Can Evolutionary Principles Explain Patterns of Family Violence?

1. Can Evolutionary Principles Explain Patterns of Family Violence? Archer, J. (2013). Can evolutionary principles explain patterns of family violence?. Psychological Bulletin, 139(2), 403-440. doi:10.1037/a0029114

2. Intro • “Violence within families is an extensive field of study whose research has wide-ranging implications for social policy” (Archer) • Focus on violence, subset of aggression • Application of evolutionary principles to research on family violence • Kin Selection – Adaptive for animals to distinguish kin from non kin

3. Evolutionary Principles & Family Violence • Degree of shared kinship and Reproductive Value (RV) • Age, resources, and offspring quality • Resource Holding Power (RHP) • Characteristics of individuals engaged in conflicts

4. Kin Selection • Kin are more likely than unrelated individuals to cooperate and less likely to compete, since altruistic behavior provides a way of perpetuating shared genes (W.D. Hamilton) • Inclusive Fitness • Parents care for offspring because they share genes that are rare in population • Hamilton’s Rule • Evolutionary costs and benefits • Benefits of helping a relative X coefficient of relatedness = costs • High rates of violence among step families • Kin Recognition • Animals must learn to differentiate kin • Assessment of the degree of resemblance • Facial resemblance = more cooperation and greater attraction

5. Reproductive Value (RV) • RV is a measure of how likely individuals are to contribute to future generations • Offspring are more important to parents as a means of perpetuating genes than parents are to offspring • As offspring grow older, they become more valuable to parents • As parents grow older, their RV drops • Rates of violence • Offspring most at risk early in life, parents at risk the older they come

6. Attachment & Selective Investment • Focus on offspring’s bond with his/her primary caretaker • Family violence • Attachment bond acts as an inhibitory influence on the motivational system underlying aggression

7. Resource Holding Power (RHP) • Game theory model of the evolution of animal fighting (Parker, 1974) • Evaluating potential opponents fighting ability and act on information – fight or flee • Fighting ability = RHP • Assessing RHP and acting accordingly are an evolutionarily stable strategy (ESS; Maynard Smith, 1982) • RHP throughout the lifespan • Father son reversal of RHP

8. Violence Between Parents, Offspring, and Siblings • Parental violence to unrelated Children • Reconstituted families are “crucibles for conflict” (Emlen, 1997) • Inclusive fitness • Degree of genetic relatedness • Higher rates of physical violence to children with stepparent across cultures • Higher risks from stepparents for homicide (Daly and Wilon, 1988) • Hostile rather than instrumental killings • Beating vs. suffocation, drowning, strangling, shooting, followed by suicide

9. Violence between Parents, Offspring, and Siblings Cont. • Parental violence to genetic children • Parent offspring conflict model (Trivers, 1974) • Conflict will arise from offspring seeking more resources from parent • RVp • Reproductive value of parent decreases so parents value children more • Decline in parent abuse as parent grows older • RVc • Reproductive value of child is low early in life, but grows • Risk of abuse and neglect by parents higher for offspring’s early years, and then declines • Paternity Uncertainty • Facial resemblance

10. Violence Between Parents, Offspring, and Siblings Cont. • Offspring’s Violence to Parents • As parents RV declines, offspring’s RV rises • Parents contribution to offspring’s fitness decreases • Parents RHP decreases as offspring’s RHP increases • Aggression to parents is frequent at young ages, but declines • Children express themselves physically, but learn to inhibit • Increase in offspring to parent homicide in 20’s • Increase in offspring RHP • More violence to stepfathers

11. Violence Between Parents, Offspring, and Siblings Cont. • Violence Between Siblings • Inclusive Fitness • Predicts that genetic siblings will have less conflict than unrelated siblings • Confirmed in one study, more research is needed • Physical aggression is frequent between siblings, but generally at low levels • At young ages when aggression was common, older siblings showed more of it • RHP • Homicide most often occurs later in life between siblings • Greater tendency for siblings to cooperate and kill unrelated people

12. Violence Between Partners • Partner violence as mate guarding • Paternity Uncertainty • Male doesn’t want to raise child that is not potentially his • Built in behavioral measures to maximize paternity certainty • Absence of sex difference in physical aggression to partners • Greater male – female violence found only in low gender empowerment nations • Findings support broader view – both sexes show mate guarding tendencies • Men want to avoid raising an unrelated child, women don’t want to lose a helper/protector

13. Summary & Conclusions • Kin Selection • Greater risk of violence toward stepchildren than genetic children • Some parents showed abuse to stepchildren and not their genetic children • Weaker affective bonds with stepchildren • Reproductive Value (RV) • Violence by parents highest in infancy and decline through childhood • Supported for both violence and homicide • Supported by cues to poor physical prospects for child and shortage of resources • Decline in parental RV with age • Risk of violence to offspring declines • Risk of violence from offspring increases

14. Summary and Conclusions Cont. • Resource Holding Power (RHP) • Older siblings generally initiate more physical aggression than younger ones • Boys moreso than girls • Sibling with lower RHP seeks help from parents • Reversal in parent-offspring violence in teenage years for boys • Partially supported • Increase in lethal violence in 20’s in case of sons to fathers

15. Questions? • What are your thoughts on the research?