The dispersion of the LBK agro-pastoral system through western Europe is explored in terms of three related aspects : local demography, segmentation processes and densification / expansion. The local demographic signals are briefly reviewed and form the basis of a presentation of socio-economic and ideological mechanisms which might have supported this neolithic trajectory. Based on a demic expansion model, this approach suggests a good fit between the archaeology and the ethno-sociological models considered. Yet the issue of long-distance movements, together with the occasionally rapid pace of expansion, requires one to call upon additional bio-environmental and / or ideological mechanisms, including a largely speculative hypothesis: the transmission of the LBK system to some indigenous people. Although traces of this potential promiscuity are very discreet in the available data, as are the natives themselves, indigenous adoption would have contributed to the demic expansion and enhanced its dynamics and variability. Nevertheless, the sustainability of this socio-cultural system suggests that such an enlargement would not have led the process but only contributed to its adaptative longevity. A current project (ANR-09-CEP-004-01, "Obresoc") seeks to use the tools discussed here, among many others, in a simulation of this specific prehistoric trajectory.