The center cannot hold: A Bayesian chronology for the collapse of Tiwanaku

The timing of Tiwanaku's collapse remains contested. Here we present a generational-scale chronology of Tiwanaku using Bayesian models of 102 radiocarbon dates, including 45 unpublished dates. This chronology tracks four community practices: residing short- vs. long-term, constructing monuments, discarding decorated ceramics, and leaving human burials. Tiwanaku was founded around AD 100 and around AD 600, it became the region's principal destination for migrants. It grew into one of the Andes' first cities and became famous for its decorated ceramics, carved monoliths, and large monuments. Our Bayesian models show that monument building ended similar to AD 720 (the median of the ending boundary). Around similar to AD 910, burials in tombs ceased as violent deaths began, which we document for the first time in this paper. Ritualized murders are limited to the century leading up to similar to AD 1020. Our clearest proxy for social networks breaking down is a precise estimate for the end of permanent residence, similar to AD 1010 (970-1050, 95%). This major inflection point was followed by visitors who used the same ceramics until similar to AD 1040. Temporary camps lasted until roughly similar to AD 1050. These four events suggest a rapid, city-wide collapse at similar to AD 1010-1050, lasting just similar to 20 years (0-70 years, 95%). These results suggest a cascading breakdown of community practices and social networks that were physically anchored at Tiwanaku, though visitors continued to leave informal burials for centuries. This generation-scale chronology suggests that collapse 1) took place well before reduced precipitation, hence this was not a drought-induced societal change and 2) a few resilient communities sustained some traditions at other sites, hence the chronology for the site of Tiwanaku cannot be transposed to all sites with similar material culture.