Stepparents are not always evil: Parents' strategy to love their children depends on more than blood ties
Contrary to common belief, parents do not generally treat their stepchildren less favourably than their own. Until now, many researchers believed in the so-called "Cinderella effect." It states that it is biologically inevitable that parents care less for stepchildren because they do not spread their genes. Researchers at the Max Planck Institute for Demographic Research (MPIDR) in Rostock, Germany, have discovered an important exception. If there is a reasonable chance of increasing wealth in the parents' environment then no difference is made between one's own children and stepchildren. Thus, parental care depends on more than just the biological relationship.
This is the result of a study published by MPIDR researcher Kai Willführ together with Alain Gagnon from the University of Montreal, Canada, in the scientific journal "Biodemography and Social Biology." "We are now able to prove that the Cinderella effect is not an inevitable reflex of stepparents," says Kai Willführ. The scientists investigated if and how strongly parents neglected their stepchildren by looking at the mortality of children in historic patchwork families from the 17th to 19th century. They compared the Krummhörn region of East Frisia (Germany), which was a densely populated area with little space for economic development, and the growing Canadian settlements in Québec. For both areas they calculated how the children's chances of survival changed when a stepmother moved in.
The conclusions showed that only in Krummhörn, which offered fewer opportunities for economic growth, the stepmother had a negative influence. In Krummhörn children from a father's first marriage died more often before the age of 15 if a stepmother moved in. This effect was not seen in Québec. The "Cinderella effect," therefore, does not inevitably seem to occur. The stepmothers must have treated their children in East Frisia and Canada completely differently.
When do stepchildren die young?
The extent of this effect is striking: if a Krummhörn girl lost her mother early, the likelihood of her dying before the age of 15 more than doubled compared to a girl whose mother did not die. If the father remarried and the stepmother joined the family, mortality doubled again. Thus, the arrival of a stepmother affected the girls in East Frisia as much as the death of their own mother. In Québec, however, the risk of dying young barely changed when the new mother moved in.
"The stepmothers in Québec seemed to understand that the offspring from their husband's first marriage were not competition for their own children with their new husband," says MPIDR researcher Kai Willführ. In fact, the Canadian half siblings were considered to be allies of the biological children. On the contrary, according to the "Cinderella effect", stepparents would always consider foreign children to be competitors to their own children and thus neglect them.
Love for children is strategy
But that only happened in Krummhörn, where siblings competed for basic needs. "We assume that stepmothers neglected, exploited or even abused the children from their husband's first marriage," says socio-biologist Willführ. The fact that this only happened in East Frisia shows that the context in which patchwork families are living - whether there is room for economic development or not - strongly influences how parents allocate their affection to their own children and stepchildren.
Although the scientists used historic data, their results have fundamentally challenged the veracity of the "Cinderella effect. "It is therefore also true today, that stepparents are not always evil," says researcher Kai Willführ. For their study, Willführ and Gagnon traced thousands of children up to age 15 in East Frisia and Québec. By individually reconstructing whether and when a parent died, a stepmother or stepfather moved in, and whether half-siblings were born during this period, they were able to calculate the influence of all those events on the survival rate of boys and girls. Dates of births, christenings, weddings and funerals were taken from old church registers. For the Krummhörn region in East Frisia the researchers looked at the birth cohorts from 1720 to 1859, and for Québec at those from 1670 to 1750.