title: Solar activity at birth predicted infant survival and women's fertility in historical Norway.
abstract: Ultraviolet radiation (UVR) can suppress essential molecular and cellular mechanisms during early development in living organisms and variations in solar activity during early development may thus influence their health and reproduction. Although the ultimate consequences of UVR on aquatic organisms in early life are well known, similar studies on terrestrial vertebrates, including humans, have remained limited. Using data on temporal variation in sunspot numbers and individual-based demographic data (N = 8662 births) from Norway between 1676 and 1878, while controlling for maternal effects, socioeconomic status, cohort and ecology, we show that solar activity (total solar irradiance) at birth decreased the probability of survival to adulthood for both men and women. On average, the lifespans of individuals born in a solar maximum period were 5.2 years shorter than those born in a solar minimum period. In addition, fertility and lifetime reproductive success (LRS) were reduced among low-status women born in years with high solar activity. The proximate explanation for the relationship between solar activity and infant mortality may be an effect of folate degradation during pregnancy caused by UVR. Our results suggest that solar activity at birth may have consequences for human lifetime performance both within and between generations.
authors.affiliation: Department of Biology, Norwegian University of Science and Technology (NTNU), Trondheim, Norway gine.skjarvo@bio.ntnu.no.
authors.forename: Gine Roll
authors.initials: GR
authors.lastname: Skjærvø
authors.affiliation: Department of Biology, Norwegian University of Science and Technology (NTNU), Trondheim, Norway.
authors.forename: Frode
authors.initials: F
authors.lastname: Fossøy
authors.affiliation: Department of Biology, Norwegian University of Science and Technology (NTNU), Trondheim, Norway.
authors.forename: Eivin
authors.initials: E
authors.lastname: Røskaft
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D002675:Child, Preschool; D005260:Female; D005298:Fertility / Q000528:radiation effects*; D049670:History, 17th Century; D049671:History, 18th Century; D049672:History, 19th Century; D006801:Humans; D007223:Infant; D007226:Infant Mortality; D007231:Infant, Newborn; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D009664:Norway; D012098:Reproduction / Q000528:radiation effects; D012189:Retrospective Studies; D019445:Solar Activity; D014466:Ultraviolet Rays / Q000009:adverse effects*; D055815:Young Adult
keywords: early conditions; fitness; humans; individual-based demographic data; life history; ultraviolet radiation