Late Formative 2

The changes in the Taraco Peninsula settlement system which took place in the LF2 can only be described as catastrophic and unprecedented. For the first time the region's history, the entire peninsula suffered a population decline. The population index of the peninsula as a whole increased at a rate of -0.12% annually. Figure 7.8 shows that population decline took place across the entire peninsula. The only major village which was spared was the Santa Rosa group, which grew at an annual rate of 0.08% during the LF2.

In other words, the asymmetrical population growth discussed for the LF1 period continued into the LF2, with the Santa Rosa group growing at a rate disproportionate to that of the remainder of the Taraco Peninsula communities. Moreover, the three-tier site size hierarchy first observed in the LF1 continued into the LF2 as well (see Figure 7.6), with basically the same sites occupying each tier.

The difference, however, is that in the LF2 the growth rates of both the center and its tributary villages are much lower than in the LF1. This fact must be considered in light of the phenomenal urban growth that took place in Tiwanaku at this time. In the LF2, Tiwanaku grew to cover perhaps as much as 100 ha, and some of its principal monuments, including the Kalasasaya and the Akapana, seem to have been constructed. Tiwanaku's population growth rate during the LF2 was probably in the range 1% annually. Growth this rapid obviously implies an influx of population from the countryside. Thus, although the settlement determinants on the Taraco Peninsula itself seem to have remained roughly the same as in the LF1, the peninsula was incorporated into a larger system, that of the expanding Tiwanaku polity. The Santa Rosa group no longer occupied the apex of a three-tier site size hierarchy, but rather the second tier of a four-level hierarchy. It had become a regional administrative center of a state. To the existing population growth asymmetries was added a new factor: the draw of a rapidly-expanding urban center.

The population drawn from the Taraco Peninsula actually comprised a significant percentage of the population of LF2 Tiwanaku. The precise percentage can of course never be known. However, if we apply the methods we have used in the Taraco Peninsula analysis to the Tiwanaku case, we can produce a population index value of about 1000 for LF1 Tiwanaku, and 6500 for LF2 Tiwanaku. Given an annual rate of increase (r), an initial population value (I), and a span of years (y), the final population (F) can be calculated as follows:

$$F=I*e^{(ry)}$$

If we assume that the baseline annual population growth rate was 0.10% (an average of MF, LF1 and Tiwanaku population growth rates on the Taraco Peninsula), then the LF1 Tiwanaku population index value of 1000 would have produced a population index of 1221 over the 200 year LF2 period. Thus, Tiwanaku in the LF2 period gained about 5280 population index units over and above what would have been produced by the natural increase of its initial population. That is to say that about $\frac{5280}{6500-1000}$or 96% of Tiwanaku's LF2 population growth resulted from immigration.

Given an initial population of 5581(Table 7.2), the natural increase of the Taraco Peninsula population would have produced a final population of 6817 over the 200 year LF2 period. Therefore, the Taraco Peninsula, through population outmigration, probably to Tiwanaku, lost approximately 2430 population index units relative to what would have been produced by the natural increase of its initial population index value. Therefore $\frac{2430}{5280}$ or about 46% of Tiwanaku's LF2 population influx can be attributed to a flow of population from the Taraco Peninsula communities. Given that the Taraco Peninsula was probably the locus of highest population density in the MF and LF1 in the entire southern Titicaca Basin, this should come as no surprise.