Using the multidisciplinary forces of the CNRS, the author defines an early group of colonisers in the northern Alps as the glaciers retreated. At the key site of La Fru, analysis of the lithics shows an assemblage characterised by microblades made from good quality flint supplied from sources a hundred or more kilometres away. Analogies with early assemblages in Beringia and in Britain suggest this may be identified as a pioneer phase. Later in the Magdalenian, the supply is more varied and regional, generating networks for the dissemination of new ideas.