The Amazonia region in South America is an enormous area of genealogical diversity. We spoke to Professor Nick Emlen, Professor Rik van Gijn and Dr Leonardo Arias, organisers of a new Interface Focus issue on this topic. They explained the importance of utilizing different approaches and crossing disciplinary boundaries to gain insights into the human past of Amazonia.
1. What is the focus of this issue?
This issue is about the human history of Amazonia, as seen through interdisciplinary collaborations among scholars from different research fields, including anthropology, linguistics, archaeology, genetics, (ethno-)history, and biogeography. Bringing these fields together can tell us more about the human dynamics of the Amazonian past than what we can learn from any of them individually; nonetheless working between such distinct fields, with different methods and approaches, presents formidable challenges. The articles in this issue bridge disciplinary boundaries with these goals and challenges in mind.
2. South America has a curious linguistic landscape. Could you tell us more about what is intriguing?
Indeed, a striking fact about the indigenous linguistic panorama of South America is its very high degree of genealogical diversity. That is, many of the continent's languages belong to small language families (in addition to a few continent-wide families); these small families include around 64 families with only one member (so-called language isolates), which account for around one third of all such languages around the world. Linguists have long struggled to explain this high degree of genealogical diversity in South America, given that the continent is one of the most recent regions to be inhabited by humans. One of the most promising ways to clarify this situation is through collaborations among researchers from different fields, such as linguistics, genetics, biogeography, and anthropology, as demonstrated in the article by van Gijn, et al. .
3. How does research in this field bring together different disciplines, and what are the benefits of such collaborations?
The academic disciplines listed above have become increasingly specialized in recent decades, and each of them has developed new methods, sophisticated analytical techniques, and massive amounts of empirical data. This has led to great new insights in each discipline, but it has also made it more difficult than ever to work across the disciplines to create integrated, multi-disciplinary historical accounts. For instance, areal linguistic typology has become a very technical field in recent years, with large datasets and new statistical methods that can be used to detect fine-grained patterns in linguistic structure that suggest historical contacts among populations. Genetics also now draws on unprecedented quantities of data and novel techniques to identify similar phenomena. Each of these fields tells us something different about the human past, but bringing those data and analyses together in a principled way is very complex and difficult. With this sort of challenge in mind, the contributors to this issue were asked to reach across disciplinary boundaries and try to answer a specific question using the data, methods, or theories from more than one discipline. For instance, Michael et al.  used dated archaeological sites around Amazonia as calibration points for a phylogeny of the Arawakan language family and a timeline of its expansion, contributing insights to both linguistics and archaeology that would not otherwise be possible.
4. What are the most important questions for future research in this field?
The multidisciplinary study of the human past has emerged as an important focus of research in recent years. However, there remains a need to develop new methodological approaches that account for the distinct types of empirical evidence and the different analytical approaches that disciplines use as they explore the human past. Furthermore, a central problem in understanding the human past is explaining patterns of diversity – that is, accounting for the origin and maintenance of diversity in material culture, cultural practices, language, genetics, landscape transformation and domestication, etc. This is especially true of Amazonia, which is one of the most diverse and least scientifically understood continents. In addition, understanding the history of human societies in Amazonia is of great scientific and societal relevance as it has become increasingly clear that successful conservation efforts must go hand in hand with indigenous and local communities .
 Van Gijn R, Norder S, Arias L, Emlen N. Q., Azevedo M. C. B. C., Caine A, Dunn S, Howard A, Julmi N, Krasnoukhova O, Stoneking M and Wiegertjes J. 2022. The social lives of isolates (and small language families): the case of the Northwest Amazon. Interface Focus. 13: 20220054. (doi: 10.1098/rsfs.2022.0054)
 Michael L, de Carvalho F, Chacon T, Rybka K, Sabogal A, Chousou-Polydouri N and Kaiping G. 2022. Deriving calibrations for Arawakan using archaeological evidence. Interface Focus. 13. 20220049. (doi: 10.1098/rsfs.2022.0049)
 Dawson, N. M., B. Coolsaet, E. J. Sterling, R. Loveridge, N. D. Gross-Camp, S. Wongbusarakum, K. K. Sangha, L. M. Scherl, H. Phuong Phan, N. Zafra-Calvo, W. G. Lavey, P. Byakagaba, C. J. Idrobo, A. Chenet, N. J. Bennett, S. Mansourian, and F. J. Rosado-May. 2021. The role of Indigenous peoples and local communities in effective and equitable conservation. Ecology and Society 26(3):19. (doi: 10.5751/ES-12625-260319)
Image credit: Reflecting on the past along the Atabapo River. Leonardo Arias.