Daly & Wilson (1985): Child abuse and other risks of not living with both parents. Ethology & Sociobiology Evolutionary hypothesis: Parental feeling should vary with prospective fitness value of child to parent when step-parent is called to fill parental role toward unrelated child, we may anticipate “an elevated risk of lapses of parental solicitude” (inc. child abuse) Previous studies had various problems. (1) confound with SES (2) is abuse a specific effect or just one aspect of a bad rearing environment (“broken home” syndrome)? – test: compare parent+step - parent households with single parent households.

Daly & Wilson (1985): Child abuse and other risks of not living with both parents Hamilton, Ontario. Called homes in survey to get base-rates on family composition (2 natural parents; 1 natural + 1 step; 1 natural alone). Used postal code to tag with SES. Child abuse sample: 99 kids (info: children’s aid societies) Police sample: 542 kids (99 runaways, 449 criminal offenses) Had household composition data for these cases. Two data sets combined to give rates.

1. What is the theoretical rationale of this study? How would you state their hypothesis? 2. What is the purpose of the “police” sample? Does it effectively serve its purpose? 3. This paper is neither good news nor good press for step- parents. What might an advocate for step-parents find in this paper to mitigate the bad news? 4. Comparing child abuse and infanticide in humans (see figure from Daly & Wilson book on homicide) with infanticide as seen in langurs and lions, in what way are they similar, and in what way are they fundamentally different? 5. Can you think of an alternative hypothesis to explain the data in this paper? Be careful not to confuse ultimate-level and proximate-level explanations! 6. If you can think of an alternative hypothesis, how would you test it?