Techno-structural and 3-D geometric morphometric analysis applied for investigating the variability of Holocene unifacial tools in tropical Central Brazil.

During the transition from the Pleistocene to the Holocene and in the early Holocene period, hunter-gatherer communities across tropical South America deployed a range of technological strategies to adapt to diverse environmental conditions. This period witnessed a rich tapestry of technological practices, from enduring, widely disseminated tools to local and sporadically utilized technologies, shaping a multifaceted landscape of technological traditions. Lithic technology during this period was mainly marked by localized sourcing of raw materials, the use of multifunctional tools, a variety of projectile point designs, and the frequently utilization of unifacial shaping technology. In tropical Central Brazil, the Itaparica technocomplex, with unique unifacial lithic tools like limaces, is a pivotal innovation from the Late Pleistocene through the Holocene. However, the factors influencing their morphological and structural variability remain largely unexplored, obscuring our understanding of their ergonomics and their role as mediators between humans and tropical environments. This study hypothesizes that the variability observed within and among unifacial tools from the GO-Ni sites in Central Brazil is a result of a combination of factors, including raw material availability and functional and ergonomic requirements. To test this hypothesis, a study of 67 unifacial tools from this region was conducted, employing techno-structural analysis and 3D geometric morphometrics. This approach was designed to precisely quantify tool geometry and uncover their functional potentials. The analysis revealed significant variability within the techno-structural groups, often intersecting with typological classifications. These results indicate that despite their production attributes, unifacially shaped artifacts demonstrate considerable morpho-structural diversity. The study delineated nine distinct techno-structural groups, each suggesting potentially different functional organizations and deviating from conventional typologies. These results indicate that unifacially shaped artifacts, while embodying a novel technological paradigm of production, exhibit a broader spectrum of variation mainly due to different tool functions. The combined approach adopted in this research highlights on the cultural significance of unifacial tools within Paleoamerican technological systems. It suggests probable unique tool concepts specific to the study area, challenges existing classifications, and enriches our comprehension of early lithic technology in South America.