Living on the edge?

Claire Porter and Frank Marlowe of Harvard University have a concise paper in press in the Journal of Archaeological Science that tests the widely held idea that ethnographically documented forager groups live mainly in marginal environments. This is significant because some researchers have argued that, if known hunter-gatherers are (or were) restricted to such environments, they may not be adequate sources on which to base generalizations or models about prehistoric forager lifeways. They conclude that

“… foragers live in slightly (though not significantly) more marginal habitats than agriculturalists worldwide. However, this is mainly due to the large number of foragers who live far north of the equator in quite cold habitats where agriculture is not feasible… When we limit our analysis to the warm-climate sub-sample, foragers have a slightly higher habitat quality than agriculturalists, but there is again no significant difference.” (Porter and Marlowe 2006:4-7, in press).

Their method here is quite sound. They took a sample of 186 traditional societies (both foragers and agriculturalists writ large) from the Standard Cross-Cultural Sample, and plotted them geographically against the productivity of the region inhabited by each to derive an average value of habitat productivity. Like Binford (2001) and Kelly (1995), they use net primary productivity as the proxy measure for habitat productivity, except that unlike these authors, they use methods and data developed by programs at NASA to estimate it on a much finer-grained level. The downside to this is that NASA only had data from five years (2000-2004) available for Porter and Marlowe to use, which is one of the acknowledged limitations of their study.

It’s quite an ingenious way of looking at the problem, and it’s good to have an empirical demonstration that ethnographically documented foragers do not in fact live in more marginal environments than agriculturalists. In fact, in the warm zones where most of early human evolution took place (i.e., less than 40-45 degrees latitude and over 13 degrees effective temperature), foragers appear to inhabit slightly more productive habitats. As the authors argue, this may be in large part due to the fact that a good environment for foraging is not necessarily good for agriculture, be it intensive agriculture, pastoralism or horticulture. Another very good point to make.

It'll be interesting to see whether this approach to the issue of the ecology of hunter-gatherers gets taken further in the near future.

References:

Binford, L. R. 2001. Constructing Frames of Reference: An Analytical Method for Archaeological Theory Building Using Hunter-Gatherer and Environmental Data Sets. Berkeley, University of California Press.

Kelly, R. L. 1995. The Foraging Spectrum. Washington, DC, Smithsonian Institution Press.

Porter, C., and F. Marlowe. 2006. How marginal are forager habitats? Journal of Archaeological Science 33:in press.