Before we can investigate the role of demographic processes in subsistence farming, we need to explore some of the basic features of such farming. As argued in the previous chapter, we can understand the impact of demography only if we can link it to specific mechanisms operating in such farming regimes – which means we need to identify what the relevant mechanisms are from real-world field observations. Most of the empirical evidence concerning subsistence farmers and their farms comes from in-depth studies of living communities in the farther reaches of the rural developing world, studies conducted by anthropologists, geographers, economists, ethnobotanists, ecologists, agricultural scientists and others. Most of this field research has post-dated 1950, which means that many of these purportedly traditional farming operations had already been “contaminated” to some degree by the modern world – by the penetration of markets, the commercialization of food, the rise of wage labor, the exhortations of agricultural extension officers. In this book, I have drawn as far as possible on studies in which the contamination is limited and to some extent “correctable.” Often this has required examining older literature – scarcely a hardship since the older material is often of very high quality. The studies I draw upon are extremely diverse, but the majority are either cross-sectional or of short duration (a few years at most) – a fact that often limits our ability to observe and understand the inherently dynamic nature of farming. Sometimes archaeological and historical reconstructions can provide greater time depth, but they are unable to recover many of the fine details of farming behavior. Even restricting attention to studies of living farmers (living, that is, at the time of study), we find little standardization of research methods, not surprising given the long time span over which these studies were done and the diverse professional backgrounds of the authors involved. The literature is huge, and I do not attempt to review it all; in this chapter I emphasize topics that are important for later chapters. In the appendix to this book, however, there is a bibliographical essay that provides pointers to the larger literature.