Evolutionary psychologists have hypothesized, inspired by evolutionary biol
ogy, that parents should care less for children with whom they are not gene
tically related since these young do not contribute to the genetic fitness
of the parents. Based on this, evolutionary psychologists have predicted th
at there: will be an overrepresentation of step-parents as offenders in fam
ily-related killings of children. Data on child homicide, particularly from
Canada, have supported this prediction in that the frequency of children k
illed was relatively high in families where one of the two parents was a st
ep-parent. Here we present a survey of all child homicide that occurred in
Sweden between 1975 and 1995. In contrast to the Canadian data, children in
Sweden living in families with a step-parent were not at an increased risk
compared with children living together with two parents to whom they were
genetically related. In addition, there were no other indications that step
-parents are overrepresented as offenders.