Risk, Uncertainty, and Violence in Eastern Africa

A Regional Comparison


Previous research on warfare in a worldwide sample of societies by Ember and Ember (Journal of Conflict Resolution, 36, 242–262, 1992a) found a strong relationship between resource unpredictability (particularly food scarcity caused by natural disasters) in nonstate, nonpacified societies and overall warfare frequency. Focusing on eastern Africa, a region frequently plagued with subsistence uncertainty as well as violence, this paper explores the relationships between resource problems, including resource unpredictability, chronic scarcity, and warfare frequencies. It also examines whether resource scarcity predicts more resource-taking in land, movable property, and people, as well as the commission of atrocities. Results support previous worldwide results regarding the relationship between resource unpredictability and warfare frequency. Results regarding resource-taking and atrocities are more nuanced and complex. In almost all findings, relationships are generally in opposite directions in nonstate and state societies. In post-hoc analyses, atrocities are significantly more likely to be committed in states than in nonstates.

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  1. 1.

    The expectation that droughts would predict more violence has long been held among humanitarian organizations and climate change advocates (e.g., UN OCHA/Kenya 2010; Smith 2009).

  2. 2.

    Durham (1976:391) was more specific, suggesting that scarcity and fighting over resources produce fitness benefits only when resources are dependable and of high quality and only if at least some of the aggressors obtain resources as a result of war. In a similar vein, Manson and Wrangham (1991:374) argued that fighting for material resources is likely when they are of sufficient value and alienable.

  3. 3.

    We note that resource competition is not necessarily the same thing as resource scarcity. For instance, Manson and Wrangham (1991) and Wrangham and Glowacki (2012) suggest that chimpanzees and humans in simpler societies take resources opportunistically when they have an asymmetrical advantage. However, Wrangham (1999) noted that chimpanzee attacks were more frequent where competition is intensified by longer dry seasons.

  4. 4.

    The likelihood of a group winning and hanging on to resources taken may depend heavily on the evolution of cooperative group behavior; see Bowles 2008, 2009.

  5. 5.

    Kelly (2005) points to the potential loss of territory because of the need to avoid border regions when clear dominance is not possible.

  6. 6.

    Not all studies have shown this linkage—for example, Witsenburg and Adano (2009) reported for Marsabit District that wet years and wet months were more likely to exhibit the most casualties during livestock raids.

  7. 7.

    However, Letendre et al. (2010):682) suggest that resource deprivation in state societies will be positively associated with internal war.

  8. 8.

    Tooby and Cosmides (2010) suggest that humans are evolved to have a special emotional rage for combat, which, if so, could explain atrocities, but we don’t see how this would explain variation.

  9. 9.

    The first author has used her personal data file, which is available from the author upon request. These data were later published in World Cultures in somewhat different form.

  10. 10.

    We used random elimination where we could. In a few instances, we chose to eliminate the society that caused the least number of lost cases.

  11. 11.

    Some authors, such as Otterbein and Otterbein (1965), Ericksen and Horton (1992), and Fry (2007), have advocated keeping feuding and warfare separate.

  12. 12.

    Because the number of state societies is quite small, we did not remove neighbors. Note that such removal did not make much difference for nonstates.


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The comparative research in eastern Africa was supported by the Office of Naval Research ONR under MURI grant no. N00014-08-1-0921 to George Mason University with a subaward to the Human Relations Area Files (PI: Claudio Cioffi-Revilla; co-PIs: Carol R. Ember, Sean Luke, and Kenneth De Jong). The opinions, findings, and results are those of the investigators and do not reflect the views of the sponsors. The earlier work on warfare was supported by the program in cultural anthropology at the National Science Foundation (BNS-8211024 and 8606337) in grants to Hunter College, CUNY (PIs: Carol R. Ember and Melvin Ember). A presentation of the major results was given by Carol Ember at the 2010 annual meeting of the American Anthropological Association (New Orleans) in the organized session “Circulation, Exchange, and Redistribution of Resources, People, and Power: Relationship to Risk and Security.” The session was sponsored jointly by the Society for Anthropological Sciences and the Evolutionary Anthropology Society. A similar presentation was made at the 2011 annual meeting of the Society for Cross-Cultural Research (Charleston, SC) in the organized session “A Tribute to Herbert Barry” (Alice Schlegel, organizer).

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Correspondence to Carol R. Ember.

Appendix: Sample Cases (Table 10) and Coding Definitions

Appendix: Sample Cases (Table 10) and Coding Definitions

Table 10 Cases in eastern African sample

Frequency of Warfare

For ratings of warfare frequency in societies represented in the HRAF Collection of Ethnography, the coders were asked to read the full-text information in categories 578, 628, 648, 721, 723, and 726 of the Outline of Cultural Materials (OCM), the HRAF subject-indexing system.

All frequency ratings were based on a five-point ordinal scale used by each of the two coders: (1) Warfare seems to be absent or rare (coders were instructed not to code warfare as absent simply because there is no information, unless the ethnographer explicitly states that there is little or no warfare, or unless the ethnographer describes intercommunity and intra- and inter-societal contacts but does not mention hostilities); (2) Warfare seems to occur once every 3 to 10 years; (3) Warfare seems to occur at least once every 2 years; (4) Warfare seems to occur every year, but usually only during a particular season; (5) Warfare seems to occur almost constantly and at any time of the year.

Definitions of warfare, internal and external, are provided in the Methods section. Substitute “internal warfare,” “external warfare,” “warfare in which the focal society attacks other societies” “warfare in which the focal society is attacked by other societies” to replace the word “warfare” in the 5-point scale above. The latter two are referred to as “external attacking” and “external attacked,” respectively, in the paper. Each of the five warfare frequency scales is summed across the two coders for a scale that is minimally 2 and maximally 10 in the analyses reported here. Missing values indicate that one or both coders did not find enough information or found it confusing.


In the HRAF Collection of Ethnography information on pacification was generally contained in OCM categories 177 and 636. For this study, only societies rated 1 or 2 were used: (1) Not pacified for all or part of the 25-year time period as reported by ethnographer; (2) Inferred to be unpacified because warfare frequency is greater than or equal to 3 by individual coder. For the remainder of the scale see Ember and Ember (1992b).

Outcomes of Warfare in Terms of Resource Acquisition

The following scales are used for rating internal warfare and external warfare separately. With external warfare the point of reference is what the focal society is doing during warfare, not what the external society is doing to them.

In the HRAF Collection of Ethnography, most of the information for these ratings came from categories 726 and 728.

Taking of Land Resources

(1) the defeated are never driven from their territory; (2) the defeated are sometimes driven from their territory, but the victorious rarely use the land of the defeated; (3) the defeated are sometimes driven from their territory and the victorious sometimes use the land of the defeated; (4) the defeated are usually driven from their territory and the victorious sometimes use the land of the defeated; (5) the defeated are usually driven from their territory and the victorious usually use the land of the defeated; (7) not applicable because warfare does not occur during time period; (8) don’t know; (9) confusing or contradictory.

Taking of Movable Property and Taking of People

The following scale is used with both the phrases “non-land resources and non-people resources (e.g., animals, food, tools, transport)” and “people”: (1) are never taken from the defeated; (2) are sometimes taken from the defeated; (3) are usually taken from the defeated; (4) are always taken from the defeated; (7) not applicable because warfare does not occur during time period; (8) don’t know; (9) confusing or contradictory.

Behavior Toward Combatants and Noncombatants

The point of reference is what the focal group does to the other side when engaged in armed combat. If there is a specific community or district focus, this focus may be used for behaviors in internal warfare. For external warfare the focus is the named society, not how other societies behave when attacking the focal society.

Killing or Attempting to Kill Noncombatants

(1) Noncombatants are never or rarely attacked with the intent to kill; (2) Noncombatants are sometimes attacked with the intent to kill; (3) Noncombatants are usually attacked with the intent to kill; (4) Noncombatants are always attacked with the intent to kill; (7) not applicable because warfare does not occur during time period; (8) don’t know; (9) confusing or contradictory.

The following behaviors are rated with essentially the same scale (1–4, 7–9). Replace the phrase marked XX with “never or rarely” for a score of 1, “sometimes” for a score of 2, “usually” for a score of 3, and “always” for a score of 4.

Rape of Women Associated with Armed Combat

“Women are XX raped.”

Torture or Mutilation of Noncombatants and/or Combatants

“Torture or mutilation is XX practiced.” Coders were asked to separate killing itself from deliberate attempts to promote or prolong physical and/or psychological pain and suffering.

Destruction of Resources (e.g., crops destroyed, houses burnt)

“Resources are XX destroyed.”

Nonphysical Intimidation of Noncombatants

“Intimidation of civilians is XX.”

Military Glory

This rating follows Philip Slater’s (1964:6–7) code for Pursuit of Military Glory. The three-point scale is: (1) low (war is viewed as abhorrent, military virtues are not valued, or saving’s one life is considered appropriate); (2) moderate (defensive virtues are valued in war—military resistance, endurance, fortitude; values other than military predominate although military values are important; contests of bravery, skill, or endurance are important parts of masculine relationships; raids are frequent but conducted primarily for economic reasons); (3) high (warriors seek death in battle or view it preferable to defeat; being a warrior is viewed as the principal road to earthly or other-worldly glory; war is considered glorious, the primary source of status and prestige; war is waged for obtaining rank, honor, or fame; military virtues, such as valor, recklessness, and fighting skill, are the most important in the society; military trophies are the principal source of rank and prestige).

Killing of Combatants

This three-point scale ranged from (1) low (attacks are aimed at one or a few individuals, or a few individuals are killed out of a large group) to (2) moderate (a considerable number of enemies are killed in the course of particular battles) to (3) high (try to kill most of the enemy combatants in battle); (7) not applicable because warfare does not occur during time period; (8) don’t know; (9) confusing or contradictory.

Resource Problems

The two measures of unpredictable resource problems were “threat of famine” and “threat of natural (weather and pest) disasters.” Famine is a time of starvation when either many human deaths occur or it is reported that a substantial portion of the society has to move because of a lack of food. [Note: ordinary seasonal migration is not counted, nor is chronic hunger.] The famine scale is shown below. For threat of natural disasters the coders were asked to rate the incidence of severe weather or pest problems that seriously destroyed food resources. Coders using the HRAF Collection of Ethnography were asked to look for information in 730 (particularly 731 and 735), 132, 133, and 312.

Threat of Famine

(1) low threat of famine—food is reported to be ample or adequate, with no report of famine; or famine occurred only in the past (not in the 25-year time period); or occasional periods of food shortage are reported, but the scarce foods are reported to be replaced by other available foods; or there may be chronic hunger in the absence of the conditions included in the following scores (2–4); (2) moderate threat of famine—there is no reported famine during this period, but the ethnographer states there is an ever-present threat of famine; (3) moderately high threat of famine—one famine occurred during the 25-year time period; (4) high—more than one famine occurred during the 25-year time period; (8) don’t know.

Threat of Natural Disasters

The same scale is used as for threat of famine (above) replacing the word “famine” with “severe natural disrupters of food supply.”

Chronic Resource Problems

In contradistinction to unpredictable resource problems, there might be chronic or predictable problems. Coders were told that early ethnographers sometimes suggested that hunter-gatherers or other mobile groups lived precariously because they constantly had to move in search of food. This was not to be taken as chronic hunger as long as other foods were usually obtained within a day or so. Coders were asked to look for information in OCM categories 146 and 261–262. We originally rated chronic resource problems as the Embers (1992b) did: (1) low or rare—food is reported to be adequate or abundant for the population with no report of the following problems; (2) there are “hungry times” during the year, when people complain that they do not have enough food or enough of a particular food; (3) some members of the population usually do not have enough to eat; and (4) most members of the population usually do not have enough to eat—i.e., they are chronically undernourished; (8) don’t know.

However, when we decided to distinguish between chronic seasonal and nonseasonal scarcity, we realized that societies scoring 3 or 4 (to be conservative, we recoded all those scoring 2.5 or more) needed to be recoded because they could have chronic seasonal as well as nonseasonal hunger. The resulting scales were chronic seasonal scarcity: (1) absent—either because hunger was judged low or rare (1–1.5) or (2) present—either coded “hungry times” during the year (1.75–2.25 on the original scale) or “present” if original scores were 2.5 or higher. Chronic nonseasonal scarcity was a three-point scale: (1) absent (1–2.25 on the original scale); (2) moderate (2.5–3 on the original scale); and (3) high (3.5–4 on the original scale).

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Ember, C.R., Adem, T.A. & Skoggard, I. Risk, Uncertainty, and Violence in Eastern Africa. Hum Nat 24, 33–58 (2013). https://doi.org/10.1007/s12110-012-9157-5

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  • Warfare
  • Resource unpredictability
  • Resource scarcity
  • Eastern Africa
  • Resource-taking
  • Atrocities