Biological Key Question

Features of Aggression

Aggression can be defined as hostile or violent behaviour towards others. Findings from Brendgen et al.'s (2005) twin studies have suggested that there is a strong genetic component to physical aggression, though social aggression may be due to environmental effects. This suggests that aggression could be due to both nature and nurture. It is also a behaviour that can be shown from a young age, so it could be inherited or learned early on in life (Brendgen et al., 2005; Bandura et al., 1961). While aggression may have been beneficial from an evolutionary stand-point, it can be a safety concern for society as it could lead to crime and death.

Summary: What are some of the features of aggression?

The Nature Argument

Other than Brendgen et al.'s (2005) twin study finding genetic links to aggression, other studies have identified gene variations linked to aggressive behaviour. The MAOA gene, also known as the warrior gene, is associated with aggression. McDermott et al. (2009) found people with a 'low expression' version of the gene react to provocation aggressively. Other research also find people with these gene have high levels of testosterone, a hormone linked to aggression.

The gene was first discovered in a large Dutch family with five generations of aggressive men. One of the women in the family sought help and revealed that of the men in her family, "one had tried to rape his sister; another had tried to run his boss down with a car; a third had forced his sisters to undress at knife point. Furthermore, the violent streak had a long history. In 1962, the woman’s granduncle had prepared a family tree that identified nine other males with the same disorder, tracing it as far back as 1870." Eventually, as more women approached scientists for help, the scientists were able to identify the MAOA gene which were found in the aggressive males of the family and some of the women who were carriers of the gene (Brunner, 1996).

In 2017, just three (3!!!) people were killed in shooting incidents in Japan. This number is miniscule in comparison to the nearly 40,000 gun related deaths in the United States of America. The difference in culture, gun laws and attitudes towards firearms could account for the large discrepancy, suggesting that the genetic explanation may not fully account for aggressive behaviour.

Summary: Describe two opposing explanations of aggression. What types of aggression are affected by each?

Application: What happened with the infamous 'Dutch Family' and the aggressive acts of men in that family? Why might there be such a big difference in gun related deaths in the US versus Japan?

While it may be near impossible to predict or control the environment children will grow up in, we can test with relative accuracy the genetic outcome for babies. Considering the advancements and research into identifying 'aggressive genes', perhaps babies could be screened for the MAOA gene so parents can decide if and how they wish to proceed with family planning.

Summary: How are parents and babies tested for genetic markers? Why would people want to do that?

Application: Which gene could be screened for aggression? Why might genetic screening for genetic markers of aggression be beneficial?

Conclusion

Based on what you've learned, how do you think society might change as we learn more about the biological causes of aggression? Is it ethical to screen for genetic markers of aggression? How might this affect society culturally with different beliefs about genetics and abortion?

References

Dutch family article

Prenatal testing