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

animal navigation bandura behaviorism dogs ethology evolutionary psychology skinner social learning theory trains vicarious learning

Ranger the Beagle Takes The A Train

If you love dogs than you are sure to have stories, like the one of my Shih Tsu, Buster, that would jump onto my daughter’s bed when I left for work and at about the time my wife or I would return home, gaze out the window, and jump down from the bed so that we could not punish him for violating the rule of the house. My friend, Andrew, had Beagles Honey and Ranger that were smarter than Buster because they would travel throughout our neighborhood looking for food, swimming in the golf course pond, and then return home to rest. Then Andrew told me about the dogs in Russia who travel the subway and prefer the first and last cars which are the most quiet so they their sleep is uninterrupted.

According to Russian psychologist, Dr Andrei Poiarkov of the Moscow Ecology and Evolution Institute, these dogs had to move to the suburbs when after the collapse of the Soviet Union in the early 1990s the industrial complexes that were the dogs’ shelters went to the suburbs. The dogs had to figure out how to get back to the city’s center where the food was plentiful. There are reports that the dogs will startle pedestrians to drop their shwarma, a meat snack on a stick, with a bark from behind. They time the trip to get off at the most desired stop, and they walk when the light is green (dogs have no cones in their retina so they do not see color so they probably time their curb crossing to correspond to the picture of the walker or to the crossing of people).How are we to explain the bizarre behavior of the subway riding dogs? Russian scientists have a history of studying dogs. The most notable is Noble prize winner, Ivan Pavlov, who discovered classical conditioned learning. However, the train traveling dogs are best explained by American Psychologists Edward Thorndike and B.F. Skinner who discovered operant conditioning. According to Thorndike, behavior followed by a positive consequence or reinforcement is more likely to occur (The Law of Effect). Learning is incremental and trial and error. All mammals learn in the same way, by doing. Doing strengthens the learning (Law of Use) and not doing weakens the connection between the stimulus and the response (Law of Disuse). Extending these laws, Skinner “taught’ pigeons to read and guide missiles to their target.

In addition, Albert Bandura described vicarious learning when an organism learns by watching another organism (modeling). The organism’s expectancy to be able to do what another organism does is self-efficacy.

So the dogs moved to the suburbs, but the center of the city was where their food was most plentiful. By linking their travels outside their suburban home with the finding and eating of food they learned to get back to the city center where food was most plentiful. According to the principles of evolutionary psychology the healthiest dogs that could most efficiently use their innate ability to navigate were most likely to survive, and it is this inborn will to survive which cues other dogs to do what they see their fittest brethren doing. The dogs watch other organisms, humans, getting on trains and going where they want to go or by accident discover that they can go towards the city on a train (a mode preferred to hoofing it) and ride in quiet (the front and rear cars) and conserve the energy that will be needed to forage for food. Crossing with others in the crosswalk with the green symbol avoids getting struck by a car or bus (and those that don’t learn, aren’t around so the lesson is obvious). There you have it! Dogs learning to ride the rails become an illustration of the principles of evolutionary, operant, and social cognitive learning and are no more bizarre than missile guiding pigeons.

Further Links: