Martin Daly and Margo Wilson’s research into the clearly identified risks that stepparents pose to their stepchildren has led to some of the most influential and path-breaking insights to emerge in the past three decades in the field of human psychology and evolutionary psychology.
The two Canadian-born researchers found overwhelmingly powerful evidence globally that stepparenthood has “turned out to be the most powerful epidemiological risk factor for child abuse and child homicide yet known.”
What’s more, they conclude in their influential 2002 paper, The Cinderella Effect: Parental Discrimination Against Stepchildren (1), that “non-violent discrimination against stepchildren is substantial and ubiquitous.”
Daly and Wilson turn to the research done widely in non-human species on Darwinian selection. Under this model of “the selfish gene,” the care of dependent young will ordinarily be directed selectively toward close relatives of the caretaker.
Daly and Wilson write that “psychological adaptations that produce discriminative parental solicitude vary between species, in ways that reflect regularities in each species’ ancestral environment of evolutionary adaptiveness (EEA).”
According to Daly and Wilson, “there is nothing magical about parental discrimination: preferential treatment of one’s own young exists only where a species’ ecology demands it.” The two see no reason why the evolution of the human psyche would be excluded from this logic.
Daly and Wilson’s wealth of evidence
Daly and Wilson’s research provides clear epidemiological evidence, including the use of an archive of 87,789 validated reports of child maltreatment in the United States. They support their findings with dozens of peer-reviewed studies of stepparenting abuse across cultures that also find similar patterns of abuse and stress.
These findings have yet to be refuted in any serious peer-reviewed paper. They are constantly cited by critics, who fail to show any new evidence refuting their findings.
Daly and Wilson’s research also went well beyond lethal and abusive treatment of children by their non-genetic parents. The outcomes they list include show how medical care is restricted, education funding is withheld, and other forms of non-physical abuse and favoritism prevail. Some of the main findings include:
- In several countries, including Canada and the United States, stepparents beat very young children to death at per capita rates that are more than 100 times higher than the corresponding rates for genetic parents.
- Children under three years of age who lived with one genetic parent and one stepparent were estimated to be seven times as likely to be the victims of validated physical abuse as those living with both their genetic parents.
- In a Korean study of schoolchildren in the 3rd and 4th grades, 40 percent of those living with a stepparent and a genetic parent were reported to be “seriously battered” once a month or more, compared to 7 percent of those living with both their genetic parents.
- In Finland, 3.7 percent of 15-year-old girls living with a stepfather claimed that he had abused them sexually, compared to 0.2 percent of those living with their genetic fathers.
- Consistent findings of research show that stepparents and stepchildren alike rate their relationship as less close and less dependable emotionally and materially, and that all parties in stepfamilies are less satisfied, on average, than persons living in intact first families.
- Stepchildren suffer elevated rates of accidental injury, both lethal and nonlethal, from infancy onwards, likely because they are not monitored and protected as closely, and they experienced elevated mortality in general, not just from assaults.
- Research in the island of Dominica has shown that stepchildren have chronically elevated levels of the stress hormone cortisol, which is strongly associated with worse health outcomes in nearly all categories.
- Numerous American studies, controlled for parental means, have demonstrated that children living with stepmothers do not receive the same regular medical and dental care than children living with their genetic parents.
- Less money is spent on food in stepmother households.
- Fiscal support from families for higher education is substantially reduced for stepchildren, even when both parental wealth and the child’s scholastic record are statistically controlled.
Fantasy land, the Brady Bunch, bears little resemblance to the complex reality of stepparent and stepchildren relations.
Weighing the evidence, Daly and Wilson also note that most stepparents also find pleasure helping to raise the children of their partners, and that many stepchildren are better off in stepfamily situations than those where the parent did not remarry. However, they write stepparents do not feel the same “selfless commitment” common in genetic parents.
In response to their critics, Daly and Wilson cite that literally “hundreds of self-help manuals for stepfamily members” all focus on the difficult issue of how to cope with the characteristic conflicts of stepfamily life.
Research continues to verify findings of Daly and Wilson
Other researchers besides Daly and Wilson continue to verify their findings. For example:
- Schnitzer and Ewigman (2008) in the Journal of Nursing Scholarship found that children residing within households with adults unrelated to them had nearly six times the risk of dying of maltreatment-related unintentional injury. But risk was not higher for children in households with a single biologic parent and no other adults in residence.
- Stiffman, Schnitzer, et al. (2002) in the journal Pediatrics reported that children residing in households with adults unrelated to them were eight times more likely to die of maltreatment than children in households with two biological parents.
- Harris, Hilton, et al. (2006), in a study of 378 cases of filicide (killing one’s son or daughter), found that at least five times as many of the child victims lived with genetic fathers, while the raw frequencies of filicide were roughly equal between stepfathers and biological fathers.
- Tooley, Karakis, et al. (2005) reported that step-children under 5 years of age were at a significantly increased risk of unintentional fatal injury of any type, and of drowning in particular. They also reported that children from single-parent families were generally not found to be at significantly increased risk of intentional or unintentional fatal injury, while children who lived with neither of their biological parents were at greatest risk overall for fatal injury of any type.
- A 2008 Scottish Government study found that living in a “reconstituted” family with step-children or stepparents increased the risk of developing behavioral problems.
The danger of ignoring the myth (that is backed by evidence)
The research by social scientists and epidemiologists undermines the Brady Bunch myth of a balanced family involving parents and children with no genetic relations—the guys in this family having no genetic relations to the girls. The more appropriate model to discuss the validty of research is the older and still maligned trope of an evil stepparent, notably the stepmother, as clearly acknowledged by Daly and Wilson in referencing Cinderella in their research title.
The wicked stepmother is a frequent character in folklore. This myth is older than feudalism, and found globally. The darker Brothers Grimm version of Cinderella (Aschenputtel) has her stepmother’s cruelty on full display, compared to simply wickedness in the Disney rendering. A recent cinematic evil stepparent was captured in the classic Cold War film thriller The Manchurian Candidate, which included an evil stepfather in partnership with his Soviet spy wife to manipulate her son to kill a presidential candidate and advance a dark Soviet conspiracy.
Joseph Campbell, author of Hero with a Thousand Faces, notes that myths incorporated the tools that people used, and those tools are associated with power systems that are involved in the culture of their time. In the case of the trope of the evil stepparent, the myth has not been supplanted. Evidence shows otherwise. It is still alive for good reasons.
Why this matters for policy makers
There continues to be great stepparents and foster parents, by the thousands. I know many great people in both camps. They deserve praise for doing a job that may have few rewards and tremendous stress. I am in awe of those who I personally know (colleagues in Alaska).
However, policy makers, educators, law-enforcement agencies and social service agencies need to be reminded of very real risks of some family situations. The New Zealand-based nonprofit called Child Matters notes that having a stepparent is a known risk that should be considered for the well being of all children.
Efforts by “soft” social science publications, like Pscyhology Today, to downplay the valid research into the hazards stepfamilies can pose to innocent children do not help the group that needs the help most of all.
Our larger understanding of stepparenting should not, as Daly and Wilson write, “suffer from the misconception that a ‘biological’ explanation for stepparental violence is a claim of its inevitability and imperviousness to social controls, which, if accepted, will excuse the violence.”
They rightly claim that these misunderstandings block progress in understanding and helping kids. Acknowledging the evolutionary process and its relevance to human affairs can only help. I believe Daly and Wilson are spot in their claim that the most harm is done by “those who adhere to the implausible notion that stepparenthood is psychologically equivalent to genetic parenthood and that ‘bonding’ experience is sufficient to evoke the full depth of parental feeling.”
(1) Daly M & Wilson M (2002). The Cinderella effect: parental discrimination against stepchildren. Samfundsøkonomen 2002 (4): 39-46.
Rudy Owens' Blog 
I felt the need to post after reading your blog article ‘The Cinderella Effect’. I have been at both ends of this. I was a child born to an unwed mother, she married a man when I was 2, who later adopted me. He Never wanted me, and the abuse I suffered at his hands lasted until I ran away at 16 years old. His child , my half sister was his world..and he showered her with all the love, praise and support a parent should. I on the other hand spent countless days having to stay home from school, the bruises were far to obvious. In the late 60’s early 70’s people tended to look the other way. And you just didn’t talk about it.
I went on to marry twice, and have 2 beautiful children whom i never abused. I gave them what i never had, unconditional love.
I remarried at 40 years old, to a man raising 3 children alone. Now I was the step parent. I dove head first into being the best parent I could for the children. Having known the despair and fear i felt as a child, I never wanted them to feel anything but loved.
It should have worked…..
My new husband was very controlling and abusive. By year two my stepchildren were abusing me. I was being hit, lied to, lied about, emotional and physical abuse, all over again. I almost neglected my own (older) children to make sure my step children were happy.
They never were, and the abuse towards me continued until I finally had enough. I was so close to breaking, my mental health was shattered, my ptsd was full blown, and I was battered.
Leaving felt like I had failed. However to survive I had to.
I live alone now, at 60 years old. My grand daughter and adult kids visit, and we are happy.
I live in the country, I have too many cats, and I have peace at last.
Alice, thanks for sharing. I’m sorry you had to experience these very difficult circumstances. The data, as my article highlighted from many researchers, are very clear why genetics matter in parent/child relationships. I talk about that in my newly published memoir/examination of the American adoption experience (www.howluckyuare.com). You are not the only one who experienced this, and there are reasons that it occurred beyond the people involved too. Sounds like you had a lot of grit and can give yourself credit for that. To me, it sounds like you succeeded–not failed. I hope you can look back on your life with some peace knowing your kids and grandkids are a loving part of your life. Best regards.
My stepmom was not the easiest person to be around. I always thought she suffered from bipolar, but as I never had the ambition to educate myself as a medical doctor, I was not in the position to give an official diagnosis. “Bully” comes to mind when I think of her. There was a clear difference in the way she engaged with her biological children and the demeaning manner she threated me and my sister. We became custom to walking on egg shells. Always trying to please her by obediently completing her wish lists, to hopefully, somehow receive some kind of recognition and affection. But we were mostly greeted by harsh words on how incompetent, stupid, ugly and “you are just like your mother” we were accompanied by a hiding we did not deserve.
My dad, business man by heart, was well traveled. In his way he conquered the business world but lacked the same ambition at the home front. Why he never stood up to take a stand, is till this day one of the most unanswered question. Why could her kids enjoy private school education with expensive extra mural activities, receive extravagant gifts, and sponsored holidays. But hypocritical stating that the bill for our school bus, that drives past to the local school 15km further, could not be paid. Riding my bicycle for 15km to school in winter, in the dark, with a schoolbag full of books, made me wonder “what did I do wrong?” and “Should I try harder?”. Just knowing that the 15km cycle return trip in the afternoon, I would reflect on the same questions. As this “you pulled the shortest straw” example became a repeated pattern year after year, serving the same injustice, unfairness and emotional manipulation.
Although I now understand my stepmother focused to provide her children the most nurtured environment and doing everything in her power to create favorable situations by exposing them to specific groups and ideal conditions, it left me and my sister as outsiders. Even as a child, I had an overwhelming feeling that I was less, I never felt part of a family. I quickly learned: You only speak when spoken to – literally. Obey every request rather than speaking up, mastering the fine art of knowing not to gamble when the odds were against me. I was an introvert dealing with my emotions by means of listening to songs I could relate to and writing poems that would describe how I feel without revealing too much to the outside world.
Sorry you experienced what you described. You still have a life to live that’s yours to choose. And, according to the evidence, what you experience is rooted in the biological dynamics of stepparent relations with non-genetically related children in their household.