The genetic explanations of aggression are arguably reductionist. The explanation focuses purely on one biological factor, genetics. In doing so it overlooks many other important factors, for instance deindividuation. Studies such as Mullen (1986) offer support that deindividuation can lead to aggression and therefore by not taking it into account, the genetic explanations are shown to be reductionist. Mullen analysed newspaper reports of 60 lynchings that had taken place in the first half of the 20th century. It was found the more people there were in the lynch mob, the more the deindividuation and the greater the savagery with which members of the crowd killed their victims. This therefore demonstrated support for the deindividuation theory of aggression. In addition, the twin study carried out by McGuffin and Gottessman
(1985) only found a concordance rate of 87% for aggressive and antisocial behaviour for MZ pairs. Considering MZ twins have identical genes, the concordance rate should have been 100% if genetics alone caused aggression. Therefore as the concordance rate was not 100% this indicates that there must be other factors involved, therefore making the genetic explanations of aggression reductionist as they fail to take these into account. Yet it could be argued that the genetic explanations of aggression are made slightly less reductionist due to the fact they acknowledge the influence of the neurotransmitters serotonin and dopamine and therefore don’t overlook neural mechanisms and their involvement in aggressive behaviour.
The genetic explanations of aggression are, as made obvious by the name, heavily nature based. The explanation focuses on aggression being genetic and it being passed down in families, which clearly makes it on the nature side of the nature vs. nurture debate. Studies such as Hutchings and Mednick (1973) demonstrate this further. Hutchings and Mednick (1973) reviewed over 14,000 adoptions in Denmark. They found a significant positive correlation between the number of convictions for criminal violence among the biological parents and the number of convictions for criminal violence among their adoptive sons. These findings are very compelling evidence that the genetic explanations are nature based as it was their biological parents that had an effect on whether they were aggressive or not as opposed to their adoptive parents who nurtured and raised them. However, Twin studies such Mcguffin and Gottesman could potentially demonstrate that the genetic explanations of aggression are slightly nurture based. Twins are arguably raised in the same way and exposed to similar things when growing up, especially MZ twins. This could therefore account for the concordance rates in this study both being so high, 87% MZ and 72% DZ. Aggressive behaviour could be learnt by both of the twins from the media or peers or alternatively aggressive behaviour by one twin could be mimicked by the other. Therefore this could demonstrate that the genetic explanations are partly nurture based, however for the large part, they are nature based.
The genetic explanation of aggression is arguably deterministic. It suggests that if a person has these ‘aggressive’ genes then they will inevitably be aggressive and that a person does not have the power to control it. Some legal experts have questioned the assumption that a violent offender can still exercise free will despite possessing a genetic predisposition to violent crime. For example in 2009 an Italian judge decided to reduce the prison sentence of a person convicted of murder because he was found to be the carrier of genetic variants thought to be associated with a predisposition to aggressiveness (Forzano et al 2010). This supports the idea that a person genetically predisposed to aggression cannot exercise free will as to whether they will be aggressive or not, making the genetic explanation of aggression deterministic. However, Hines and Malley-Morrison (2005) claim that the finding that aggressive behaviour might be genetically influenced simple means that some people, as a result of their genotype are more likely to commit aggressive acts than people without the genotype. Therefore instead of being deterministic, the genetic explanation could be probabilistic.