The Role of Mobility in Human Evolution: An Investigation Among Central African Hunter-Gatherers

Mounting genetic, archaeological, paleoanthropological and paleoenvironmental evidence over the past few decades have centred theories of Homo sapiens origins in Africa. This has unleashed heated debates about the timing and place, within the continent, where our species emerged. However, recent research has highlighted that rather than in a single place, Homo sapiens originated and diversified within strongly subdivided populations living in different parts of Africa that would have come into contact at different points in time, and in doing so exchanging genes and culture. Thus, situating the causes and consequences of ancient patterns of human mobility at the core of human evolutionary questions. Yet, the scarcity of research in key parts of the African continent, and the lack of integration of archaeological, paleoanthropological, cultural and genetic data with one another and within spatially explicit environmental frameworks has left important gaps in our knowledge. These include determining when exactly periods of connectivity and isolation between different parts of Africa would have taken place, what environmental, social or demographic processes promoted them, and their precise consequences for modern human biological and cultural evolution. Given that humans have lived as mobile hunter-gatherers throughout the vast majority of our history, this dissertation sets to address such gaps in knowledge by focusing on the largest and most diverse group of hunter-gatherers in the world, living in the Congo River Basin. By bridging the gap between contemporary and prehistoric hunter-gatherer populations living in the region, I directly relate the behaviour of contemporary people to the continental-level patterns leaving the traces we can observe in the archaeological and fossil record. Hence, offering us a lens into the lives of our ancestors and the ways in which they managed to thrive first within and then outside of the African continent. In Chapter 2, I first investigate the ecological, climatic and geographic factors driving population dynamics and interconnectivity between hunter-gatherers across Central Africa over the past 120,000 years by means of Environmental Niche Models. This is followed by Chapter 3, where I explore the consequences of changing population dynamics and environmental heterogeneity for structuring the tremendous cultural, linguistic, and genetic diversity observed among hunter-gatherers inhabiting the region today. Chapter 4, on the other hand places its lens on the archaeological record, and too examines the social and ecological processes shaping it – relating past and present cultural dynamics and their drivers. Chapter 5 shifts the scale of analyses from the population to the individual level, and characterises the full geographical range of the Mbendjele BaYaka hunter-gatherers from the Republic of Congo, and the factors influencing their mobility decisions. This is essential to understand how individual behaviours scale up to continental level patterns. Chapter 6 builds on the findings from Chapter 5 and explores how Mbendjele’s mobility patterns structure their social worlds. In doing so, it offers a glimpse into how individuals’ spatial decisions derive in the unique system of social organization we observe in hunter-gatherer societies, and that has been shown to be responsible for some of the key derived features of our species. I conclude the dissertation by discussing how shedding light on the interplay between environmental factors, individual mobility decisions and population dynamics is vital for determining the drivers of human cultural and biological evolution. On top of it, by emphasizing how developing methodologies that allow the integration of multiple lines of evidence, including environmental, archaeological, paleoanthropological, and ethnographic data, is instrumental for this endeavour.