PAGES MaGaZINE ∙ VOLUME 31 ∙ NO 1 ∙ May 2023 CC-BY 18 SCIENCE HIGHLIGHTS: AdvANciNg pAst socio–eNviroNmeNtAl systems scieNce The history of societies is influenced by interactions between humans and their environment. This is particularly the case for communities of the high tropical andes, who repeatedly experienced large amplitude changes in climate and the surrounding landscape. Here we present recent underwater archaeo- logical evidence and paleoenvironmental reconstructions compatible with archaeolog- ical timescales. We then focus on identifying and exploring the relation between major environmental changes and cultural innova- tions in the Lake Titicaca region to decipher potential relationships. Lake Titicaca sediment: An archive of past climate change and human activities Lake Titicaca’s sediment record preserves both natural variability and cultural-related signals (Guédron et al. 2021). Multiple stud- ies have reconstructed water-level variability from diverse proxies (e.g. sedimentology, geochemistry, microfossils) and inferred fluctuations in moisture balance at the regional scale (Baker et al. 2001). In general, the temporal resolution of existing paleoen- vironmental studies in Lake Titicaca was not high enough to be compared with archaeo- logical studies. a relatively novel approach in the last de- cade has been underwater archaeological studies which enabled the refinement of the dating of sediment layers at the archaeo- logical timescale by the analysis of ceramic remains found buried in the sediment. For the first time, underwater archaeological remains and artefacts in Lake Titicaca’s sediment have shed light on the impact of water-level variation on human occupation of the land, and revealed the presence of an unknown, and now flooded, cultural land- scape (Delaere 2017; Delaere 2020; Delaere and Guédron 2022) (Fig. 1a–b). Extensive underwater excavations integrating paleoen- vironmental approaches have disclosed the presence of pre-Hispanic port areas (Fig. 1c–d), coastal workshop sites dedicated to manufacturing activities (e.g. leather, stone, and wool) (Fig. 1e), and pastoral and human areas that are currently submerged (Fig. 1f). Ritual offerings have also been identified underwater (Delaere et al. 2019; Delaere and Capriles 2020). These cultural artefacts differ, however, from other remains as they are intentional tributes, and not linked to en- vironmental alteration events. Today, more than 25 underwater archaeological sites, mainly submerged coastal settlements, have been explored in Lake Titicaca (Fig. 1b) us- ing underwater geoarchaeological tools (un- derwater excavations and sediment cores) to better understand the historical interactions between humans (e.g. settlement dynam- ics), and their changing environment (i.e. transgression and regression of the lake). Remnants of both the anthropogenic and natural ecosystems are perfectly intercon- nected and preserved in the lake sediments. Environmental changes and cultural responses at Lake Titicaca The combination of geological and archaeo- logical methods has enabled the develop- ment of a new model of Lake Titicaca’s lake level variations at a resolution compatible with archaeological timescales (Fig. 2) (Guédron et al. 2023). Due to the gentle slopes of the southern Lake Titicaca basin, variation in lake-level of a few meters results in substantial changes in the exposure of sur- rounding land. Hence, over the past four mil- lennia, human communities have witnessed multiple transgressions and regressions (up to ~5 m) of Lake Titicaca that have sub- merged, or opened areas for settlement and agriculture (Fig. 2b) (Delaere and Guédron 2022). yet, ancient native populations in the lake basin undoubtedly had a well-devel- oped knowledge of the local ecosystem and Over the millennia, complex and elaborate cultures have emerged in the Lake Titicaca region. Recent archaeological evidence and new environmental reconstructions spanning the last ~4500 years have enabled us to explore the interactions between cultural developments of past societies and the changing environment. interact ions between past societies and environmental change in the lake ti ticaca region (tropical Andes) Christophe Delaere 1 , S. Guédron 2 and S.C. Fritz 3 doi.org/10.22498/pages.31. 1.18 Figure 1: (A) Location of Lake Titicaca (16°S, 69°W) in the tropical andes. (B) General map of Lake Titicaca with the location of the archaeological sites surveyed since 1950 (black circles), the underwater archaeological sites surveyed between 2012 and 2022 (red circles), and the sediment cores sampled between 2014 and 2017 (dark orange circles). The coastline is defned as the average modern lake level (3810 masl). The civic- ceremonial center of Tiahuanaco is located in the southern part of the basin. (C) Location of fve pre-Hispanic ports discovered between Copacabana Peninsula and the Islands of the Sun and the Moon. (D) Pre-Hispanic navigation artefacts (anchor and ballast stones) discovered underwater at Puncu (PU). (E) Remains of tools belonging to a Tiwanaku stonecutter's workshop discovered underwater in Ok’e Supu (OKE). (F) Remains of a pre-Tiwanaku tomb discovered underwater at Puncu (PU) (Photo credit images D–F: T. Seguin). PERÚ BOLIVIA A 0° 20°S 20°N 40° 60° 40° 80°W B D E F Archaeological sites (200 BCE - 1534 CE) Underwater archaeological sites Sediment cores Tiahuanaco Copacabana Désaguadero Tiquina Lake Titicaca C Island of the Sun C pre-Hispanic port areas 1 2 3 4 5 1. Puncu (PU) 2. Ok’e Supu (OKE) 3. Yampupata (YAM) 4. Sampaya (SAM) 5. Coati (CO) 0 50 Km