Par : Frédérik Saltré
du 2023-01-11 - 11:00 au 2023-01-11 - 12:00

Grand Amphi Pasteur

Résumé : Australia is the world’s driest inhabited continent and represents one of the greatest of humanity’s achievements: rising to the challenge of thriving in an arid continent > 50,000 years ago. At the time anatomically modern humans first set foot on the continent we call ‘Sahul’ (the combined continent including mainland Australia, New Guinea, and Tasmania during periods of much lower sea level than today), the ecosystems and climate they encountered were very different from what we experience today, yet not necessarily unknown. However, our lack of understanding of how these ancient people arrived and succeeded in making a living in one of toughest environements on Earth is rivalled only by our limited knowledge of how they subsequently shaped Sahul’s ecosystems. Indeed, shortly after human arrival in Sahul, where a rich assemblage of large vertebrates (up to three tonnes) once lived, there was a rapid loss of every single native terrestrial animal larger than about 40 kg. Most of these species were hervivores, meaning that their loss likely modified the entire ecosystem through different feedbacks, although the degree to which this occurred is still debated. Good data describing these relationships are rare, and inferences are often biased in space and through time because of differential preservation of the older evidence. In this seminar, I will introduce how new statistical approaches and recent models of the population dynamics of ancient humans coupled with fossil records, archeological data, and palaeoclimate simulations have shed new light on the origins and ecological consequences of the initial peopling of Sahul. I will i) show how environmental conditions shaped the patterns of initial expansion of anatomically modern humans worldwide, ii) discuss the most likely places where these first people would have landed on Sahul’s shores and iii) provide new insights on the causes of megafauna extinctions resulting from intricate and synergistic effects between these first people and variable climate conditions. En français, Grand Amphi Pasteur du CEREGE, aussi visible en streaming.