A group of social science professors present the scholarly research on a child’s need for a married mother and a father in a brief submitted to the Supreme Court.

The brief demonstrates that when it comes to same-sex parenting, we do not have adequate studies. The phenomenon is too new and the instances too few for it to be reliably—let alone conclusively—studied. Recent studies claiming that children raised in same-sex homes are “no different” from those raised in traditional homes are seriously flawed:

[T]he vast majority of [these] studies were based on samples of fewer than 100 parents (or children), and typically representative only of well-educated, white women (parents), often with elevated incomes. These are hardly representative samples of the lesbian and gay population raising children, and therefore not a sufficient basis to make broad claims about child outcomes of same-sex parenting structures.

This faulty methodology lends itself to mistaken conclusions showing no differences between groups. However, studies using larger sample sizes and more robust methods have cast the “no difference” thesis into doubt.

A recent study, using a large random population-based sample, shows that children raised by married moms and dads did far better in education and employment than peers in other parenting arrangements—including same-sex relationships—and were less likely to suffer from depression and drug use. They were less likely to be sexually abused, receive welfare, have an affair, or cohabitate.

What we do know, reliably and conclusively, is that married biological moms and dads matter to children. As the brief states:

It is not simply the presence of two parents…but the presence of two biological parents that seems to support children’s development.… Experts have long contended that both mothers and fathers make unique contributions to parenting.

The professors present a great deal of scholarship showing that mothering and fathering are different. The mother plays a critical role in a child’s neural development, communication, sense of security, problem solving, understanding and responding to feelings, and social ties to both friends and family.

The father’s involvement is linked to positive outcomes in education, physical health, and avoidance of juvenile delinquency. Children who “roughhouse with their fathers” learn that certain violent behavior is unacceptable. Fathers encourage exploration and discourage boys from “compensatory masculinity where they reject and denigrate all that is feminine and instead…engag[e] in domineering and violent behavior.”

Even President Obama himself emphatically stated that children need fathers to keep them in school, out of poverty, and out of prison. President Obama concluded by lamenting that “the foundations of our community are weaker because” it lacks involved fathers.

But redefining marriage denies the importance of mothers and fathers, and same-sex parenting arrangements, as the professors point out, “by definition, exclude either a mother or a father.” The concern is not whether same-sex couples can make “quality and successful efforts in raising children.” It is that there “remain unique advantages to a parenting structure consisting of both a mother and a father, political interests not withstanding.”

Marriage is, as the scholars write, “a liberty to be accorded to children…as much as to their parents.” As such, the definition of marriage should promote “what is known to be an ideal environment for raising children.”

Kayla Griesemer is currently a member of the Young Leaders Program at The Heritage Foundation. For more information on interning at Heritage, please click here.