Bull. Tohoku Univ. Museum. No. 20, pp. 21‒40, 2021 © by The Tohoku University Museum Stone Tool Functions in the Preceramic Period at the Loma Atahualpa Site in Ecuador Yoshitaka Kanomata 1) , Andrey V. Tabarev 2) , Alexander N. Popov 3) , Boris V. Lazin 3) , Tatiana A. Gavrilina 2) , Maxim K. Rudenko 3) and Jorge G. Marcos 4) 1) Tohoku University, Sendai, Japan 2) Institute of Archaeology and Ethnography, Novosibirsk, Russia 3) Fareastern Federal University, Vladivostok, Russia 4) Escuela Superior Politécnica del Litoral, Guayaquil, Ecuador Abstract: The excavations at the Loma Atahualpa site (Atahualpa-66) in the Santa Elena Province of Ecuador were conducted by Russian, Ecuadorian, and Japanese archaeologists in 2017 and 2018. Three human burials were discovered approximately 100 cm below the ground surface, indicating that they probably originated from the Late Las Vegas culture of the preceramic period. This study aims to understand the technological and functional features of stone tools from the preceramic period at the Loma Atahualpa site. In addition, technological and functional changes between the Early-Middle Las Vegas and Early Valdivia cultures were examined in comparison to the materials already analyzed. 1. Introduction Since the late 1950s, the earliest pottery has been attributed to the materials of the Early Formative Valdivia culture in coastal Ecuador. The Real Alto site, one of the most signifcant sites of the Valdivia culture, was excavated in the 1970s and 1980s. A series of field studies provided extensive and precise information on the evolution of small sites of early agriculturalists into huge settlements with artificial mounds and plazas and, later, into one of the earliest regional ceremonial centers in South America (Marcos 1988). Unfortunately, intensive expeditions of Valdivia culture sites were interrupted after the mid-1980s. Consequently, several important archaeological questions have remained unanswered for approximately 30 years. In 2014, 2015, and 2017, new excavations of the Real Alto site were conducted by Russian, Ecuadorian, and Japanese archeologists (Popov et al. 2017). The main goal of their research was to discover the oldest cultural layer containing Valdivia I and San Pedro pottery in the early ceramic period. At last, the authors discovered the oldest non- ceramic culture at the Real Alto site, dated around 5,800 BP (6655-6563calBP). In addition, numerous lithic artifacts were unearthed and analyzed based on techno-typology and use- wear (Tabarev and Kanomata 2015, Kanomata et al. 2019b). The authors proposed the original model of the “Tropical package” for the transitional period from hunter-gatherers to early agriculturalists in coastal Ecuador. Moreover, the new radiocarbon dates of Valdivia I and San Pedro potteries (n =5) could be attributed to 4640 to 4450BP (5470-4880calBP) (Tabarev et al. 2016, Kanomata et al. 2019b). In the case of the Santa Elena Peninsula, we suggest the existence of pre- Valdivia without pottery as well as Las Vegas with pottery. The next target was to understand the dates and features of the Late Las Vegas culture. 2. New Excavation at the Loma Atahualpa Site A small test pit was excavated at the Loma Atahualpa site (Atahualpa-66) in Santa Elena Province in October 2017, in which a human burial was discovered 95cm below the ground surface. The burial was attributed to the preceramic period because this cultural level contains no pottery. Accelerator Mass Spectrometry (AMS) dates were obtained from the charcoal samples situated 80–100 cm below the ground surface (Table 1). A radiocarbon date near the burial indicated a preceramic age (5,340±30BP) and another, farther away from burial, yielded a younger age (3,280±30BP). Based upon these results, the burial can be attributed to the Late Las Vegas culture, and this site is deemed the most suitable target to achieve our research goal. In 2018, the second excavation was directed by J. G. Marcos, A. N. Popov, and A. V. Tabarev. This project was