity of bulky goods available to nomads.
Data as of June 1989