Wobst’s population model

11 minute read


Wobst, H. Martin. 1974. Boundary conditions for Paleolithic social systems: a simulation approach. American Antiquity 39(2):147-178. JSTOR

To me, this paper is a landmark. The reason why is that it is a serious attempt to make something out of nearly nothing. The nearly nothing is precisely what we know about the social structure of hunter-gatherers. Wobst has only the barest of basics to begin with: exogamous bands of around 25 individuals, organized into larger groups (here called maximum bands) that are territorial and endogamous. There is little of substance to add here, beyond the size of the maximal band and some idea of its geographic extent, but in a sense these details are reserved for cross-checking the end result of the simulation (although not literally so). The something that Wobst constructs is not a general model for Paleolithic social structure–this model falls directly from his assumptions, and its validity is no greater or less than that of the assumptions themselves. The real accomplishment of the study is the derivation of several other consequences of the assumptions that are not in the least bit obvious corollaries.

Thus, it was surprising to me in a quick check of Google Scholar that the paper does not have more of a following. This is an imperfect comparison, since it focuses only on publications available to the service (i.e. recent and web-accessible), but I think it reflects a general perception about the paper. Most of the people I know are well aware of the paper and its arguments, but few see any practical applicability. In this context, Wobst’s apparent concern for contextualization is well-founded. It is all well and good to formulate a general model of what Paleolithic social structure may have been like, but this in effect is a global hypothesis for which none but extremely local tests are really possible.

So who cites the paper? Fundamentally, if you need a model of Paleolithic social structure, this is the study to start with. The fact is that beyond Wobst’s references there is very little to go on in terms of concrete ethnographic comparisons. There are critiques of the numerical values taken as Wobst’s assumptions, but there is certainly nothing much better to work with. And the logical arguments behind some of the derivations may be quibbled with, but there is no fundamental flaw in them that would require taking up an alternative logic. A global model of population structure is a basic prerequisite for genetic studies of ancient demography, for hypotheses about the ecological relationships of ancient groups, and for studies of the migration and interaction of ancient peoples. They underlie much of evolutionary psychology, with its focus on the social and cultural interactions that may have served as global standards (or rough averages) during human evolution.

Even the preamble of the paper is interesting–it is as concrete a demonstration as one might find for the reality of a “Michigan” school of anthropology. Here we can see Wobst arguing for archaeology as a mode of investigating “cultural systems” and as a key to the development of “general cultural theory” (148). It resonates for the biological anthropologist because at the very same time paleoanthropologists were discussing the power of culture as an active element in shaping human evolution, including the assertion that culture was the “adaptive niche” to which humans were more or less adapted. Ideas like these were by no means limited to Michigan at the time, but in a department with the legacy of Leslie White they had a status as serious statements of cultural theory that they have never again enjoyed. These attempts by archaeologists and biological anthropologists were not the mainstream of cultural theory, which was already in the grips of Derrida, or at least Clifford Geertz. Indeed it is somewhat ironic to read Wobst discussing how Paleolithic studies had moved toward a steadily closer alliance with social studies over the preceding century, when at that very moment the social sciences were moving toward a rejection of most of the ideas Wobst was embracing.

Nevertheless, this preamble does not really serve as a foundation for the argument to follow; rather, it serves to contextualize it. The underlying concern that Wobst takes time to address is whether general theoretical statements about the behavior of past groups may be tested using the shovel-in-the-ground data from real archaeological sites. His position here is that the data increasingly was being used for testing hypotheses of cultural or social content, and so there is no logical barrier to further work along these lines. Wobst also reminds us that theory in archaeology precedes the recovery of better data–instead of the other way around–because everyone would remain satisfied with the previous level of data collection if there were no logical reasons to work more intensively (150).

Minimum and maximum bands

Wobst takes these terms from Julian Steward (1969). They are often treated as equivalent to Joseph Birdsell’s categories of band and “tribe.” Moreso than for most human social groups, and more akin to social groups in other mammal species, these groups have reality only to the extent that structured behavior reinforces them. In hunter-gatherer groups, the flexibility of the social units is such that neither type of band is static over its lifespan, or even over the lifespan of individual humans. These groups are dynamic in membership, in territory, and in their interactions with other groups.

Significantly, both kinds of bands delineate social networks that are larger than a nuclear family or comparable kin group. This means that the forces that maintain these groups formally occur at a different level from the interactions typical of close kin. For the minimal band, the individuals may be related by more distant kinship or affinal ties, and Wobst notes the kinds of factors that cause minimal bands to persist including, “cultural practises of cooperation among its members, division of labor according to age and sex, and mutual food-sharing” (152). The size of the minimal band is contrained by ecological facts: larger groups are desirable to reduce risk (predation risk, risk of hunting failure, risk of incursion by other groups) while smaller groups are desirable to minimize competition for food and other resources.

Wobst introduces the maximum band as:

a marriage network which guarantees the biological survival of its members, since the members of a minimum band have to rely on a larger number of persons than their own membership in order to provide a member with a mate upon reaching maturity (152).

It is the exchange of mates among minimum bands that enables the social integration of the maximum band, to the extent it exists. This includes details like shared cultural rules and language, as well as direct negotiations among members of different minimum bands for access to resources like exotic materials and mates themselves. This integration occurs along religious and ideological lines that differ among different hunter-gatherer cultures.

Given these constraints on maximum bands, Wobst predicts two boundary conditions. The minimal equilibrium size is the size of a maximum band that “will consistently guarantee the presence of a suitable mate for a group member auon reaching maturity” (154). This size depends on the marriage rules of the society–for example, prohibitions upon mating with distantly related kin will decrease the number of suitable mates for an individual and thus require a larger minimal equilibrium size to maintain the same mate access. The second boundary condition is the maximal equilibrium size which is “the maximal number of people which can be consistently integrated by the cultural mechanisms of a given cultural system and which is consistently required for the successful operation of such a cultural system” (154). This latter condition is fairly nondeterminate, but the former is a potentially important constraint: if the “cultural system” cannot integrate a given number of people successfully, then some number of them will undoubtedly fission to create a new group.

This is the stream of thought that currently underlies Robin Dunbar’s work on social group size in primates; namely that the maintenance of social groups of a given size requires an investment of time on the part of each individual, and without the innovation of new methods of social control this investment ultimately must limit social group size. Whether human groups face this barrier at around the maximal equilibrium size of hunter-gatherer societies is undetermined, but this is the speculation of Dunbar and others. It is to some extent an unfounded speculation because it rests on the assumption that in the absence of such a constraint on group size, group sizes would be larger than they are. This assumption is unfounded, since it implies that larger groups are better in some way that has not been demonstrated. For example, we might as easily believe that the constraints on group size were not due to time constraints on interaction but instead due to ecological reasons. Another option is that group size is influenced by a balance between within-group competition (for political or economic dominance) and between-group competition (for resources or territory), in just the same way that minimum band size is generally thought to be determined. Under that scenario, there is no special social dynamic occurring within the maximum band, and the emergent characteristics at the maximum band level, such as language dialect, religious ideology, and oral history, are themselves derived from the quasi-historical reality of the group rather than any active role of such groups in normalizing human cultural development. At that, Wobst himself says “It is doubtful, however, whether the maximal equilibrium size has any bearing on the cultural system of Pleistocene hunters and gatherers” (154).

Wobst argues for the primacy of the minimal equilibrium size for Paleolithic groups:

What's up with the hexagons?

The most idiosyncratic of Wobst’s assumptions is the formulation of a hexagonal abstraction for the geographic arrangement of groups. The hexagonal model is not problematic: it represents the most efficient packing arrangement for equal-sized units upon a two-dimensional surface. For this, the assumption of hexagons is not strictly necessary except to eliminate the “unaccounted voids” (153) that circular territories leave between neighboring groups. To support the idea of a hexagonal arrangement Wobst provides a brief survey of the number of territorial boundaries for bands of different ethnographic hunter-gatherers, finding an average between 5 and 6–thereby supporting the 6-plex arrangment of hexagons in his model. But this may be a fairly general characteristic that reflects any spatial network, regardless of territory shape: consider that there are 11 contiguous U.S. states west of the Mississippi River that lack an ocean shore or national border, and these states have an average of 5.8 neighbors, despite the fact that most of them obviously approximate rectangles in shape.

Less obvious assumptions

Here are several of the less obvious assumptions used by Wobst but not included in the master list of assumptions. These are foci of interest because they illustrate much about the intuitive model of small-scale societies typically deployed by paleoanthropologists.

  • "[E]cological restraints on population agglomerations of hunters and gatherers" (154).
  • "[T]he lack of intraband specialization except by sex and age" (154).
  • "[I]f a local group leaves the niches it is accustomed to exploit, its chances of success in hunting and gathering decline while its chances of failure due to unpredictable events increase. Thus, long-distance moves would tend to lower the population density and introduce an element of instability into an interregional social network" (153). I wonder if this assumption can be restated as a general rule applying to any information-dependent foraging society. Clearly, moving causes risk and the net effect of risk, averaged over many groups, must be to decrease the population size. We may ask whether the risk of not moving balances the risk of moving at some point, and thereby drive a global model of response to local environmental deterioration, as faced by the Neandertals, perhaps. On the other hand, humans probably never had the choice of large-scale dispersal, as argued by Wobst in the next few paragraphs, because most territories suitable to human occupation were never empty after their initial habitation.

One problem with the paper is its assumption that “Paleolithic” equals band-sized social organization. At some point in the past, it is probably possible to assert that large social units were simply not possible. But this time certainly did not encompass all of the Paleolithic, since Upper Paleolithic peoples to a greater or lesser extent were capable of agglomerating into relatively large village-sized social units for long periods of time, possibly using specialized technological and cultural solutions based on local food and resource abundances such as salmon runs or animal migration choke-points. Large social groups would have enabled social complexity beyond that contemplated here, without requiring extractive methods outside the scope of “hunting and gathering.” They may well have been limited to regional importance or importance over limited timescales, in the end constraining their possibilities for growth and increasing sophistication, but nevertheless imply very different things for social controls and “boundary conditions” than envisioned in the band-level model.

This raises the question of whether there was any time that the band-level organization model had real adaptive importance for humans. Even if the majority of humans around the world were organized in this maximum band-minimum band social structure, nevertheless we might imagine that selection was most powerful not in this stable context but in the unstable social contexts accompanying local or temporally constrained large populations. It was in these places were rapid population growth, and subsequent dispersal to more marginal areas, was possible. It was therefore in such small, high-density populations that we might expect to find the most active adaptation toward the mental and social characteristics of recent human societies.