The Effect of Publicized Life Sentences, Death Sentences, and Executions on Homicide

Steven Stack, Criminal Justice, Wayne State University

Research Grant, 1998

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The present study addressed several neglected issues in research on the death penalty and homicide:

Publicized Life Sentences vs. Executions. Research on the social control of homicide has focused almost exclusively on executions to the neglect of life sentences as a possible form of social control. The present study weighed the relative importance of publicized life sentences against publicized executions in the control of homicide. The results of a multiple regression analysis found no evidence of a reduction in homicide following a widely publicized life sentence story. In contrast, a widely publicized execution story was associated with a dip of 3.3 homicides for Whites (but not African Americans). Publicized executions, by providing severe enough punishment, may be preferable to life sentences in efforts to control lethal violence.

Publicized Executions: Abolitionist States. A second contribution was to test two alternative theoretical explanations for dips in homicide after a publicized execution. Publicized executions may reduce homicide through deterrence or through validation of societal norms against killing and their promotion of precautionary behavior (descriptions of the horrific crimes of offenders may remind persons that they are in danger, and some may avoid dangerous people for a while). The present paper contributes to the literature by exploring the impact of publicized executions in abolitionist states. A multivariate time series analysis determined that publicized executions were unrelated to homicide in abolitionist states. The results are consistent with the view that publicized executions may reduce homicide mainly through deterrence and not other processes from the theoretical literature.

Publicized executions, by providing severe enough punishment, may be preferable to life sentences in efforts to control lethal violence.

Critique of Previous Research. A third major contribution was to explain the many discrepancies in the findings on publicized executions and homicide. There have been considerable differences in the methodology used in these studies, which might help to explain their mixed findings. The present study analyzed 385 findings contained in twenty-five research studies published between 1935 and 2000. The results of a multiple logistic regression analysis determined that studies that assume execution stories will impact homicide rates for a period of more than thirty days were 95 percent less likely to report a homicide dip than studies assuming an effect period of thirty days or fewer. Studies based on the period after 1975, an era of declining celerity or speed of execution (swift punishments are a key assumption in deterrence theory), were 58 percet less likely to report a homicide drop than their counterparts. Studies based on analyses with an uncorrected problem of statistical multicollinearity were 97 percent less likely to report homicide dips than their counterparts. The model correctly predicted 91 percent of the 385 findings. It is suggested that researchers need to build a stronger consensus on methodological issues in order to reach a firmer conclusion on the impact of publicized executions on homicide.

Methodology. Homicide data were taken from the US Public Health Service’s annual Mortality Tapes. There were 164,199 homicides in this data set. Daily counts for each of the 2,922 days in the study period were obtained. Data on highly publicized life sentence and execution stories were taken from standard databases including the Vanderbilt Television News Archive, the New York Times Index, and Facts on File. A total of seventeen executions and fifteen life sentences met the criteria for being highly publicized stories. Controls are incorporated into the relevant statistical models for factors related to homicide and include holidays and temporal factors such as day of the week and season.

Bibliography

1. Stack, S. 2001. "Publicized Executions and the Incidence of Homicide: Methodological Sources of Contradictory Findings." In DuPont-Morales, Toni and Michael Hooper (eds), Handbook of Criminal Justice Administration, New York: Marcel Decker, pp. 355-369.

Blood and Soil: Modern Genocide, 1500–2000

Ben Kiernan, History, Yale University

Research Grant, 2002, 2003

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As the twentieth century closed, historians debated whether it should be labeled the “Century of Genocide” or whether mass slaughter of ethnic, national, or religious groups began much earlier, for instance during colonial expansion and domination of the New World. Resolution of this important question will answer key intellectual issues, including the nature of settler colonialism (whether it is inherently genocidal); the origins of twentieth century totalitarianism (which Hannah Arendt saw in the history of imperialism); the uniqueness of the Holocaust (which Steven T. Katz distinguishes from other historical genocides); the causes of mass slaughter (economic destabilization, poverty, and war, and more proximate causes, such as the seizure of power and decisions made by violent extremists); and, perhaps most important, the essential features and early warning symptoms of genocidal ideologies.

Racial discrimination is not always genocidal. Expansionism does not always produce mass slaughter. But their combination is explosive.

My book describes and analyzes genocide and its perpetrators’ ideological preoccupations in the period from 1492 to 2002. Genocidal ideology exhibits four major distinguishing features: racism, religious or antireligious prejudice, territorial expansionism, and the idealization of a specific social class. Targeting of racial and religious groups is specifically outlawed by the UN Genocide Convention, but the book shows that expansionism and, for instance, ideological preoccupations with cultivation are key factors when combined with such prejudices. Racial discrimination is not always genocidal. Expansionism does not always produce mass slaughter. But their combination is explosive. In pragmatic terms, expansionist ideology is more likely to provoke war, providing genocidists with legitimacy and cover essential to success. Idealization of the peasantry, and a preoccupation on the part of a range of perpetrators with specific forms of land use, combines with racialist and expansionist ideology to inspire hand-in-hand “purification” of both peoples and territories: genocide.

Genocide is the most serious and violent crime against humanity. My book links it with territorial aggression and with ideological notions of land use and class purity and superiority. Identifying the specific combination of such factors essential to genocidal policy and practice enables emerging human disasters resulting from dominance, aggression and violence to be detected in advance and hopefully, in a timely fashion, prevented.

Constitutional Design: Many Architects, No Buildings

Donald L. Horowitz, Political Science, Duke University

Research Grant, 1997, 1999

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This study concerns constitutional design for severely divided societies—the political institutions apt for peaceful coexistence or interethnic accommodation of groups with a history of antipathy that must nevertheless live together in the same state. There are two main constitutional prescriptions for such societies. One, consociational democracy, relies on an elaborate set of elite agreements and guarantees of proportional quotas and group vetoes, to prevent majority domination of the minority. The other, the incentives view, aims to institutionalize reasons for politicians to behave moderately and accommodate the interests of groups other than their own. Both prescriptions have their adherents, but neither can point to many cases of adoption of coherent packages of their recommended prescriptions, with accompanying benign effects.

The study funded by the Foundation centers on the issue of adoptability. In the face of various obstacles, can either prescription be adopted in a sufficiently strong dose to do what its proponents claim for it? The research design selects cases in which the usual obstacles to the adoption of coherent packages are missing because the choice of institutions has been given over to external actors not subject to the standard constraints: Fiji (a constitutional commission chaired by a foreigner), Northern Ireland (the U.K. and Irish governments), Indonesia (a small group of foreign-trained experts), Bosnia (representatives of the international community), and Cyprus (the U.N.).

So incoherence is not incompatible with ethnic conciliation, but serious attention to the coherent package problem is still by no means amiss.

The findings are that coherent adoptions are possible but highly unusual, even when conditions should be favorable for them. Northern Ireland’s Good Friday Agreement is a good example, but it was not configured by the two outside powers but by insiders in conditions so exceptional as to be sui generis. And its results thus far have been disappointing. In Fiji, Bosnia, and Indonesia, external dominance of the process did not last very long: insiders eventually took it over and negotiated compromises that had strong elements of incoherence to them. (In Cyprus, the U.N.’s consociational plan was rejected.)

In spite of the incoherent character of some of the constitutional packages adopted, benign results followed in certain cases. In Fiji, a multiethnic coalition won an election conducted under a conciliatory electoral system, despite the fact that its conciliatory features had been watered down. In Indonesia, a rather haphazard, incremental, multiyear constitutional process has produced what may turn out to be a durable democracy. But in Bosnia, international actors managed to select an electoral system that hurt the prospects of the most multiethnic Bosnian party. So incoherence is not incompatible with ethnic conciliation, but serious attention to the coherent package problem is still by no means amiss.

Bibliography

1. Horowitz, D. L. Constitutional Design: Proposals Versus Processes, in Andrew Reynolds, editor, The Architecture of Democracy: Constitutional Design, Conflict Management, and Democracy (Oxford University Press, 2002), pp. 15-36.

2. Horowitz, D. L. Domesticating Foreign Ideas in the Adoption of New Institutions: Evidence from Fiji and Indonesia, in John D. Montgomery and Nathan Glazer, editors, Sovereignty Under Challenge (New Brunswick: Transaction, 2002), pp. 197-220.

3. Horowitz, D. L. Explaining the Northern Ireland Agreement: The Sources of an Unlikely Constitutional Consensus, British Journal of Political Science, Vol. 32, no. 2 (April 2002), pp. 193-220.

Postcolonial Aspirations and Intimacies of Violence Among Gebusi of the Nomad Area, Papua New Guinea
and
The Role of Culture in the Early Evolution of Human Violence

Bruce M. Knauft, History, Emory University

Research Grant, 1993, 1998

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My HFG-supported research has included (1) analysis of information concerning homicide among the Gebusi—a rainforest people of Papua New Guinea who have had one of the highest rates of homicide yet documented; (2) comparative understanding of Gebusi violence in relation to simple human societies and in relation to human evolution more generally; and (3) field research concerning dramatic changes in the rate of Gebusi violence and killing in recent years.

The first dimension of my HFG-supported research considered the striking fact that though the Gebusi rate of killing was historically higher than that in Europe during World War II, this violence was seen as acceptable and appropriate. Gebusi killings typically took place after someone died of natural causes. In this circumstance, another Gebusi within the community was typically accused of having used sorcery to send lethal sickness. The person accused of sorcery was him- or herself considered to be a murderer. Frequently he or she was executed with the support of the general community, that is, in retribution for the life of the person they had allegedly killed by sending sickness. Despite the fact that few if any Gebusi actually attempted to practice sorcery in fact, the belief that they did led to a very high rate of killing. Most of these killings were of older persons and/or those perceived as irritable and antagonistic to others in the community. Because the size of communities was small, however, the killing of one or more members over the course of several years was not perceived by Gebusi to be a particularly great problem even though, statistically, this resulted in an extraordinarily high rate of homicide when figured on a per capita basis per annum.

Cases of sorcery were seldom avenged or were brought to the police by Gebusi themselves for conflict resolution; traditional patterns of sorcery inquest and divination were largely defunct.

The second dimension of my HFG research viewed patterns of Gebusi killing comparatively against those in other simple societies. Simple human societies often have a statistically high rate of killing though these deaths are often individualistic and infrequently constitute collective armed conflict such as warfare. The general tenor of social life in many such simple societies is one of friendly harmony most of the time despite occasional killings that may actually be quite high when calculated as a homicide rate per capita per year. This helps explain the apparent paradox by which the simplest human societies observed by researchers have often seemed socially harmonious despite the fact that they may have a statistical rate of killing comparable to that of more complex societies that practice frequent or virulent warfare.

The third dimension of my HFG-funded research considered dramatic changes in Gebusi homicide and violence between the early 1980s and the late 1990s. By the latter period, most Gebusi in my communities of study had been converted to Christianity, participated in market activity, and lived near the local government station and its airstrip. Beliefs in sorcery were now part of a Christian cosmology in which God was deemed responsible for taking action against evil persons such as sorcerers. Cases of sorcery were seldom avenged or were brought to the police by Gebusi themselves for conflict resolution; traditional patterns of sorcery inquest and divination were largely defunct.

Correspondingly, the homicide rate had dropped precipitously—to virtually zero during the 1990s. This dramatic change illustrates how changes in cultural norms, values, and social conditions can have a powerful impact on the rate of human violence. This finding lends credence to the notion that human violence is a solvable problem and is not an intrinsic or preordained feature of humanity.

Characteristics and Determinants of Global Homicide Crime Waves, 1946 to 1998

Gary LaFree, Sociology, University of New Mexico

Research Grant, 1999

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Difficulties in comparing political and legal systems have long hampered our efforts to estimate cross-national violent crime rates. Adding the requirement that such studies examine trends over time makes the task even more complex. In this research project, we used World Health Organization records to collect the most comprehensive set of annual homicide victimization data that has ever been assembled. In the main part of our analysis, it was possible to examine annual data for some forty nations for a fifty-year time period. This unique data base has provided answers to a variety of questions about trends in homicide across nations.

First, we were able to use these data to determine how common violent crime “booms” and “busts” have been since World War II. We defined crime booms as crime rates that increase rapidly and exhibit a positive sustained change in direction. Based on our definition, we found that twelve of the nations in our sample of thirty-four nations (or 35.5 percent) had experienced crime booms since World War II. These findings contradict both those who argue that booms in violent crime have been rare or nonexistent in the postwar period and also those that argue that violent crime booms have been nearly universal. In support of modernization perspectives, we also found that 70 percent of the industrializing nations in our sample qualified as having crime booms, but less than 21 percent of industrialized nations did.

Our results provide little support for the argument that there has been a growing rift in homicide rates between industrializing and highly industrialized nations. However, we also find that convergence in national homicide rates is far from universal.

Second, we were also able to use the data to examine whether violent crime rates for the nations of the world are getting more similar or less similar over time. Some researchers have argued that crime rates for all nations of the world will gradually converge as individual nations go through similar globalization processes while others contend that instead there will be growing divergence between crime rates in industrializing nations and the industrial elite but convergence in crime rates within both groups. We use econometric methods to test for convergence and divergence in homicide victimization rates for thirty-five nations from 1956 to 1998. Our results provide little support for the argument that there has been a growing rift in homicide rates between industrializing and highly industrialized nations. However, we also find that convergence in national homicide rates is far from universal. In fact, nearly all of the cases of homicide convergence we could identify took place among nations of the European Union. Thus, it appears that modern examples of crime convergence are limited mostly to nations that are geographically and culturally proximate. A paper reporting these results is currently under review.

And finally, we are in the process of using the global homicide database to examine a series of related questions: Is there evidence that male and female rates of homicide victimization are getting more similar over time? How has the global transition to democracy affected homicide victimization rates? And do nations with higher levels of social capital experience lower rates of homicide victimization?

Bibliography

1. 2002. Declining Violent Crime Rates in the 1990s: Predicting Crime Booms and Busts. Criminology 25:145-168.

Nationalism and Violence in Two Post-Soviet Republics: Azerbaijan and Moldova

David D. Laitin, Political Science, University of Chicago

Research Grant, 1997, 1998

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The goal of my HFG grant was to account for variation in the degree of violence in the critical moment of state breakdown in the former Soviet Union. At this moment, as in the case of many imperial breakdowns, the level of ethnic violence increased markedly compared to the era of Soviet hegemony. My previous research examining ethnic identification in four republics (Estonia, Latvia, Ukraine, and Kazakhstan) was inadequate to account for variations in violence, since all of them were peaceful. The HFG grant allowed me to replicate the research techniques used in my earlier studies to include two cases where there was significant secessionist violence in the new republics (Moldova and Azerbaijan). Two theories were tested to account for the variation in cases. The oft-cited theory of Donald Horowitz emphasizes psychological mechanisms affecting self-esteem; the greater the challenge to ethnic self-esteem, the more likely the violence. An alternative theory by James Fearon and Pieter van Houten, based on Rogers Brubaker’s “triadic configuration,” is also tested. This theory relies on a commitment logic, and hypothesizes secessionist violence where minority groups get clear signals of support, should they try to secede, from a national homeland.

These findings are important because they tell us that the quality of ethnic relations is less important than previously thought in accounting for violence; and that interventions by neighboring states (or rump groups within them) are often the culprits for civil war violence.

The newly collected data did not support the predictions that would follow from Horowitz’s theory. Ethnic relations in Moldova and Azerbaijan were no more challenging to self-esteem than in the peaceful republics. The commitment theory, however, was consistent with the data and the historical record. In Moldova a rump-Soviet army unit and in Azerbaijan a strong militia from Armenia gave unqualified support to secessionists, thereby emboldening them. Meanwhile, Russia gave only mixed signals to the Russian minorities in the four peaceful republics. These findings are important because they tell us that the quality of ethnic relations is less important than previously thought in accounting for violence; and that interventions by neighboring states (or rump groups within them) are often the culprits for civil war violence. The research findings were published in Comparative Political Studies (Laitin 2001) as “Secessionist Rebellion in the Former Soviet Union.” The research materials were also the basis for a doctoral dissertation by Alena Guboglo at Moscow State University.

A Military History of East Africa in the Nineteenth Century

John Lamphear, History, University of Texas

Research Grant, 2002, 2001

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The Harry Frank Guggenheim Foundation made possible archival research in the U.K., France, Kenya, Tanzania, and Zanzibar, and field research in Uganda, to collect data for the first macrocosmic history of traditional organized violence in East Africa, as well as the analysis and organization of that data in anticipation of writing the manuscript itself. The goal has been to explore the historical evolution of the military systems of a wide range of East African societies from about the 1770s to the 1890s, and, in the process, to propose a major modification of the prevailing notion of a “pacified” African past, as well as to suggest historical continuity between precolonial conflict and contemporary “ragged warfare.”

The findings so far certainly support the contention that, far from being inherently limited, traditional warfare in the region was as common and lethal as in any other part of the world. Nevertheless, much of the conflict took the form of what I am now terming “raiding war” (in some ways roughly equivalent to what used to be termed “primitive war”), as opposed to what I call “campaigning war,” i.e., the “conventional” warfare—involving standing armies, protracted campaigns, and set-piece battles—far more familiar to Western experience and scholarship.

The findings so far certainly support the contention that, far from being inherently limited, traditional warfare in the region was as common and lethal as in any other part of the world.

The data gathered far surpassed expectations in terms of its sheer quantity. Moreover, it is revealing a much more complex and nuanced picture of precolonial East African military history than anticipated. There are, for example, a surprising number of discernible instances of societies making a transition from raiding war to campaigning war during the nineteenth century. Some of these transformations clearly involved external factors, such as imported weaponry (and a special emerging subtheme is the impact of the early East African firearms trade), long-distance commerce, and imperialism. Nonetheless, internal factors, such as modifications to age-class structures and the centralization of politico-religious leadership, were plainly crucial as well.

One of the most difficult aspects of the work to date has been systematically to establish the actual correlation between precolonial warfare and contemporary violence. While certainly empirical evidence shows clear continuity, there obviously also have been extreme distortions of earlier practices, making it hard to suggest specific ways that strategies for the restoration of peace in areas such as northern Uganda and Rwanda might best utilize lessons from the earlier historical experience.

A chapter, “Sub-Saharan African Warfare,” in Jeremy Black (ed.), War in the Modern World since 1815 (Warfare and History) (London: Routledge, 2003), was directly based on my Guggenheim-supported research. In addition, a conference paper on the military background to the Maji Maji Rebellion, and three articles for journals that are nearing completion likewise draw on that research. Finally, much of the data is being incorporated into my teaching; important components of a graduate seminar in East African history offered last semester, for instance, were directly inspired by the work the Guggenheim Foundation has supported.

Determinants of Infant Abuse and Neglect In Group-Living Macaques

Dario Maestripieri, Psychology, Emory University

Research Grant, 1997, 1998

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Infant abuse and neglect is not a phenomenon unique to the human species.

In monkeys and apes, some mothers occasionally display violent behavior towards their infants and a few others abandon their infants shortly after birth. In macaque monkeys, infant abuse generally occurs in the first two to three months of infant life. Abusive mothers typically drag their infants on the ground or push, hit, or throw them around. Abusive mothers typically alternate short bouts of abuse with long periods of appropriate care-giving behavior. The consequences of abuse may range from infant distress to serious injury and death.

This project had three main goals: 1) to investigate the occurrence of infant abuse and neglect in two large populations of macaques living at the Field Station of the Yerkes National Primate Research Center in Georgia over a period of thirty to thirty-five years; 2) to observe and study the behavior of macaque mothers who physically abuse their infants; and 3) to investigate possible physiological differences between macaque mothers who abuse their infants and nonabusive mothers.

Information for the first study was obtained from the Animal Records of the Yerkes Primate Center. Data were available for about four hundred pigtail macaques and over three thousand rhesus macaques over a period of five to seven generations.

Behavioral observations of abusive mothers in rhesus and pigtail macaques revealed that these individuals do not show any gross behavioral abnormalities in their social interactions with other group members.

Data analyses showed that in these two populations, 5–10 percent of all infants born every year are physically abused by their mothers and 1–3 percent of them are abandoned shortly after birth. Infant abuse, but not neglect, was concentrated in some families and among closely related individuals such as mothers and daughters, or sisters. Thus, abuse appears to be transmitted across generations along the maternal line, and macaque females that are abused as infants are likely to become abusive mothers themselves. Neglectful mothers were young females who abandoned only one of their offspring, typically the first, whereas most abusive mothers repeated abuse with successive offspring. Moreover, abusive mothers were very consistent in their rates and physical patterns of abuse over time and across infants.

Behavioral observations of abusive mothers in rhesus and pigtail macaques revealed that these individuals do not show any gross behavioral abnormalities in their social interactions with other group members. However, they can be differentiated from other mothers for their controlling parenting styles, as they score higher than controls on measures of maternal protectiveness and rejection. For example, they both restrict their infants’ movements and reject their attempts to make contact more frequently than nonabusive mothers. In pigtail macaques, abuse was often preceded by stressful social events such as aggression within the group or infant kidnapping. Since abusive mothers are not more likely to find themselves in such stressful situations than other mothers, this suggests that abusive mothers are individuals that are particularly vulnerable to stress or with problems in emotion regulation.

The third study found that rhesus macaque abusive mothers did not differ from controls in their profiles of estrogen and progesterone during late pregnancy and early lactation. Since these hormones are involved in the regulation of maternal responsiveness, it does not appear that abusive behavior is the result of a deficit in maternal motivation. Some differences between abusive and nonabusive mothers, however, were found in the activity of physiological systems that regulate responses to stress. This is consistent with the hypothesis that abusive mothers have problems with emotion regulation and raises the possibility that these alterations in responsiveness to stress may be the result of an early trauma, i.e. abuse experienced during infancy.

Bibliography

1. Maestripieri, D. Wallen, K. & Carroll, K. A. Infant abuse runs in families of group-living pigtail macaques. Child Abuse & Neglect, 21: 465-471, 1997.

2. Maestripieri, D. Parenting styles of abusive mothers in group-living rhesus macaques. Animal Behaviour, 55: 1-11, 1998.

3. Maestripieri, D. & Carroll. K. A. Risk factors for infant abuse and neglect in rhesus monkeys. Psychological Science, 9: 143-145, 1998.

4. Maestripieri, D. Megna, N.L. Hormones and behavior in abusive and nonabusive rhesus macaque mothers. 2: Mother-infant interactions. Physiology & Behavior, 71: 43-49, 2000.

Latino Violence in the United States: A Five-City Study

Ramiro Martinez, Criminology, University of Delaware

Research Grant, 1999

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The HFG grant supported the first book-length attempt to answer questions on Latino homicide with hard evidence and empirical research that helps us better understand the impact of the latest wave of Latino immigration. My focus is on Latinos and Latino homicide in five cities—Chicago, El Paso, Houston, Miami, and San Diego—which have faced extensive and sustained waves of immigration, and in the case of El Paso and San Diego, some of the longest history of Latino settlement in the United States. This process, in turn, should impact Latinos more than any other ethnic group and have a corresponding influence on homicide. But the alleged immigration/crime link has had relatively little direct influence on Latinos. Latino homicide rates have not changed in a uniform manner. Instead, they have been characterized by exceptional variation across urban areas since 1980: some rose, others fell or even remained stable, but most remained lower than expected.

More specifically, my primary objectives were: 1) to describe and explain the extent of urban Latino homicide and relate the patterns that emerge to other ethnic group patterns; 2) to explore similarities and differences within the Latino population; and 3) to determine the influences and circumstances that shape the nature of Latino homicides in urban communities. With the population growth of Latinos—soon to be the largest ethnic minority group in the U.S.—writers and researchers have promoted a discussion about urban violence that rests on beliefs, guesses, and opinions about the latest threat to the national social fabric. This book challenges the perceived nature of Latino criminality and the assumption that Latinos, especially young Latino males, are a criminally inclined or a highly victimized ethnic group, by filling the gaps in contemporary analyses of Latino violence.

Latino homicide rates have not changed in a uniform manner. Instead, they have been characterized by exceptional variation across urban areas since 1980: some rose, others fell or even remained stable, but most remained lower than expected.

In closing, by focusing on Latinos and homicide in these five cities, the conclusions presented in this book demonstrated that Latinos are not usually engaged in high levels of violent crime and that immigration can be a positive influence on communities that suppresses crime. Until now, this group has largely gone ignored and this notion has rarely been explored. But the incorporation of Latinos into criminological research will inevitably intensify, and when it does, my hope is that this book will provide a foundation on which others can build studies that effectively capture meaningful group differences, as well as a rationale for moving beyond Black and White comparisons. Since the United States increasingly resembles its multiethnic cities, and since Latino-majority communities are proliferating, the time has come to ask more questions about Latinos and crime.

Bibliography

1. Martinez, Ramiro Jr. Latino Homicide: Immigration, Violence, and Community. New York City and London: Routledge Press. Taylor & Francis Group.

2. Martinez, Ramiro Jr., Amie L. Nielsen and Matthew T. Lee. Reconsidering the Marielito Legacy: Race/Ethnicity, Nativity and Homicide Motives. (Social Science Quarterly, June 2003.)

Molecular Genetics of Aggressive Behavior in Drosophila Melanogaster

Charalambos P. Kyriacou, Genetics, University of Leicester

Research Grant, 2002

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Aggressive behavior has been extensively studied, both in vertebrate and nonvertebrate model organisms. Remarkably, these studies indicate common elements that underlie socially mediated changes in behavior. For example, chemical messengers such as serotonin have been implicated in aggression in mammals and crabs. It is rather surprising then, that the fruit fly, Drosophila, has not been used to explore the molecular genetics of aggression, despite the fact that this type of behavior has been documented in flies. We have been attempting to find out which genes and proteins get “turned on” in flies when they behave aggressively to each other.

We can then take these candidate aggressive genes and, using various techniques, express them at high levels in a fly to see if it becomes more aggressive.

As most of the aggressive interactions in fruit flies occur during defense of a resource such as food, territory, or a mate, we have studied male-male aggressive encounters on a patch of food. We have found that fruit fly males can be extremely aggressive with each other, or, at the other extreme, barely notice each other at all. As these flies are genetically identical, we can ask the question, “which genes have been turned on in the very aggressive flies, compared to those that are more ‘mellow’ and nonaggressive?.” To answer this question, we have made use of a relatively new technology called microarray analysis, which allows us to study the expression of all of the fly’s thirteen thousand genes at once. Thus we take very aggressive and very “mellow” flies, mash up their heads, extract the working copy of every one of their genes, the RNA, and, using the microarray, measure which genes show relatively high or low levels of RNA in the two types of animals. In this way we obtain a gene profile of the aggressive and the nonaggressive flies. We can then take these candidate aggressive genes and, using various techniques, express them at high levels in a fly to see if it becomes more aggressive. We can even modify this procedure and overexpress these candidate “aggro” genes in specific regions of the brain, thereby mapping brain structures with behavior. Because it appears that vertebrates and insects may share many of the genetic elements for aggression, our findings with the fruit fly model shall be of fundamental interest to those working on human aggression.