The American Academy of Pediatrics (AAP) released a policy statement yesterday indicating its support for same-sex marriage. Based on “extensive research,” this statement from a scientific organization may seem authoritative. In reality, however, the AAP’s position is based on ideology, not science.

The AAP claims that children “receive similar parenting whether they are raised by parents of the same or different genders.” But this is far from clear from the existing literature. Much of the research on outcomes for children in same-sex versus heterosexual households lacks the ability to confidently rule out the possibility of differences when comparing averages among the broader population.

In particular, the main challenge to research on the children of parents in same-sex relationships has been simply finding enough of them to analyze in the first place. Small sample sizes, inadequate (or even non-existent) comparison groups, and narrow sets of outcome measures have been endemic in the literature on same-sex parenting. Recent studies aimed at addressing these shortcomings have tended to suggest—but certainly not prove, at this point—that there could be disadvantages associated with having had a parent in a same-sex relationship.

But the bottom line is that the literature on same-sex parenting is not conclusive enough to generate any policy prescriptions from social science alone. We just don’t know nearly as much as the AAP claims that we know.

So why would the AAP endorse same-sex marriage? As a terrific legal brief by scholars Harvey Mansfield and Leon Kass reminds us, it is not unusual for science to be influenced by politics. Scientists are people, too, with the same kind of political beliefs and biases that everyone exhibits to one degree or another. It’s natural for people with a strong ideological predisposition to want the science to match their beliefs.

In fact, the AAP has a long track record of using its air of scientific authority to make pronouncements on ideological issues. For example, the organization recently issued a “call to action” to ban certain types of guns and ammunition clips. It praised Obamacare’s “historic investment” in Medicaid expansion. The AAP even adopted the Obama Administration’s budgetary talking points in arguing for “a balanced approach to deficit reduction.”

These are perfectly legitimate political positions, but they are not scientific positions. We should never confuse the two, especially not when dealing with an issue as important as the definition of marriage.