Of all the details that have emerged about the murder of eight-year-old Thomas Valva last month on Long Island—the multiple reports to child protective services by his mother about the abuse he was enduring at the hands of his father; the calls from the child’s school, reporting that he and his brother could not concentrate because they were not being fed at home; and the father making the boy sleep in the garage in below-freezing temperatures, ultimately killing him—the most puzzling may be that a judge awarded father Michael Valva sole custody of his son during his divorce from the boy’s mother a few years ago.

A court’s decision to take Thomas and his two brothers away from their mother, Justyna Zubko-Valva, and place them with their abusive father and his fiancée, Angela Pollina, set the tragedy in motion. The New York Post reported that Nassau County Judge Hope Schwartz Zimmerman made the decision in 2017 “without any formal, court-filed accusation of wrongdoing against their mom, Justyna Zubko-Valva.” According to the Post, “Zimmerman even went so far as to bar Zubko-Valva from any contact with her children—a decision she made after listening to spoken, unsubstantiated complaints from the father’s lawyer and an attorney appointed to represent the boys, both of whom accused the mom of flouting court directives.” New reports suggest that Zubko-Valva insisted that a court-ordered evaluation of her parenting be recorded, and after the evaluator refused to allow taping, Zubko-Valva did not permit the evaluation to take place.

In any case, how a woman who was by all accounts a devoted mother lost the right to any contact with her children is a story that needs some historical context. In the nineteenth century, courts moved from giving custody of children to their fathers after the breakup of a marriage to favoring the mothers, particularly when children were young. As family law expert Martin Guggenheim observes: “Under the ‘tender years’ doctrine, mothers were presumed to be the more capable nurturer of young children and, for that reason, custody of young children (up until the age of ten) was presumptively given to them.” This rule largely held until the 1970s, when the fathers’-rights movement took off and, “adopting the feminist movement’s rhetoric that gender roles were cultural constructs that should no longer be taken seriously, men complained that they were systematically disadvantaged in custody disputes, based on lagging gender stereotyping of women as better nurturers.”

The demise of the “tender-years” doctrine has been a disaster for mothers and children. The default assumption in divorce cases today is to give parents joint custody, even if the father has not spent much time with the children, and even if the father is not their biological father. As Robin Fretwell Wilson, the director of the family law and policy program at the University of Illinois, explains, “there are certain things we can’t say anymore and one of those is that mothers are going to be more invested in their children and protective of them.” This is not to say that fathers don’t protect their children or that we should suspect that they all might be abusers. Rather, as Wilson says, “across large groups we know certain things about mothers and fathers.”

As Wilson points out, the preference for joint custody means that even fathers with no interest in custody can use it “as a bargaining strategy” when negotiating financial settlements for divorce. Since women are “more risk averse” when it comes to getting the kids, she explains, “they will hurt themselves on the property front just to get it.” Further, because courts are now required to treat men and women as equally likely to be good caregivers for young children, the negotiation turns more often on “who presents better.” It’s likely that courts often penalize women like Justyna Zubko-Valva, who don’t have the same financial resources as their partners (she couldn’t afford a lawyer and was representing herself) and who may be under emotional duress.

George Washington University Law School professor Joan Meier suggests that women who suffer domestic violence from their spouses struggle especially under the new assumptions. These women find themselves accused of being “unfriendly parents” when not cooperative with the court or their partner, or of “alienating” the children from their father. In a recent study of 4,388 custody cases between 2005 and 2014, Meier and her colleagues found that, when mothers reported abuse, they lost custody 28 percent of the time. When fathers said that the mothers were abusive, the fathers lost custody only 12 percent of the time.

The current standard of the “best interests of the child” provides lots of wiggle room for judges to award joint custody. Even if the man in question is not the biological father and has been living with the mother for only a short time, he can make a custody claim. Wilson believes that courts should adopt the standard that the child’s “primary caretaker” should become the default custodian in divorce cases, though such a rule might result in claims of unequal protection under the law.

Meantime, though, it’s worth noting the far-reaching and destructive impact on families of the claim that gender is merely a social construct. Until this assumption changes, we will remain obliged to pretend that men and women are the same in all respects—even when we know better, and even when children suffer as a result. This au courant thinking, along with the timeless human capacity for evil, cost young Thomas Valva his life.