[Child mortality in the past: beyond appearances]

The purpose of the article is to give a short synthesis of the communications gathered in this volume dedicated to the topic of child mortality. It starts with the evocation of some key issues about sources and methods: the study of mortality before 5 years appears more difficult than expected. The trend of the decrease, more and more clear, though unlinear, suggests that climate, beyond environmental and socio-economic factors, may have been an underestimated factor so far. The analysis of causes refers to the concept of synergy, several factors acting simultaneously to reinforce the previous trends, either of decrease or increase of death risks.