Discuss Sex Differences in Parental Investment

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Trivers defined parental investment as “any investment by the parent in an individual offspring that increases the offspring’s change of surviving (and hence reproductive success) at the cost of the parent’s ability to invest in other offspring”. Maternal investment is much larger than paternal investment. Females make a greater biological investment than males because they produce far fewer egg cells than males produces sperm, and egg cells are far more costly to produce. This means that females require a greater initial investment because they can only have a limited number of offspring, whereas a male can potentially have an infinite number of children. As a result of this inequity, females are choosier in who they mate with. As well as making a larger prenatal investment, mothers must also make a larger postnatal investment. Another reason for the high maternal investment is that mothers form an attachment to their child through the act of breastfeeding. The greater investment of females may also be explained in terms of parental certainty. Because fertilisation in humans is internal, the female is always certain that she is the mother of her child. The male, on the other hand, must always have some degree of parental uncertainty; this is known as cuckoldry. Males are under pressure to protect themselves from investing in a child who is not genetically their own, and thus may be more reluctant to invest heavily in the child. The possibility of sexual infidelity posed different adaptive problems for males and females. A man whose mate was unfaithful risked investing in offspring who were not his own, while a woman with an unfaithful mate risked the diversion of resources away from her & her children. Sexual jealousy, therefore, may have evolved as a solution to these problems. Men are more jealous of the sexual act; to avoid cuckoldry while women are more
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