Birth seasonality is a time persistent phenomenon that characterizes almost all the populations of the world (Lam e Myron, 1991, 1994; Doblhammer et al. 1999). Despite of this, the causes underlying these seasonal fluctuations still represent an unsolved puzzle. Two main theories have been proposed for explaining birth seasonality. The first one is the "social explanation" which emphasizes the role of social, economic and cultural factors in determining the optimal (from a social point of view) moment  for conception (e.g. the cycle of agricultural workload, religious festivity, marriage seasonality, etc). The second theory is the "environmental explanation" which focuses instead on the role that climatic factors (e.g. temperature, rainfall, light intensity, ect)  play in determining the optimal moment of conception from a biological point of view.
Combining toghether the main interpretative approaches proposed in the literature, we intend to empirically investigate the role of temperature as well as that of marriage seasonality in Italian Regions for a period going from Italian Unification to the eve of the WWII.