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| Could our ancestral roles still be influencing our behaviour? |
A recent psychological study has found that there are distinct differences in how male and female serial killers behave, and that these differences may be explained by considering the roles of our early human ancestors.
The Study
This study, conducted by psychologists Marissa Harrison, Susan Hughes, & Adam Gott, published in the journal ‘Evolutionary Behavioural Sciences’, is among the first scientific studies that directly compare the habits of serial killers based on their gender. The researchers used media sources (such as verified websites and local newspaper archives) to gather information about 55 male and 55 female American serial killers who committed their crimes between 1856 and 2009. The male and female serial killers were matched on their age and race to ensure that gender was the only factor responsible for their differences in killing habits.
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| Infamous serial killer, Ted Bundy |
Male serial killers were found to be almost 6 times more likely to kill a stranger, while female serial killers are much more likely to know, or even be related to, their victims. As such, male serial killers were most likely to choose victims outside of their hometown, whilst three-quarters of female serial killers killed victims from their birthplace. Additionally, 65% of male serial killers stalked their victims, compared to only 4% of female serial killers. You can see some of the other stark gender differences in the table below.
Proportion of Male Serial Killers
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Proportion of Female Serial Killers
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Killed for financial gain
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17%
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52%
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Killed for a sexual motive
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75%
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7%
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Victims were all children
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4%
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27%
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Killed spouse/partner
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11%
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27%
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Killed victims by poisoning
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8%
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47%
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Comparison of serial killers by sex from Harrison et al. (2019)
Marissa Harrison, one of the researchers who conducted the study, is an evolutionary psychologist and explains that the results support a ‘Hunter-Gatherer hypothesis’ of murder. For most of history, humans have followed the hunter-gatherer way of life, with the men travelling to hunt animals, and the women staying close to home, gathering nearby food and resources. It is this, the theory posits, that is responsible for the gender difference in killing habits: male serial killers stalk and “hunt” their victims (or “prey”), who are often strangers, in the same way that they hunted animals thousands of years ago, whilst women "gather" their victims, who are often people close to them.
What's Next?
Harrison et al.'s theory has far-reaching implications, as this research could prove useful in the real-world. For example, crime investigators can use this information to help track down killers i.e. if three murder victims are found to be related or in the same social circle, then perhaps their killer is a female member of that family or group. The finding may also help psychologists further understand why and how people commit murder, meaning they are in a better position to help prevent killings and rehabilitate violent offenders.
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| Aileen Wuornos |
Harrison et al.'s study has its limitations. Namely, only serial killers from the United States were analysed. Could the gender differences actually be due to gender roles in America, rather than evolutionary differences? If so, it is unlikely that the same results would be found in other cultures. Secondly, the study relied on acquiring their data solely from media reports, many of which may have presented a biased or sensationalised depiction of a serial killer’s behaviour. Finally, the hunter-gatherer theory itself may also have its flaws. Clearly, not all male serial killers stalk their victims, and not all female serial killers kill people that they know (for example, Aileen Wuornos, one of the most notorious female serial killers, murdered 7 men who were all strangers to her). This contradicts the theory, suggesting that there must be other factors affecting the habits of serial killers. Some psychologists, such as Jaime Confer, even argue that evolutionary psychological perspectives are speculative, as the theories are impossible to test.
In conclusion, I guess it is worth remembering that, in spite of Hollywood’s fascination with serial killers, serial murder is an exceptionally rare phenomenon. Consequently, cases are often unique and shocking, and the complex nature of the human mind means there is rarely a simply answer. For now, Harrison, Hughes, and Gott offer an interesting perspective on how our ancestral roles might continue to influence our behaviour.
References:
Confer, J. C., Easton, J. A., Fleischman, D. S., Goetz, C. D., Lewis, D. M., Perilloux, C., & Buss, D. M. (2010). Evolutionary psychology: Controversies, questions, prospects, and limitations. American Psychologist, 65(2), 110.
Harrison, M. A., Hughes, S. M., & Gott, A. J. (2019). Sex differences in serial killers. Evolutionary Behavioral Sciences.