The Divided Child
My mother’s kin are not my father’s kin. This asymmetry results in conflicting selective forces acting on genes of maternal and paternal origin revealed in the phenomenon of genomic imprinting. Genes of paternal origin in a child are predicted to favor benefits to the child but reproductive costs to the child’s mother (or other matrilineal kin) whereas genes of maternal origin are predicted to favor benefits to the child’s mother. These intragenomic conflicts with be illustrated with disorders of imprinted gene expression. Beckwith-Wiedemann and Silver-Russell syndromes provide evidence that genes of paternal origin promote, and genes of maternal origin restrain, fetal growth. Prader-Willi syndrome provides evidence of evolutionary conflicts associated with breastfeeding and infant sleep.