One hypothesis suggests that evolutionary change is facilitated by environmental sensitivity of development and the associated modifications of organismal development that induce selectable phenotypic variation. My research identified a role for developmental timing in generating plasticity-driven diversification of the shrew mandible and physiological mechanisms of sex-specific maternal effects in birds. Current work focuses on the genomic and physiological mechanisms that translate maternal stress into an embryonic growth response in birds and the molecular mechanisms that underlie variation in ossification timing in the mammalian skeletal structures.