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Evolutionary explanations of parental investment:
Parental investment is investment which increases a child's chances of survival
at the expense of the parent's ability to invest in other children.
Males produce vast amounts of sperm over a long period of time, incurring few
costs in the way of time or energy. The only restriction on his reproductive ability
is how many females he can mate with and thus, a male's investment is smaller
than a female's. Evolutionarily, a male cannot be sure of paternity and as such
his best strategy for the continuation of his genes is to impregnate as many
women as possible.
A female's investment in her children is much larger than that of a male.
Females produce relatively few eggs in their lifetime, and will be fertile for a far
shorter period of time. The biological cycle of reproduction means that a female
will be indisposed during pregnancy, and as such her best strategy for the
continuation of genes is to indulge in behaviours that increase the chances of
survival for her offspring.
Other explanations of parental investment are:
Paternal Certainty - with internal fertilization, males are more likely to
desert their partner than with external fertilization (IVF treatment in
humans) as they are unsure of the offspring's paternity.
Monogamy - in species where offspring are born at an early stage of
development or where childcare is intensive, pair bonds tend to be
exclusive and long lasting, increasing the chances of the offspring's
Parental Certainty - maternal grandparents are certain a grandchild is
genetically related to them, while paternal grandparents are not. In
keeping with the evolutionary explanation, care and resource allocation
will therefore come from maternal grandparents rather than paternal
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Goss and Shine (1981) report that with internal fertilization parental
care is carried out by females in 86% of species, whereas with external
fertilization parental care is carried out by males in 70% of species,
supporting the predictions based on paternal certainty.…read more