evolutionary psychology familicide infanticide mass killings Mesac Damas step parents

Familicide – Evolutionary Origins

In our last post we reported about the case of infanticide (or fililcide) where a man involved in a bitter custody dispute killed his children and then took his own life. With the reporting of a similar case in Florida, this time representing familicide where the entire family was killed by a parent, I thought perhaps it might be worthwhile to try and understand the roots of this behavior.

Mesac Damas recently killed his wife and five young children and then fled to Haiti where he was caught. Supposedly while awaiting extradition back to the U.S., he confessed to the murders. When asked why he did it he responded “Only God knows”. The murders were especially brutal with Sheriff in charge of the case calling them “the worst of the worst”. Damas had a history of domestic violence and apparently thought his wife was cheating on him with another man.

In a fascinating 1995 paper by Wilson, Daly, and Daniele, the authors delineate some of the characteristics of familicide- i.e cases in which a spouse kills an entire family and sometimes themselves. In an examination of 109 incidents of familicide in Canada and Britain the authors found that familicide is most often perpetuated by men. Half of these male perpetrators killed themselves which is a much higher percentage than men who kill only their wives, or just their children. In cases of familicide the parents are more likely to be living together as opposed to being married. Step children are more likely to be victims of familicide than genetic offspring. However, men who kill step children almost never kill themselves. The authors conclude with a tentative categorization of familicidal incidents into two types – accusatory or despondent. As the authors explain:

The hostile, accusatory familicidal killer is often enraged at the alienation of his wife, and may declare that “If I can’t have her, no one can.”The despondent familicide perpetrator instead appears to believe that his victims could not persist or cope in his absence, and that their deaths are therefore necessary, perhaps even merciful, corollaries to his suicide. In either case, the killer apparently feels entitled to decide his victims’ fates.” p. 15

The Florida case presents many of the characteristics outlined in this paper. The killer was male, he and his wife had been living together for a long time and had only recently been married. He fit the pattern of an accusatory killer who was outraged that his wife may have been cheating on him. What we do not know is whether he suspected that any of his wife’s children were by another man, but it wouldn’t be surprising.

Why would this be important? It is well known that violence against children in a family is more likely to be perpetrated by a step parent. In another paper Daly and Wilson (1994) found that step fathers were more likely to beat step children to death, while genetic parents were more likely to shoot or asphyxiate their offspring. The genetic fathers were also more likely to commit suicide.

As David Buss writes in Evolutionary Psychology: The New Science of the Mind, genetic relatedness is a strong predictor of not only how many resources a child receives but also of how likely they are to be abused. The closer the genetic relationship, the more likely the child is to receive resources and not be abused, while the more distant the relationship the more likely the child is to be abused and not receive resources. This pattern comes from our evolutionary history. Male primates such as chimpanzees are known to kill other males’ offspring which precipitates the females going into heat. The killer males will then mate with the females to produce their own offspring. This pattern of behavior presumably originated in the common ancestor to humans and apes. It had survival value and so continues to be found in humans and primates today.

In her book The Chimpanzees of Gombe: Patterns of Behavior, noted biologist Jane Goodall describes numerous incidents of infanticide by both males and females among chimpanzees. In general she believes that many of the attacks are focused on the mothers of the infants and are related to a distrust and aversion to strangers. Yet males appeared to also attack and sometimes eat infants of females so as to bring the females into heat sooner. Interestedly, young unattached females from other groups were only attacked mildly, while older females who were not in heat and who had infants were attacked quite severely and even killed.

Unfortunately for us, we find these evolutionary patterns of killing writ large in humans. A quick examination of mass killings around the world reveals this pattern in ethnic cleansing and warfare. In World War II, the Soviets raped and killed on a massive scale (the Germans while brutal killers did not commit as much rape). The degree of infanticide and rape during the recent ethnic violence in Rwanda has also now been documented. And of course it is quite easy to find more examples.

This is not to say that step parents are murderers, child abusers, bad parents (most are not) or that in our society familicide is common (it is not). But is does remind us to be aware of the possible pre-cursors to this type of violence and to be cognizant of things that may trigger this behavior.

– Kevin


Davies, N. (2007). No Simple Victory: World War II in Europe, 1939-1945. New York, NY: Viking.

de Brouwer A., & Ka Hon Chu, S. (Editors). (In Press). The Men Who Killed Me: Rwandan Survivors of Sexual Violence. Vancouver, BC: Douglas & McIntyre.

Buss, D. (2008). Evolutionary Psychology: The New Science of the Mind. Boston, MA: Pearson.

Daly M, Wilson MI (1994) Some differential attributes of lethal assaults on small children by stepfathers versus genetic fathers. Ethology & Sociobiology 15: 207-217.

Goodall, J. (1986). The Chimpanzees of Gombe: Patterns of Behavior Cambridge, MA: Harvard University Press.

Wilson M, Daly M, Daniele A (1995) Familicide: the killing of spouse and children. Aggressive Behavior 21: 275-291.

Further Readings:

Publications by Martin Daly and Margo Wilson