title: A sex-specific test of selection in utero.
abstract: We find support for the hypothesis that changes in the monthly odds of a twin among live-born males predict subsequent and opposite changes in the odds of a twin among live-born females. The hypothesis arises from the long standing argument that natural selection has conserved mechanisms by which pregnant women in stressed populations spontaneously abort fetuses least likely to yield grandchildren. Previous attempts to empirically test this argument focus almost entirely on males. We contribute to the literature by showing that, consistent with the logic of natural selection, maternal adaptations to environmental changes likely have effects on the survival of both male and female conceptuses and fetuses.
authors.affiliation: School of Public Health, University of California at Berkeley, 50 University Hall, Berkeley, CA 94720-7360, USA. rayc@berkeley.edu
authors.forename: Ralph A
authors.initials: RA
authors.lastname: Catalano
authors.forename: Katherine
authors.initials: K
authors.lastname: Saxton
authors.forename: Tim
authors.initials: T
authors.lastname: Bruckner
authors.forename: Sidra
authors.initials: S
authors.lastname: Goldman
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Anderson
mesh_terms: D000022:Abortion, Spontaneous / Q000453:epidemiology / Q000235:genetics*; D002140:California / Q000453:epidemiology; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D008297:Male; D011247:Pregnancy; D011272:Pregnancy, Multiple / Q000235:genetics*; D012641:Selection, Genetic; D012744:Sex Ratio; D014427:Twins / Q000235:genetics