Towards an interdisciplinary perspective for the study of human expansions and biocultural diversity in the Americas

The timing and mode(s) of the initial human occupation of the Americas are among the most discussed topics in archaeology and biological anthropology, with hundreds of articles published in the last decades dedicated to the topic (for some comprehensive reviews, see References 1–3). Researchers have contributed to the debates through a vast range of disciplines, methodological and theoretical approaches, ranging from traditional archeological and bioarchaeological methods, to climate simulations and ancient DNA analyses. And yet, despite recent advances in the study of the biological variation and prehistoric expansions of populations into and within the Americas, there is still little consensus about key questions including the time and modes of human dispersion across the continents. This brings up a crucial question: why are we unable to find a consensus about the processes behind the initial settlements of the Americas? There are certainly multiple factors contributing to our inability to build reliable interpretations on this topic. Some of them are common to all endeavors to reconstruct and study past human societies across the planet, and some are unique to the history of research in the Americas. As a result, it is not uncommon to find significant reevaluations of current models and hypotheses, either through new findings and new methodological innovations (see, e.g., the most recent findings of early footprints in New Mexico), by the reanalysis of radiocarbon data accumulated over decades of research, or due to new theoretical framings of available data (see Reference 6 as a good example). While these constant reevaluations of the origins of early inhabitants of the Americas are related to all aspects of this process (e.g., chronology, cultural diversity, adaptation, and biological diversity), here we focus on recent discussions about the origins of Native American biological diversity, which by itself has been the focus of a vast and prolific literature. The study of biological diversity among early Native Americans has progressed at a remarkably fast pace in recent decades, and researchers new to this topic will probably find the process of reviewing the body of specialized literature daunting. Recent studies have drawn upon a wealth of different modern sources of information, including molecular (Y-chromosome, mitochondrial-DNA, autosomal markers), morphological (cranial, dental, and postcranial), and cultural (linguistic, lithic technology, and physical activity) data. The rapid incorporation of cutting-edge methods in the last decades has brought to the research of the early peopling and diversity of the Americas the sequencing of whole ancient genomes, registering high-quality morphological data with 3D surface and CT-scanners, performing digital reconstructions of fragmented anatomical structures, as well as accessing and sharing a large amount of data thanks to Big Data and Open Science initiatives. However, while these methodologically advanced studies are bringing new sources of information to the discussion, they have also siloed most of the discussions within the confines of specialized subdisciplines, limiting the dialog between researchers from different backgrounds. Indeed, there are only a handful of projects that have taken advantage of multidisciplinary perspectives. Consequently, recent discussions about the biological variation and migratory patterns of early Americans are mostly restricted to (re)interpretations of a few former models and rarely integrate discussions derived from analyzing different kinds of evidence. Evidently, this limitation can be largely explained as the result of the progressive degree of academic specialization required to handle each data type, as well as the substantial expertise and financial support needed to carry them out. Because of this natural tendency of specialization, we have reached a moment in which it is crucial to promote more dialog among research groups and stakeholders and integrate frameworks combining cultural, genetic, and morphological data to study migratory patterns and biological diversity among Native Americans. With this shared goal in mind, the authors participated in an interdisciplinary symposium in the context of the 90th Annual meeting of the American Association of Physical (now Biological) Anthropologists (Figure 1). The symposium focused on debating how different kinds of evidence contribute to discuss various aspects of the origin and expansions of human populations across the Americas and included experts representing diverse career stages, gender, ethnicity, as well as different countries of origin. The diverse panel of specialists enriched the discussions by contributing their own perspectives from both South, Central, and North American backgrounds. The lessons learned from discussions held at the symposium, and the fact that all participants share the feeling that more interdisciplinary dialog is needed, prompted us to write this overview article. We had the opportunity to share ideas with specialists working with cranial morphology, dental metrics and non-metrics, linguistics, and DNA from prehistoric and/or extant populations, as they discussed their current work on ancient expansions and biocultural diversity in the Americas. While these disciplines cover only a fraction of research topics and disciplines focused on the human occupation of the Americas, the work presented highlights a series Received: 10 December 2021 Revised: 20 December 2021 Accepted: 28 December 2021