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Discuss sex differences in Parental Investment (24 marks)
Parental investment is defined as "any investment made by the parent in an individual offspring that
increases the offsprings chance of survival." There are differences in how much each gender invests in
their offspring, according to evolutionary theories.
Female investment in a child is usually greater. This is because female's can have limited offspring,
whereas men can have potentially an unlimited offspring, as well as this, females also make a greater
pre and post natal commitment. The female must carry and nourish the child for 9 months, and then
continue breastfeeding and care for the baby once it is born, as the child cannot get this care from the
male, the male's investment is much less, as the male can "opt out" where the mother cannot. The
investment made by mothers is also great, as human babies are more dependant and require more
care, as they are born less developed than other species.
A reason why male investment is less of that than females is because males are always at risk of
cuckoldry investing resources in another man's child where females are always certain the child is
theirs. Therefore the males invest less in the child, to reduce the risk of cuckoldry and therefore reduce
potential resource wasting. Additionally, the risk of cuckoldry means there is more concern from the
males over the sexual fidelity of mates, so as their investment is well spent. Conversely, a women's
concern is more prominently over emotional fidelity, as they want to increase the male investment in the
child, so the child has good resources, which increases the chance of offspring survival.
However there are some problems with this explanation of sex differences. One key flaw is that is offers
no explanation for why some women desert their children after birth or in some cases commit
infanticide, these two situations demonstrate that the mother is not always keen to make an investment
in their child, refuting the theories of sexual selection. However, this can be explained as an adaptive
response, the protectiveness is switched off by environmental challenges eg. women is living in poverty
or is shamed for having child.
As well as this, it is also a post hoc explanation, and therefore the theory of parental investment is
difficult to falsify and is also open to questions of scientific rigour. It also means it is difficult to apply to
An example of such modern relationships is the fact that cuckoldry is very commonplace in many
societies (particularly in the West), and is not seen as the problem this theory sets it out to be. Anderson
rejects evolutionary ideas and found that men did not discriminate financially between a child who was a
step child in a current relationship, compared to their own child from a previous relationship. This shows
that cuckoldry is not a problem in many modern societies, and therefore the explanation for sex
differences is determinist in assuming a father will avoid making an investment in others children. It also
demonstrates how parental certainty is not always an issue for human males. However this could be
explained by sexual strategies theory, men may invest in a step child in order to convince the mother
that he is a good provider therefore promoting future mating opportunities.
As well as this, basing paternal investment on environmental factors alone is very limiting. This is
because men's parental behaviour depends on various personal and social conditions including the
relationship with the mother, the male personality and the child's personality. As well as this,
experiences such as divorce correlate with the degree of male investment. This demonstrates that
parental investment theories are limited explanations, and determinist for assuming that evolutionary
factors will always influence the amount of male investment.
However, there are studies, which show that cuckoldry has many benefits for females, as they receive
more resources and possibly better genes for their offspring, which offsets their parental investment.
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This shows how women make a greater investment in their offspring, as they risk abandonment or
maleretention strategies by their current partner to have a `better' and more protected offspring.
As well as this, the theory is very reductionist, as it does not seek to explain why mothers make a great
investment in adopted children, as in many cases, they don't require feeding and haven't been carried.
As well as this, it doesn't explain the investment made in children in homosexual relationships, eg.…read more