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PSYC 3420
Irwin Silverman

Chapter 7: Problems of parenting - From an evolutionary perspective, offspring are a sort of vehicle for their parents. They are the means by which their parents’ genes may get transported to succeeding generations - Evolution, in short, should produce a rich repertoire of parental mechanisms specially adapted to caring for offspring - Given the costs of parental care, it is reasonable to expect that whenever we do observe parental care in nature, the reproductive benefits must be large enough to outweigh the costs - An example of adaptations for parental care is found in nesting birds - Tinbergen (1963) explored the puzzle of why nesting birds would go to the trouble of removing the broken shells from their newly hatched chicks, taking them piece by piece far away from the nest - Tinbergen discovered that only the protection from predator’s hypothesis received support. The cost of parental support care was outweighed by the benefits of increased survival of chicks through a decrease in predation - Solo’s mother risked her life and limb to save her pups, while the father stood by passively and did nothing to protect them. Throughout the animal kingdom, females are far more likely than males to care for their offspring - Two hypotheses have been advanced to explain female parental care - 1. The paternity uncertainty hypothesis - Means that from a male perspective there can always be some probability that another male has fertilized the female’s eggs - Paternity uncertainty is strongest in species with internal female fertilization, including many insects, humans, all primates and all mammals - Because of internal female fertilization, when a male comes on the scene, the female may already have mated with another male and so her eggs might already be fertilized - But it does make it less profitable for fathers, compared to mothers, to invest in their offspring - 2. The mating opportunity cost hypothesis - This stems from sex differences. Mating opportunity costs are missed additional mating as a direct result of effort devoted to offspring - While a mother is gestating of breastfeeding her child or a father is fending off predators, neither has high probability of securing additional mates - When males do not suffer mating opportunity costs as a consequence of investing in offspring, conditions are ripe for the evolution of male parental care - We can predict that men will be more likely to invest in children in contexts in which there is a surplus of men but will be more negligent of children when there is a surplus of women - In addition to sex ration, other factors likely to explain individual differences in amount of parenting include; 1. Attractiveness of the male as a short term mate (more attractive males are predicted to reduce their parental effort and increase their mating effort) 2. Population density (large cities provide more opportunities for males to interact with females) An evolutionary perspective on parental care - Selection will favour adaptions for parental care, the preferential allocation of investment to one or more offspring at the expense of other forms of allocating investment that have the effect of increasing fitness of the parent - It follows that mechanisms of parental care will favour some offspring over others, a condition called parental favouritism. Stated differently, selection will favour the evolution of mechanisms in parents that favour offspring who are likely to provide a higher reproductive return on the investment - At most general theoretical level, evolved mechanisms of parental care should be sensitive to three contexts; - 1. Genetic relatedness of offspring (Are the children really my own?) - A men has at least two sources of information to consider the likelihood that he is the genetic father of a given child: 1) information about his partner’s sexual fidelity during the period in which she conceived 2) perceptions of the child’s resemblance to him - Success in promoting the man’s belief that he is the father should increase his willingness to invest in that child - Men’s perceptions of their children’s resemblance to themselves also might affect family violence - Thus perceptions of one of the critical cues that affect both his degree of investment in the children and the magnitude of the costs he inflicts on is spouse - 1) men will allocate more resources to their genetic children than to their stepchildren 2) men who are uncertain about their children will invest less than men who are certain 3) men will invest more in children when the child’s mother is their current mate - Genetic relatedness to a child is a powerful predictor of men’s monetary investment - Data show that children living with one genetic parent and one stepparent are roughly forty times more likely to be physically abused than children living with both genetic parents - The rates of child murder are clearly far higher for stepparents than for genetic parents. The risk is highest for very young children, particularly for children age 2 and under - Nonetheless, the greater average genetic relatedness of mothers than fathers to their children due to some level of uncertainty of paternity suggests that women will be more invested in their children, on average, than will men - 2. Offspring
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