Are the husbands of unfaithful women more likely to kill children they might unconsciously know aren't theirs?

In "Too Hard For Science?" I interview scientists about ideas they would love to explore that they don't think could be investigated. For instance, they might involve machines beyond the realm of possibility, such as devices as big as galaxies, or they might be completely unethical, such as experimenting on children like lab rats. This feature aims to look at the impossible dreams, the seemingly intractable problems in science. However, the question mark at the end of "Too Hard For Science?" suggests that nothing might be impossible.

The scientist: Jaimie Krems, a graduate student of cognitive and evolutionary anthropology in the doctoral track at the University of Oxford in England.

The idea: Fairy tales are rife with wicked stepmothers that do their utmost to kill their stepchildren. Grimly, murderous stepparents are real.

"Stepparents are six times more likely to abuse a child under 2 than biological parents are," Krems explains. "In the U.S., a stepchild is 100 times more likely to be killed from violent abuse than biological offspring, and in England, though only roughly 1 percent of babies live with a stepparent, 53 percent of baby killings are by stepparents."

These monstrous statistics have counterparts elsewhere in the animal kingdom.

"Male lions, for example, when taking over a pride, often kill cubs sired by other lions," she says. "This releases more of the pride's necessarily limited resources for their biological offspring and returns females previously concerned with feeding and caring for their young to sexual receptivity. The case is similar in some nonhuman primates."

Evolutionary theory predicts the more related you are to someone, the less likely you are to kill them, something that matches up with real-world statistics, Krems says. "The worst-case scenario, in evolutionary terms, is to waste resources on another man or woman's genetic material — that is, offspring."

The idea, then, is that evolutionary logic might explain what evolutionary biologists Martin Daly and Margo Wilson called the Cinderella effect. However, are social factors responsible instead, and this reliance on evolutionary theory no more than biological determinism? "Does that fact we humans have the tale of Cinderella telling us stepparents are supposed to mistreat stepchildren shape and direct how stepparents act?" Krems asks.

The problem: To really see if nature or nurture, biology or culture are responsible for the Cinderella effect, one would have to remove all cultural messages regarding stepparents, "and we cannot," Krems says.

The solution? One possible way to answer into this question is to investigate men "who believe — mistakenly or otherwise, considering estimates reveal that as many as one in 10 children are not the progeny of the man who believes he is the father — the child they murdered is biologically their own," Krems says.

"Once convicted of infanticide or child killing, simple genetic tests could reveal whether or not the deceased were the biological offspring of their murderers. All things being equal, I would bet, based on the evolutionary biological evidence gathered by Daly and Wilson and our bodies' ability to unconsciously 'know' far more information than that of which we are conscious — I believe this includes information on biological relatedness, possibly as communicated through the major histocompatibility complex — that mistaken fathers significantly 'outmurder' true biological fathers."

Such findings would have major implications for biological communication — how we know who is related to us, for example. It would also impact evolutionary psychology, revealing continuity in behavior between humans and other species, how and why we treat our biological kin differently, the "naturalness" of infanticide and would act as even more support for fundamental evolutionary theories and how they are borne out in human behavior even though we are largely unconscious of these effects, Krems says.

There could even be serious consequences for social work and perhaps even social policy, she adds. "Should children be allowed to live with stepparents; should children be placed in the custody of biological fathers by family courts more often than they currently are; should single-mothers intending to date be allowed to remarry; should paternity tests be given whether or not the man and pregnant woman believe there is paternity uncertainty?" Krems asks. (She does note that people who adopt are a self-selecting group distinct from stepparents who cannot typically disavow connection to a partner's unwanted offspring.)

However, "those policy questions may be going too far" and "this is not the kind of work that gets done," Krems says. "It is costly to carry out, especially as it may some time to come up with a large enough sample size. There are issues of race, socioeconomic status and the legal system to contend with. Whenever issues of paternity arise, there is emotional and legal turmoil, and the combination of criminal populations, genetic testing and the stigma surrounding murder, infanticide in particular, children and what some might mistake as eugenics-tinged sociobiology would prevent ethics boards from allowing this work."

"All too easily, the public could descry this kind of study as focused on explaining away incredibly heinous crimes with biological science, of targeting a certain race, income or education level or most broadly of trying to determine who has access to children, mistakenly emphasizing the danger of a stepparent rather than focusing on the protective nature of a related parent," she notes. "And no one wants to revisit biologically-based arguments on who should and should not have or have access to children."


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