The influence of latitude and cloud cover on the seasonality of human births

Abstract

BACKGROUND: A previous study (Cummings, 2002), hypothesized that human birth seasonality was primarily related to environmental light intensity/photoperiod. PURPOSE: There are two primary goals: to explain seasonality differences between U.S., Canada, and Europe and to test the influence of environmental light intensity/photoperiod at divergent latitudes. METHODOLOGY: Existing seasonality data were extracted from previous studies at various locations throughout the world. Daily cloud cover amounts (clearness) were utilized as indices for environmental light intensity. DISCUSSION: Results were evaluated and discussed for each sub-study. CONCLUSION: Sub-study results support the hypothesis that human birth seasonality may be influenced by environmental light intensity and photoperiod. This conclusion is supported by logical links between increased light intensity/photoperiod and conceptions at different latitudes. Irrefutable proof may involve correlating long term changes in cloud cover with long term changes in human birth seasonality.