This treatise describes fishing behaviour of people living at the village of Gwaimasi in the interior lowlands of Papua New Guinea. The concern is not with fishing as such but wdth the way in which social and ecological factors interact to influence behaviour. I argue that an adequate explanation for behaviour must incorporate both dimensions, and suggest a conceptual basis for achieving this. The study then illustrates how at least one aspect of social organization, the size of resource-sharing groups, could be incorporated within a frame of analysis - evolutionary ecology - that has typically focussed on the explanatory significance of ecological factors.
The primary thesis asserts that the probability of a particular pattern of behaviour being reproduced depends on both social and ecological factors. Variation in either domain can be expected to affect the kinds of behaviour observed, but the two domains do not affect behaviour in the same way. Ecological factors constrain production, the material outcome of action; social factors constrain consumption, the use that can be made of that outcome. The two domains are complementary, not contradictory, in their influence; in as much as production and consumption themselves are two facets of any action, ecology and society should be seen as mutually constitutive systems mediated by the actor.
Evolutionary ecologists have tended to analyse constraints on production, particularly extrinsic constraints on production, in explaining behavioural variability. While constraints on consumption are not ignored, they are usually discussed only in terms of the intrinsic requirements of the actor. I argue that consumption, like production, is subject to extrinsic constraints; the use that an individual can make of a particular outcome of action may depend on the actions of others. In particular, where a resource has declining marginal value, the amount that is likely to be received from others will limit the amount that an individual can usefully procure; as a corollary, the expectation of having to distribute produce among others will increase the amount that can be usefully procured. In each case, the effect will depend on the size of the resourcesharijig group.
These arguments are illustrated by analyses of the fishing behaviour of people at Gwaimasi over a period of 57 weeks, Eariy chapters set the scene for those analyses, introduce the actors and position fishing within their broader subsistence arrangements. The community was small and isolated, the people hunter-horticulturalists using about 50km2 for subsistence. Skulls of neariy all fish caught within that area during the survey were purchased, and details recorded of fisher, technique, location and context of capture. In addition, records were kept of where individuals were based within the local area each day. Analyses of these data indicate that whether people chose to fish, as well as where and how they fished, depended on both the outcome that could be expected from the decision and the use that could be made of the outcome. Availability and accessibility of fish placed extrinsic constraints on production and, allowing for the relative time required to reach different fishing locations, people clearly preferred those streams and techniques that produced the largest hauls. But individual fishers differed in their intrinsic abilities to procure fish and in the use that they could make of fish. Differences in access to equipment, experience or information affected the viability and efficiency of fishing techniques. Differences in nutritional and social requirements affected the need for fish. Thus, men and women, people at different life-history stages, and those affiliated with different clan groups displayed rather different fishing behaviour, with the contingencies of heredity and experience adding a further layer of variation crosscutting these structural categories. Most importantly, the size of the resource-sharing group at the village, which changed as residents moved about and beyond the local subsistence zone, placed extrinsic constraints on consumption of fish. As the size of the group changed, and with it the amount of fish which could usefully be produced, fishing behaviour changed markedly.
The study demonstrates cleariy that social factors, as well as ecological factors, can influence patterns of production; both domains must be considered in any adequate explanation of behaviour. It is also clear that the emphasis which evolutionary ecology has placed on production, and on factors affecting the material outcome of production as the basis of explanation, is not inherent in its methodology. I have demonstrated that that methodology is entirely appropriate to the study of social constraints on behaviour.