L’Expansion d’Homo sapiens

In this keynote, Jean-Jacques Hublin presents a comprehensive overview of the emergence and expansion of Homo sapiens. He begins by highlighting the paradox of our species: widespread and diverse yet genetically homogeneous due to a recent common origin. He then traces the history of paleoanthropological thought, from the outdated multiregional model to the current consensus of an African origin, supported by genetic and fossil evidence. Hublin discusses the 1987 mitochondrial DNA study by Cann, Stoneking, and Wilson, which revealed greater genetic diversity in Africa, and subsequent confirmations from nuclear DNA and Y-chromosome analyses. He emphasizes that the emergence of our species was not a single event but a gradual, pan-African process, as evidenced by the 300,000-year-old fossils from Jebel Irhoud in Morocco. He highlights the cultural and cognitive developments associated with the Middle Stone Age, including symbolic artifacts and ornaments, which indicate increasing social complexity. Hublin also explains the role of climate change and ‘green Sahara’ periods in facilitating early dispersals out of Africa, leading to interactions and interbreeding with Neanderthals and Denisovans. He concludes by noting that while modern non-Africans carry about 2% Neanderthal DNA, natural selection has purged much of it, and the overall pattern is one of replacement with limited gene flow.