Rice is the desired staple food throughout Southeast Asia and may well have originated there. Rice can be grown on steep mountain slopes like maize or in deep pools of water (see Geertz 1963). Shifting cultivation in most of Southeast Asia supports a population density of only about 130 per square kilometer (Conklin 1957). This compares with population densities in some wetrice growing areas of Java of nearly 2,000 per square kilometer. The difference in overall densities is due to the fact that shifting cultivation requires that over 90 per cent of land be held in fallow at any one time. Thus while wetrice farmers far outnumber shifting cultivators throughout Southeast Asia, they are confined to a relatively small part of each nation’s territory. This can give rise to ethnic conflicts when pioneer farmers penetrate the highlands in search of new land.