title: 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.
  
  
  OBJECTIVE
  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.
  
  
  METHODS
  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.
  
  
  CONCLUSIONS
  Results were evaluated and discussed for each sub-study.
  
  
  CONCLUSIONS
  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.
authors.affiliation: bynehill@aol.com
authors.forename: David R
authors.initials: DR
authors.lastname: Cummings
mesh_terms: D001723:Birth Rate / Q000639:trends*; D005260:Female; D005306:Fertilization; D005843:Geography; D006801:Humans; D008027:Light; D010507:Periodicity; D011247:Pregnancy; D012621:Seasons; D013997:Time Factors; D014887:Weather