Parents invest in an offspring to increases the chance that the offspring will survive at the expense of that parent’s ability to invest in any other offspring. Trivers’ theory states that males and females do not invest equally. A males investment is far more little than a females as males tend to produce many gametes and can potentially have unlimited amount of offspring. On the other hand female gametes are of little number and more costly to produce, for example she cannot produce another offspring whilst she is still pregnant. As a result females are choosier concerning mates. Males compete for quantity of females whereas females compete for quality of males and their resources.
As females invest a lot during both prenatal and post-natal pregnancy (feeding etc.) they aim to look for cues that men have resources for their offspring to survive (e.g. socio economic status). According to Buss (2003) females aim to choose mates who are able to provide resources, can physically protect her and the offspring and show good promise as a parent.
Males, on the other hand, have short term preferences. They prefer short term relationships in order to produce as many offspring as possible. Men seem to be less choosy and show decreased attraction following sex, which many believe is an evolutionary trait to prevent them from staying too long with one woman. Men generally look for cues that suggest fertility, such as a low waist to weight ratio and youth.
When males do invest parentally through resources, they are under pressure to protect themselves from the possibility of cuckoldry. Because males make a considerable investment in their children, they have greater concern than females about the fidelity of the mates. As a result they try to ensure their care is not misdirected to towards non relatives. This is supported by Daly and Wilson (1988) which show children under