There have been many investigations on the linkage between genetics and aggression. Some work has been conducted with the monoamine oxidase A gene (MAOA) and behavioral aggression (McDermott et al., 2009). With many genetic experiments Drosophila melanogaster has been a reliable model in gaining understanding on genotype and phenotype correlations. It has been shown that the fru gene is critically involved in sex-specific patterns of aggression and forming dominance (Vrontou et al., 2006). Through fMRI studies of genetic variants, the serotonin pathway many be useful in understanding the coupling of genetics, brain physiology and aggressive behavior (Craig and Halton, 2009). Below will go into a little more detail of genomic influence on human behavior and the social implications.
Genomic Influences on Human Behavior
Human behavior is a complex system that is influenced by genomic, brain physiology and environmental cues. Due to this complexity it is hard to narrow the causal relationship between specific genes and human behavior. The hypothalamus, pituitary and adrenal axis affect stress levels. The serotonin pathway has been involved in aggressive behavior, as well as hypoglycemia in certain individuals (Craig and Halton, 2009). The evidence of specific genes that impact aggression is mixed. Androgen receptors associated with shorted CAG repeats seem to imply increased aggression in some populations (Rajender et al., 2008). MAOA gene has been linked to the aggressive behavior through oxidizing of serotonin, norepinephrine and epinephrine. When MAOA gene has variable number tandem repeats there seems to be an association to increased aggression (Craig and Halton, 2009).
There are several social implications of linking genetics and aggressive behavior. Firstly, it is the age-old debate on nature vs. nurture. Scientists tend to discredit the potential positive and negative feedback loops of socialization and how this affects aggressive behavior. Even though genetics have a major role to play in behavioral wiring, so does the socialization experience (Sapolsky, 2017). This observation from Sapolsky might help explain the mixed results in genetic research involving human behavior. Secondly, if there can be a reliable linkage between genetic defects and abnormal behavior in humans there might be social stereotyping of these affected individuals, which might produce a self-fulling prophecy. These affected individuals might feel they have no free will or control of their own destiny. This technocracy in the realm of genetics might lead to individuals guilty of a crime before a crime is committed. Thirdly, if genetic behavioral disease is predicted it might prevent employment in certain professions for these individuals, whereby further social stereotyping will result. Insurance companies might even raise rates for such individuals with genetic abnormalities, even though without clinical presentation. Another perspective is that society might force prophylactic psychiatric treatment without the consent of the patient. This is especially troubling in a free society with patients that are not showing clinical signs. The main point here is that just because there are linkages between genetic abnormalities and negative human behavior does not mean that there are no complex pathways which might mitigate the negative behavior.
Craig, I. W., & Halton, K. E. (2009). Genetics of human aggressive behavior. Human Genetics, 126, 101-113. doi: 10.1007/s00439-009-0695-9
McDermott, R., Tingley, D., Cowden, J., Frazzetto, G., & Johnson, D. D. P. (2009). Monoamine oxidase A gene (MAOA) predicts behavioral aggression following provocation. Proceedings of the National Academy of Sciences of the United States of America, 106(7), 2118-2123. http://www.pnas.org/cgi/doi/10.1073/pnas.0808376106
Rajender, S., Pand, G., Sharma, J. D., Gandhi, K. P. C., Singh, L., & Thangaraj, K. (2008). Reduced CAG repeats length in androgen receptor gene is associated with violent criminal behavior. International Journal of Legal Medicine, 122, 367-372.
Sapolsky, R. M. (2017). Behave: The biology of humans at our best and worst. New York, NY: Penguin Press.
Vrontou, E., Nilsen, S. P., Demir, E., Kravitz, E. A., & Dickson, B. J. (2006). Fruitless regulates aggression and dominance in Drosophila. Nature Neuroscience, 9(12), 1469-1471. doi:10.1038/nn1809