In support of Weston C. McCool and Brian F. Codding’s article, U.S. homicide rates increase when resources are scarce and unequally distributed.

Identifying the factors that drive homicide rates is not only of paramount interest to scholars across the social and behavioral sciences but is necessary to inform policy decisions aimed at reducing lethal aggression. Studies nominate diverse causes of homicide, including ambient temperature, city greenness, firearm ownership, firearm laws, structural racism, income inequality, poverty, and more. However, without general theory scholars struggle to disentangle causal factors from correlated effects. This distinction is vitally important for designing interventions that target underlying causes rather than spurious correlations.

To work toward understanding the underlying causes of variation in homicide rates, our article in Evolutionary Human Sciences applies long-standing evolutionary anthropological theory (Daly and Wilson, 1988; Daly, 2016; Hackman and Hruschka, 2013) to evaluate the drivers of homicide rates across multiple decades in the United States (McCool and Codding 2023). We propose that when resources are scarce and unequally distributed, individuals with limited wealth and income may have incentives to undertake high-risk activities – including lethal violence – to access material and social capital. This body of theory also extends from our recent work, where we show that variation in global rates of generalized violence among subsistence-level societies can be explained by resource abundance and distribution, with violence peaking in areas with scare resources that are unevenly distributed across space (McCool et al., 2022).

In this article, we further evaluate this theory by systematically analyzing data from the FBI Uniform Crime Reporting (UCR) database on homicide rates, and the American Community Survey (ACS) on the proportion of households with income under the poverty level (proportion in poverty), and income inequality (Gini Index) across all 50 U.S. states for the years 1990, 2000, and 2005 to 2020. Importantly, our study is one of, if not the first to include the 2020 homicide and census data, which allows us to evaluate whether this general theory also partially accounts for the increase in violence during the COVID-19 pandemic.

Statistical results support the evolutionary anthropological hypothesis showing that while poverty and inequality are independently associated with an increase in lethal violence, a model that includes their interaction best explains variation in U.S. homicide rates. Model results show that from 1990 to 2020 predicted homicide rates peak in states where income is scarce and unevenly distributed. Results suggest that the increase in homicide rates during the height of the COVID-19 pandemic are driven in part by these same underlying causes that structure homicide rates across the U.S. over the last 30 years. Further, we suggest these results provide compelling evidence to expand strategies for reducing homicide rates by dismantling structures of systemic racism that generate and concentrate sustained poverty and economic inequality.

The perspective presented here can offer insight for addressing questions regarding the drivers of homicide, thus providing a foundation for developing science-based tools that may aid in violence mitigation both in the present and the future.

For more information, read the full article U.S. homicide rates increase when resources are scarce and unequally distributed.

References

Daly, M. (2016). Killing the competition: Economic inequality and homicide. Routledge.
Daly, M., Wilson, M. (1988). Homicide. Transaction Publishers.
Hackman, J., & Hruschka, D. (2013). Fast life histories, not pathogens, account for state-level variation in homicide, child maltreatment, and family ties in the US. Evolution and Human Behavior, 34, 118-124.
McCool, W. C., Vernon, K. B., Yaworsky, P. M., & Codding, B. F. (2022). Subsistence strategy mediates ecological drivers of human violence. PLoS One, 17, e0268257.
McCool, W. C. and B. F. Codding (2023). U.S. homicide rates increase when resources are scarce and unequally distributed. Evolutionary Human Sciences.

Bios:

Weston C. McCool is a Postdoctoral Fellow at the Society, Water, and Climate Interdisciplinary Research Group and the Anthropology Department at the University of Utah. His work utilizes population and evolutionary ecology to explore human behavioral adaptations to challenging socio-environmental conditions. His research spans multiple continents and leverages data from both the past and present to better understand the human condition. 

Brian F. Codding is Professor of Anthropology at the University of Utah. His work draws on ecological theory to explain variation in present and past human behavior, focusing on the dynamic interactions between individual decisions and local environmental contexts.