Introduction

When speaking of foragers and collectors we are referring to people living off the land by hunting wild animals, gathering wild plants, and fishing, people who are not exercising any control over the reproduction of exploited animals and plants. This remains true even in the present times when some contemporary hunters and gatherers, like the Ache of Paraguay who cut down trees and visit them later in the season to collect worms, or the Nukak of Colombia whose movements are organized depending on the wild orchards resulting from the seeds of the fruits that remained on the ground of abandoned camps.

Today, only a few scattered groups pursue a hunting and gathering way of life, and often they do

So either by engaging in mutualistic associations with agriculturalists or pastoralists, or by practicing some horticulture or tending of animals. Often these economic arrangements are very close to slavery. Moreover, these hunters and gatherers are spatially restricted to economically and geographically marginal places in different parts of the world. This variety of situations prompted a debate around the definition of hunters and gatherers, which was centered in the forager populations of Southern Africa, the so-called Bushmen. At stake was their status as pure hunters and gatherers or as the result of contemporary pressing forces. Whatever the merits of both positions - and there is indeed value on both fronts - one basic result of the debate is a richer and more complex image of the many ways in which foragers can organize themselves, ranging from economically and socially complex to simple and highly mobile groups. This is important because foraging was in the distant past the basic way of life around the world, and as it is often emphasized, that was the case for at least 99% of human history.

Another conclusion derived from this debate is that modern hunters and gatherers are not very good analogs for the interpretation of the archaeological past. This observation puts a limit on the value of ethno-archaeological results, which many times were used to produce direct analogies for the interpretation of the archaeological record. Then, one result of the debate was to confirm that methodology is the field where ethno-archaeology can best contribute to the advancement of our interpretative skills as archaeologists. For example, ethno-archaeological studies can help us to decide which analytical methods are more suited for the description and explanation of the subsistence, social organization, or mobility of past foragers. Since the contemporary world is of limited value for the direct understanding of past societies, it follows that the results of archaeological research should be intensively used. Then, patterns derived from archaeological studies of hunter and gatherer adaptations should have a crucial role in shaping our image of past foragers. However, ethnographic and ethno-archaeological studies also produced results that impacted the practice and understanding of archaeology beyond methodology. In sum, it can be inferred that the results of both the contemporary and the archaeological research enterprises can be usefully combined in a single explanatory framework in order to learn about the past.

The study of the interactions between foragers and their environments has always been a key research area. The extent of these relations was captured by the forager-collector continuum, as defined by Lewis R. Binford in a famous paper published in 1980. This continuum emphasizes the differences between very mobile communities with low numbers of people and whose subsistence exhibits little planning - the Foragers - and people who enjoy a limited degree of sedentarism, spending at least several weeks or months at a central hub engaging in a more sophisticated system of food exploitation and conservation, and aggregate in higher numbers - the Collectors. Moreover, a worldwide search conducted by Binford identified a latitudinal pattern in the distribution of hunter and gatherer societies. He found that those societies located closer to the equator usually had a forager orientation, while collector societies were numerically more at higher latitudes toward the Poles. These patterns are derived from the basic relationship that exists in nature between latitude and the distribution of resources. Some organizational properties of the bands exploiting those-resources varied accordingly with seasonal and spatial availability.

The already-mentioned Ache of Paraguay constitute a good example of what Binford called a forager society. Back in the 1960s, before they were concentrated in missions, the Ache moved around a lot, at times more than 60 times a year. High mobility produced many small camps that were used by a few people, who basically hunted medium-sized mammals and gathered fruits for the day. The camps were formed by simple huts which were made of palm leaves. They offered protection against the rain and were constructed in a few minutes. Ache bands aggregated only rarely, and only for a short time. On the other hand, the classic example of collectors is the

Nunamiut of Alaska, with whom Binford worked for years. They exploited several different resources, especially migratory caribou (Rangifer tarandus), other smaller mammals, fish, and birds and from a central location. Many of these resources were available at different times of the year and at widely separated places. Logistical expeditions, usually implying several days outside of the base camp, needed to be organized in order to exploit this variety of resources. Techniques of meat conservation were used to preserve meat for the winter. The Nunamiut spent most of the year in aggregation camps, where they occupied well-constructed wood structures.

Being foragers and collectors are not the only ways in which hunters and gatherers can organize themselves, but it is a practical way of understanding some of the basic ties of small-scale human aggregations with the environment in which they made a living. In fact the forager-collector continuum can be partially assimilated to the distinction made by James Wood-burn between hunters and gatherers with immediate and delayed-return economies. The archaeological applications of this concept clearly show that it is more a framework around which research can be organized, than a fixed formula within which cases can be accomodated. A fertile ground for archaeological research, which is at least partially derived from the forager-collector continuum, is the study of lithic instruments in terms of curated versus expedient technologies. In turn, studies of the design of instruments and the provenience of the rocks selected to construct them constitute refinements that help to tackle the study of hunters and gatherers around the world. Several expectations specifically derived from the forager or collector models for faunal remains were also useful for the development of new quantitative techniques of archaeofaunal analysis. In fact, many of these techniques were generated or discussed in ethno-archaeological settings.