FAMILY VIOLENCE A DARWINIAN PERSPECTIVE By: Nicole Kessler

Fairy Tales  The narrative histories of western cultures have been rife with evil step-parent tales (Hansel and Gretel, Sleeping Beauty, Snow White, & Cinderella).  Are these stories completely fiction or are they representative of a real phenomenon?

Class Predictions  Are step children treated the same as biological children?  Given what we know now about evolutionary psychology what would you predict?

Concepts to Consider  Inclusive Fitness: Is an organism's direct fitness (how many of its own offspring it produces and supports) plus it’s indirect fitness (the fitness individuals derived from increasing the survival of their relatives' offspring, whom share some percentage of their genes).

Concepts to Consider  Parental Investment: Any expenditure that benefits the offspring at the cost of the parents well being, other offspring, or future parental reproductive abilities.

Compelling Examples from the Animal World  Male yellow-headed blackbirds will adopt the offspring of another male, only when this allows the new male access to the female.  It is considered a mating display for the male to show what a great parent he would be.

Compelling Examples from the Animal world  But male barn swallows kill the offspring of other male swallows.  This scenario is significantly more common in the animal kingdom.

Compelling Examples from the Animal World  When a male lion acquires a new pride, he will often kill offspring that are not his own.  Cubs are in the most danger  This is advantageous to the male lion for two reasons 1. Resources will not be diverted to raising a non- related cub. 2. Female lions will enter estrus more quickly, allowing the new male lion to impregnate her.

Humans  Except in rare cases, such an overt and brutal practice would not be accepted.  Murdering your new spouses children will generally limit your access to your new spouse and hence your ability to produce more offspring.  Are humans so rationally and humanely evolved that this effect has disappeared?

Daly & Wilson  In the 1970’s two Canadian Psychologists, Martin Daly and Margo Wilson, began researching the question of variations in parental solicitude.  Daly & Wilson predicted that step-parents would feel less inclined to care for their step-children than natural parents.  Lack of care towards a child increases the likelihood of abuse. Abuse is what Daly & Wilson measured.

Disclaimer  We are not talking about every step-parent, step- child relationship.  Most step-parents are not abusive.  Daly & Wilson are looking at the extreme malfunction of the step-parent step-child relationship to see if there is a pattern of step- parents having less parental solicitude.

Daly & Wilson  Child abuse cases validated by American Humane Association in 1976 expressed as rated per thousand like-aged children in the reporting areas.

Daly & Wilson  Daly and Wilson also looked at child abuse in homes in Hamilton Ontario in the early 1980’s.

Daly & Wilson Child Abuse Cases handled by the children’s aid societies of Hamilton-Wentworth expressed as rates per thousand like-aged children in the region.

Daly & Wilson Conclusions  As you can see the Canadian child abuse data showed a very similar distribution to the American child abuse data.  Results showed that children in homes with one step-parent and one biological parent were 40 times more likely to be abused than children in homes with two biological parents.

Possible Confounds?  People who get divorced (and hence remarried) are just more violent.  Poverty  Reporting Bias

People who divorce are more violent overall.  This argument does not stand up in the face of selective abuse.  In the Hamilton study there were 10 homes that had both step-children and children from the current marriage. In 9 out of the 10 ONLY the step child was abused.  Lightcap, Kurland and Burgess (1982) gathered observational data on known abusive families in rural Pennsylvania, and consistently found ONLY step- children being abused.

Poverty  Daly and Wilson found that the SES status of two biological parent households showed a similar distribution to households with one step and one biological parent. Poverty is not a confound.

Reporting Bias  Reporting Bias—It’s possible that step-parents don’t actually abuse more often just that it is reported more often. This is a difficult confound to overcome when doing archival research.  Daly and Wilson argue that reporting bias is almost eliminated in homicide cases.

Homicide Data  In an analysis of data from there were 43 Canadian 1 year old killed by ‘parents’.  11 of the 43 (25.6%) were killed by step-parents.  If step and natural parents killed at the same rate the expected rate would be under 1%. (Daly & Wilson ’85)

Homicide Data  Daly & Wilson analyzed all homicides of pre-school aged children in Detroit in  Their analysis revealed that 4 of the 7 murders were committed by step-fathers that’s 57%. (Daly & Wilson ’82)

Homicide Data  Scott reviewed data on British ‘fathers’ who killed their children (under 5 years old)  He found that 15 out of 29 British ‘fathers’ who killed their children were in fact step-fathers, again 52%. (Scott ‘73)  Over representation of step-parents in infanticide cases.

Why young children?  They are more vulnerable and less able to defend themselves.  From the step-parents point of view infants will demand the most resources (as compared to say adolescents).  The bond with children grows as they get older (remember Selena’s presentation), maybe the natural parent is more likely to protect older children.

Summary  It’s been shown that children living in homes with both step and natural parents are at a higher rick for abuse and homicide than children living with two natural parents.  Younger children are at an even higher risk for both abuse and homicide.

Summary  Taking into consideration…  Inclusive Fitness & Kin Selection,  Parental Investment Theory  Animal Models  And the data presented today  It follows from a Darwinian framework that…

Summary  Parental solicitude varies as a factor of relatedness to the child.  People don’t like others children as much as they like their own so…  People are not willing to make as many sacrifices for others children  and in extreme cases will harm or kill those children.

Conclusion  Fairy Tales are true!

Sources Cited  Daly, M, and Wilson, M. "The Darwinian Psychology of Discriminative Parental Solicitude." Nebraska Symposium on Motivation 35(1988):  Daly, M, and Wilson, M. "Violence against stepchildren." Current directions in psychological science 5.3 (1996):  Daly, M, and Wilson, M. “Discriminative Parental Solicitude - A Biological Perspective." Journal of Marriage and Family 42.2 (1980):  Daly, M, and Wilson,M.. "Some Differential Attributes of Lethal Assaults on Small Children by Stepfathers versus Genetic Fathers." Ethology and sociobiology 15.4 (1994):  Daly, M, and Wilson, M. "An assessment of some proposed exceptions to the phenomenon of nepotistic discrimination against stepchildren." Annales zoologici Fennici (2001):  Hamilton, L., Cheng, S, and Powell, B. "Adoptive parents, adaptive parents: Evaluating the importance of biological ties for parental investment." American sociological review 72.1 (2007):  Lightcap, J.L., Kurland, J.A., and Burgess, R.L. Child Abuse: A test of some predictions from evolutionary theory. Ethology and Sociobiology, 1982, 3:61-67

Sources Cited  Daly, M, and Wilson,M.. "Some Differential Attributes of Lethal Assaults on Small Children by Stepfathers versus Genetic Fathers." Ethology and sociobiology 15.4 (1994):  Daly, M, and Wilson, M. "An assessment of some proposed exceptions to the phenomenon of nepotistic discrimination against stepchildren." Annales zoologici Fennici (2001):  Hamilton, L., Cheng, S, and Powell, B. "Adoptive parents, adaptive parents: Evaluating the importance of biological ties for parental investment." American sociological review 72.1 (2007):  Lightcap, J.L., Kurland, J.A., and Burgess, R.L. Child Abuse: A test of some predictions from evolutionary theory. Ethology and Sociobiology, 1982, 3:61-67

…FIN Questions, Comments, Concerns?