The Bell Beaker complex is defined, above all, by a ceramic style widespread across Europe during the 3rd millennium BC. Its particularly large geographic distribution has provoked different interpretations: a unique population invading Europe, the long-distance exchange of prestige goods, and the absence of a real Bell Beaker population with only the diffusion of its cultural components. For Switzerland, the Bell Beaker period would have developed following influences varying in significance from both the Mediterranean region and Central Europe. Bioanthropology makes it possible to test the first of these hypotheses, which proposes the diffusion of a culture by population displacement. Here, the choice was made to analyze dental nonmetrics. Our previous research on dental nonmetrics supports the idea, for Switzerland, of a certain harmony in Middle Neolithic populations, and the mobility or a moderate population contribution beginning in the Final Neolithic and continuing more intensely during the Bell Beaker period. The aim here is to identify the provenance of the population contribution at the end of the western Swiss Neolithic, and more specifically during the Bell Beaker period. To do so, we have compared the dental morphology of Swiss pre-Bell Beaker, Bell Beaker, and post-Bell Beaker populations with that of contemporaneous populations found not only in the eastern sphere (Czech Republic and Hungary), but also in the southern sphere (southern France and northern Spain). We are now able to demonstrate that the axis for external population influences at the end of the western Swiss Neolithic is clearly southern.