The Redención del Campesino Valley Archaeological Survey

Dempster-Shafer Theory and Site Prediction Modeling

In a previous study aimed to determine the whereabouts of an un-located polity of the Upper Usumacinta region: Sak Tzi’i’ I, applied Dempster-Shafer logic to identify all the locations in the region where the likelihood of the presence of a major center would be higher (Anaya 2001b). The parameters used to evaluate this probability were proximity to main routes of communication and distance from other major centers.

Dempster-Shafer theory belongs to a relatively recent development of Decision Support Systems in GIS known as Uncertainty Management. This differs from the more traditional approaches in GIS where the models and databases are implied to be "perfect" thus leading us to take "hard" decisions. Dempster-Shafer theory instead recognizes as a working principle the concept of ignorance. To obtain a measure of the likelihood that an archaeological site will be found at a specific location, Dempster-Shafer logic creates a frame of discernment. This is intended to exhaust all possible combinations of the variables involved. In this manner it takes into account ignorance by setting the variables in a frame of discernment that tests a "site hypothesis", a "non-site hypothesis", and the combination of both, "site-non-site" (Clark Labs 1997:9.23).

Thus the strength of this approach lies not only in recognizing these uncertainties, but also in providing us with the means to deal with them by the creation of three complementary measures of likelihood: Belief, Plausibility, and Belief Interval. Belief constitutes the degree to which evidence provides support for a given hypothesis (in this case the presence of an archaeological site). Plausibility constitutes the measure to which the evidence does not refute that hypothesis. And finally, the Belief Interval constitutes the difference between belief and plausibility, and it acts as a measure of uncertainty, thus allowing us to assess the degree of ignorance (Clark Labs 1997:9.32, 9.37).

In this case I want to emphasize on the results obtained in the Belief Interval image (Figure 3), because the most important aspects of this is the identification of those areas where further research is warranted. Notice that the highest values in this image concentrate on those areas where communication routes converge, and/or where critical points in terms of movement are present (e.g. rapids).

The results of my previous research prompted me to apply the same approach for the identification of those areas where strategically located subsidiary sites could be present. By comparing the various landscape attributes that other subsidiary sites such as El Cayo, La Pasadita, La Mar, Panhalé, Cascada Lacanha, Chinikiha and San José had (Anaya 2001b), the following variables were selected:

1. Distance from channels of communication (rivers, landing beaches, portages, mountain passes) from 0-1000 meters.

2. Located on gentle slopes: <= 5º.

3. Distance from steep slopes (defensible location) from 0-500 m.

4. Distance from Primary centers =< 5000 m.

5. Distance from other secondary centers =<3000 m.

The results from the Dempster-Shafer analysis were reclassified to select only the high probability values and are presented in Figure 4, overlaid on the topographic map of the valley.

As mentioned at the outset the inscription of the Álvaro Obregón wooden box provided substantial support towards the assumption of the presence in the valley of an important subsidiary site affiliated to Piedras Negras. The details of this evidence follow: Peter Mathews and Stanley Guenter have worked on these inscriptions and have presented a comprehensive reading of it elsewhere (Anaya, Mathews and Guenter 2002), thus I will not deal in great depth with the inscribed text, limiting my discussion on the pertinent details.

First, the two shorter sides of the box the title Ochk’in Kaloomte’, or "West Kaloomte" appears (Figure 5). The title Kaloomte is the highest personal title that is known from the Maya inscriptions, and was given only to a high king.

Second, the name of a high-ranking individual appears mentioned twice. Mathews and Guenter read this name as Tajom U Haab, a quasi identical name as the one appearing on Piedras Negras Panel 2, which reads Tajom U K’ab’ Tuun who also has the title Ochk’in Kaloomte (Figure 6).

In the box the first occurrence of Tajom U Haab’s name is preceded by the glyph yichnal_ "in the presence of…" which normally appears between the name of the local ruler and his overlord. In the second instance the name is preceded this time by the expression u kab’ jiiy, "he supervised it" both expressions imply a hierarchical relationship and are undoubtedly declarations of political subordination (Grube and Martin 1998) (Figure 6, shown above).

The significance of this text for our purposes lies in the implications of political subordination that existed between the local ruler of the valley and the Piedras Negras king. The box itself could have had the same symbolic function that Golden (1998) ascribes to the lintels of La Pasadita, as a means of cementing the relationship between the king and his under lords, which would in turn safeguard the integrity of their domain.

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