Evolution and Human Aggression

Jealousy as an Explanation of Human Aggression
1. Sex Differences in Sexual Jealousy
  1. Males and females differ in the types of jealousy they are likely to feel and express.
    1. Males have low paternity confidence and so are likely to be jealous of sexual infidelity.
      1. If his mate had sex with another male he cannot be sure the offspring is his and carrying his genes.
    2. Females are more likely to be jealous of emotional infidelity.
      1. If her mate falls in love with another woman he is likely to leave her and her offspring.
        He would take his resources, making it hard to survive.
      2. Because of this she is likely to employ strategies to prevent her mate from leaving.
        Verbal aggression.
  2. A02 - Buss
    1. Found that men are significantly more likely to make threats of violence towards males who are perceived to have made sexual advances towards their mate.
    2. Women are more likely to use verbal aggression towards potential rivals.
      1. Often target the attractiveness and sexual conduct of the rival to try and reduce her attractiveness in the eyes of the male.
      2. Also has the adaptive advantage of no damage to the physical appearance, crucial if she is to retain and breed with the top males.
2. Cuckoldry and Sexual Jealousy
  1. Unlike women, men can never be completely sure they are the father of their child.
    1. Puts them at risk of cuckoldry.
      1. Cuckoldry = The investment of scarce resources into an offspring that is not your own, meaning the resources become unavailable to any existing children, and he is prevented from having any more.
  2. The male adaptive functions of sexual jealously, therefore, would be to deter the female from sexual infidelity, minimising the risk of cuckoldry.
    1. This may involve aggression (or the threat of), which if successful, would clearly be an adaptive function for the male.
3. Mate retention and Violence
  1. Buss suggested that males have a number of strategies evolved specifically for the purpose of keeping a mate.
    1. These include restricting their partners autonomy (direct guarding) coupled with negative inducements in the form of violence or the threat of violence.
      1. This aggression is adaptive for men as, not only does it reduce the exposure of their mate to other males, but it acts as a disincentive for them to be unfaithful as they will be fearful of the consequences.
  2. A02 - Dobash & Dobash
    1. Those who are perceived by their partner as threatening infidelity through their behavior (e.g. flirting) are more at risk of violence that those who are not.
      1. This can be supported by the numerous studies of 'battered women.'
        In majority of cases, extreme jealousy was cited as the reason for the violence.
Infidelity as an Explanation of Human Aggression
1. Sexual Coercion
  1. A consequence of men's suspicions of their partners infidelity is partner rape.
    1. Camilleri found that sexual assault of a female by her partner was directly linked to the perceived risk of her infidelity.
    2. Shields et al found that female victims of partner rape were more likely to have engaged in extra-marital sex than women who had not been raped.
    3. Camilleri et al found that men convicted of raping their wives were more likely to have experiences cuckoldry prior to the offence than men convicted of non-sexual partner abuse.
  2. Evolutionary theory would explain such extreme male aggression as adaptive because such behaviour dissuades the female from repeating her infidelity and also has the possibility of making her pregnant which would ensure she cannot become pregnant by another male.
2. Violence towards pregnant partners
  1. Sexual infidelity by a woman may sometimes lead to pregnancy.
    1. From the perspective of her LT mate, if the child is born, he risks cuckoldry.
      1. So, when a woman becomes pregnant with another mans child, the adaptive functions of aggression and violence towards the woman would be to terminate the pregnancy.
        Eliminating the rivals child and leaving her free to bear his child.
Evolutionary Explanations of Group Display - Warfare
1. Sexual Selection
  1. As there are relatively few women in societies compared to men, men have to compete for a mate.
    1. Displays of aggressiveness and bravery in battle are one way to ensure access to females as females find these characteristics attractive.
      1. As a result, a willingness to engage in warfare under such circumstances is adaptive as it enables young men to demonstrate that they possess desirable attributes that make acquisition far more likely.
  2. A02
    1. Leunissen & Van Vugt found that military men have more sex appeal than there non-military equivalents.
    2. Palmer and Tilley found that male street-gang members have more sexual partners than non-gang members.
2. Acquisition of status within the group
  1. Displays of aggression and ferocity by individual warriors in a group would lead to respect from peers in the group and would strengthen the bond between the brave males of the group.
    1. Any perception of cowardice would eradicate the respect held.
    2. High status within the group increases a males chance of being picked by a female and reduces competition from other men.
      1. As such, acquisition of status via bravery is another reason why engaging in warfare is adaptive.
3. Costly displays signal commitment
  1. One of the primary functions of ritual display, such as those associated with warfare, is to promote group solidarity.
    1. Since warfare is a particularly dangerous form of group display, those willing to engage in it have demonstrated a very clear commitment to the group, and often have physical scars to prove it.
      1. They have maximised their status within the wider group and have shown that they deserve to benefit from the profits of warfare.
        This has historically been sexual access to females.

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Evolution and Human Aggression

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