A Simpson diversity index was computed for the Wall and Fredricks site assemblages as well as for nut types. Based on equal numbers of samples from each site, diversity values for the Wall and Fredricks sites are quite close (.8384 and .8812, respectively). Both are also high, indicating relatively heterogeneous assemblages. The Fredricks site assemblage is somewhat more diverse than that of Wall; however, the difference is not as great as might be expected considering the fact that 23 taxa are represented at Fredricks, compared with only 12 from Wall. This finding indicates that the relatively high Wall site index reflects greater equitability of representation of plant taxa in that assemblage. The Fredricks site assemblage, on the other hand, is richer.
One interpretation of these results is that more plant resources were used during the later occupation but that there was a concentration on exploitation of only a few of these. Although these findings must be considered highly tentative, diversity indices may prove to be useful tools for interpreting subsistence remains, with appropriate attention to potential sources of bias (Wilson 1983). Since ecologists working with observable organisms often disagree on the meaning and proper use of diversity indices (Peet 1974), archaeologists must exercise extra caution in using them.