Parental investment theory helps us to understand mate preferences. As a woman invests heavily in each child, she should seek a man with good genes to father her children, a man who shows commitment to remaining in the relationship and helping her raise offspring. If he also her material resources, her offspring will be more likely to survive. This helps to explain Buss’s cross-cultural finding that women valued material resources and industriousness in potential partners. In contrast, males who make less parental investment will be more reproductively successful if they have multiple matings with young, fertile women. This helps us understand why youth is universally important to men.
Trivers’ theory also explains why men are more likely to engage in short-term sexual relationships and women are more reluctant. As they require little investment of time and effort and have few costs, they can be seen as positive to men as they increase reproductive success. In contrast, females are less likely to be attracted to one-night stands as the men do not display a commitment to help raise the offspring which may result.
Trivers’ theory helps us to understand the observed differences in sexual jealousy. Men become distressed at sexual betrayal as it means that they may end up investing babies which are not theirs. In contrast, women are more distressed at emotional betrayal as this may lead their partner to move his support and investments to another woman, which may threaten the survival of the woman’s offspring.
Where trivers’ theory is weaker is in the relative rigidity of the behaviours is suggests. Parental investment theory ignores the obvious evidence that not all mating is about long-term relationships and that women, as well as men, clearly engage in short-term relationships, one night stands and affairs.
Trivers’ theory also tells us little about homosexual relationships which are non-reproductive. For example, it struggles to explain the reluctance of lesbians to engage in short-term, uncommitted sex when the risk of reproduction is not a threat. It also struggles to explain the preference for younger partners that is shown by older gay men. Tooby & Cosmides’ (1992) modular mind explanation argues that the same principles can be used to understand relationships and that age preferences shown are inbuilt in men, regardless of sexuality.
Sexual strategies theory was developed as an extension of Trivers’ theory by Buss and Schmitt (1993). It accepts the basic premise of parental investment that differences in parental investment between males and females lead to differences in mating behaviours. However, sexual strategies theory argues that mating is essentially ‘strategic’ and that humans have a complicated range of mating strategies – both short and long term – which are selected depending on the situation. What this means is that the range of possible reproductive behaviours is large and strategies are flexible. Rather than all women seeking commitment all of the time and all men seeking youth and sexual availability, sexual strategy theory argues that different strategies come into play depending on the situation. Sexual strategies theory differentiates between strategies that men and women might use when pursuing a short-term mate (e.g. a one night stand or date) and a long term partner:
According to sexual strategies theory, a short-term partner needs to be able to be identified as sexually available. For men, the most important qualities will be fertility (tied again to youth) and willingness to engage in activity without commitment. For women, a short-term fling can provide benefits, for example ‘mate insurance’ in case her proper mate disappears. It should involve a generous male as a miserly one is unlikely to provide resources later to possible offspring. He should also be physically attractive and provide good genes.
When selecting a long term partner, both sexes need to assess potential candidates for qualities related to resources and commitment. For men it is of crucial importance that the women they select will have good parenting skills otherwise offspring from that relationship may not survive. Even more important is faithfulness as they need to insure that any offspring they might invest in are biologically theirs. For women, it is important to identify a potential partner who will supple resources to offspring and will offer commitment and protection.
Sexual strategies theory argues that whilst we are ‘hard-wired’ to find certain characteristics desirable because they are advantageous in evolutionary terms, ‘socially based’ characteristics such as outgoing personality of shared interests are also desirable. People are seen as strategists, using their hand of playing cards to secure reproductive success.
This explanation also allows room for free will as everything is not seen to be biologically planned out and that we do have some say in who we choose to mate with and for what reasons, making this approach less deterministic. As well, the sexual strategies model is not as nature driven as the parental investment model as nurture is believed to be brought in with the desire of social characteristics in potential mates.
