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STEP-PARENTS are no more likely than biological parents to murder their
children, according to Swedish researchers. This flies in the face of Canadian
findings from over a decade ago, which indicated that having a step-parent is
the single greatest risk factor for being maltreated as a child.

In 1988, psychologists Margo Wilson and Martin Daly at McMaster University in
Hamilton, Ontario, published a landmark paper showing that young children living
with at least one non-biological parent were 70 times as likely to be killed as
children living with both their biological parents. Wilson and Daly’s study
looked at 147 children who were murdered in Canada between 1974 and 1983 and
concluded that evolutionary biology was at work: parents don’t squander
resources on children who are not their genetic offspring.

Now Magnus Enquist and his colleagues at Stockholm University dispute those
findings. They looked at 139 Swedish children killed by a parent figure between
1975 and 1995. The researchers broke the families into four groups: those raised
by two biological parents, a single biological parent, a biological parent and a
non-biological parent, and two non-biological parents.

They found that in families with two parents there was no difference in the
risk of children being killed, regardless of whether they were biologically
related. “We were a bit suspicious of Daly and Wilson’s conclusions, in
particular their sharp effect,” says Enquist. “But the fact that we couldn’t
find anything was also a surprise.” Folklore is filled with stories of evil
step-parents, he points out.

Living with only one parent, however, did represent a danger. Children raised
by a single biological parent were at four times the risk of dying in
family-related violence as children of two parents. But many of the single
parents who killed their child also had psychiatric problems or abused drugs,
Enquist found.

In three of seven cases where the victim had one biological and one
non-biological parent, the genetic parent had committed the murder. Overall, the
researchers say, non-genetic parents were not over-represented as offenders.

Non-genetic offenders account for 29 per cent of child homicides in Canada
and only 7 per cent in Sweden—despite the fact that the proportion of
children living with step-parents is four times as high in Sweden as in Canada.
Sweden’s long history of legal abortion and low rate of unwanted pregnancy may
explain some of the difference, but Enquist says the apparent disparity between
the two countries is so enormous it must be further investigated.