Parents can induce considerable variation in traits expressed by their offspring by varying the quantity and quality of nourishment they provide during development (e.g.Thorogood et al 2011), including traits that are not expressed until adulthood (e.g. Walker et al 2013). This is particularly evident from our (as yet unpublished) work on burying beetles. Our experiments therefore suggest that much of the individual variation upon which natural selection acts originates from variation in parental care received as an offspring.
Thorogood, R. et al 2011 Sense and sensitivity: responsiveness to offspring signals varies with parents’ potential to breed again. Proc R Soc B 278:2628-2645
Walker, L. K. et al 2013 A window on the past: male ornamental plumage reveals the quality of their early life environment. Proc R Soc B 280:20122852