Imprinting occurs only in mammals, and why it should exist at all is a mystery. One gene that is imprinted in most mammalian species is Igf2 gene, whose product - insulin-like growth factor-2 - is required for prenatal growth. Most mammalian females can mate with multiple males, generating multiple embryos with different fathers in each litter. If one father had an Igf2 allele that caused more rapid prenatal growth, embryos carrying his genes, it would prosper at the expense of the other embryos. While this would be good for the father's genes (in an evolutionary sense), it would drain the resources of the mother, potentially putting her life at risk (not good for her genes). Thus, it is in the mother's interest to counter these paternal effects with maternal changes that limit the growth of the embryo. Based on this scenario, decide whether the Igf2 gene is more likely to be imprinted in the male or in the female.