The ethological and evolutionary explanations for aggression
Ethology studies animal behaviour in their natural habitats. Lorenz believed animals have an innate mechanism for aggression that sees aggression levels building up until it is released as an aggressive act. This involves an innate releasing mechanism, an inborn device that prompts the release of aggression in response to a stimulus. This consists of the specific neural circuits hardwired into the brain which monitor the aggressive drive. Fixed action patterns involve the species-specific behaviours that are prompted by innate releasing mechanisms. Such behaviours occur as pre-set sequences to environmental stimuli. For instance, male sticklebacks will defend their nests by being prompted by the red bellies of other males to attack them. Evolutionary explanations of aggression see aggression as having being acted upon by natural selection to become more widespread in the population, as it has an adaptive survival value and increases reproductive fitness. Aggression in males helps them compete for females and resources. A common source of aggression here occurs through jealousy, where men fear the prospect of spending resources raising another man’s genes if his partner has been unfaithful. This leads to aggressively guarding females and aggressively punishing females suspected of infidelity, even to the point of uxoricide, wife killing.
Fig 15.2 Stags rutting is a way of displaying their attributes to potential mates
Tinbergen (1952) assessed the role of fixed action patterns upon aggression in male sticklebacks. Tinbergen had observed that male sticklebacks turn red during the breeding season, which seemed to elicit aggressive behaviours among male fish. Under laboratory conditions models of different coloured fish were placed in a tank containing a male stickleback, but he only attacked those models coloured red. Also, when a mirror was placed in his tank, the sight of his red coloured image caused him to attack the image. From his findings Tinbergen concluded that an external triggering mechanism, in the form of a male’s red belly, which is internally generated by hormone levels related to breeding behaviour, causes aggressive responses due to the presence of a fixed action pattern. Such behaviour is stereotyped, innate, universal to all members of a species, only used in one context and triggered by a specific stimulus.
• Sackett (1966) reared monkeys in isolation and provided them with pictures of monkeys playing, exploring and in threatening poses. As they matured they displayed reactions to the pictures of monkeys and threatening stimuli, suggesting that there is an innate mechanism to detect threat and then respond with aggressive behaviour.
• Daly & Wilson (1988) found that homicide rates are much higher when a man is about to be left, or has been left by his wife or partner, illustrating how the fear and jealousy involved in losing a partner can have aggressive consequences. This supports the evolutionary explanation that jealousy can lead to aggressive behaviour.
• Goetz et al. (2008) found that the main motivation for men’s violence against partners was to punish them for perceived infidelity and/or to deter them from being unfaithful. This supports the evolutionary explanation that aggression will be used to maximise reproductive success by ensuring a male has fathered his partner’s children.
Research into ethological explanations of aggression allowed aggressive behaviour to be studied in real-world scenarios, which gave insight into the biological nature of much of human aggressive behaviour.
There is a wealth of research evidence to support evolutionary explanations of aggression in both humans as well as animals. As such similar patterns of aggressive behaviour are seen in many species, including animals, it gives support to the idea that aggression has evolved as an adaptive device to maximise reproductive opportunities and to gain valuable resources.
A key point of the ethological theory is that behaviour will be universal to a species. This does not seem to be true for humans, as there are large individual differences in response to the same situation. For example, some men behave aggressively in response to perceived jealousy and infidelity, while others in ’open’ marriages would not mind.
There are cultural differences in murder rates of unfaithful wives. If such uxoricide brought evolutionary explanations, the rates would be consistent globally.
Much research support for ethological and evolutionary explanations comes from animal studies, presenting generalisation problems. It could be argued that humans have greater degrees of cognitive processing involved in aggressive behaviour that animals do not experience.
Teaching people who respond aggressively to jealousy that it is a naturally occurring phenomenon is a tactic used by relationship counsellors to help such people gain an understanding of their behaviour, with a view to them then being able to better control it.