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PSYC 3420 Lecture Notes - Mate Choice, Fetus, Parental Investment

Course Code
PSYC 3420
Irwin Silverman

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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
- 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
- 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
- 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
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