Genes and genetics are not thought to be the sole causes of aggression but may predispose us to act in an aggressive way when the correct environmental situations occur. Research suggests aggressive tendencies may be in part inherited. Many studies have been used to research this link including twin studies, adoption studies and studies into certain genes being associated with aggression. For example MAOA gene has been associated with higher levels of aggressive behaviour. This gene regulates serotonin, which lower levels of have been associated with aggression.
McGuffin et al found a concordance rate of 87% for aggressive behaviour among MZ twins supporting a genetic basis for aggression, as MZ had a high correlation than DZ twins. MZ twins share 100% of genes therefore this approach suggests they would show similar behaviour. However, DZ twins also has similarly high levels of aggression, a concordance rate of 72%. Methodological problems occur such as the sample size was small and restricted therefore limiting external validity and generalisations. Environmental factors may have influenced MZ concordance as they may have had more difficulty establishing an individual identity compared to DZ twins. Therefore they shared similar environmental influences causing them to have similar levels of aggression, suggesting how nature and nurture may work together in predisposing an individual to act aggressively. Therefore a combined biological and social approach may better explain tendencies for aggressive behaviour.
Additionally, in a replication of Bandura's bobo doll experiment researchers found no difference in MZ and DZ twins aggression towards the doll, after exposure to a model showing aggression. This suggests that aggressive behaviour is likely to be a product of environmental influences and learnt through social learning opposed to being caused by genetics or nature, therefore weakening the genetic argument and proving support for a role of nurture in development of aggressive behaviour.
Brunner et al found low levels of MAOA and a defective gene among members of a Dutch family prone to criminal behaviour supporting a genetic link to aggression. However, women from the same family who were found to have the same gene did not display as much aggressive behaviour as the men therefore suggesting that gender differences exist and interact with genes in predisposing an individual to aggressive behaviour. A methodological weakness of the study includes the use of self-report. This could have led to high levels of aggression being recorded than if an observation was conducted. Those within the Dutch family would have likely valued aggressive behaviour as the family had a history of criminal behaviour. They may have reported more acts due to social desirability. Therefore this reduces reliability and validity of results creating problems in drawing a conclusion to the actual role genetics plays in aggressive behaviour.
Both McGuffin and Brunner's studies suggest there may be a link between genetics and aggression. However such research highlights the complex relationship between genetic predispositions for aggression and the environmental factors which trigger it. Research shows that genes alone cannot offer an explanation and trying to isolate a cause for aggression within research is difficult. If a genetic predisposition can be identified this can have real world application in improving counselling, in order to reduce aggressive responses being provoked.
Explaining aggression through genes alone is reductionist. The role of cognitive, psychological and cultural factors are not considered. It is also deterministic to assume all behaviour is dictated through genetics. The theory does not consider the role of free will and conscious thought in decision making. Those who are found to have 'aggressive' genes are not always aggressive. Therefore causing social sensitivity in research as if 'aggressive' genes are identified this could lead to stigmatising and possible measures to control or limit aggressive tendencies. It may also lead towards genetic engineering to limit chance of someone being born with such genes which would be considered highly controversial. Although research evidence varies meaning a firm conclusion of the link between genes and genetics and aggression cannot be drawn.
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