In an excellent Public Discourse essay today, appellate lawyer Gene Schaerr summarizes the central arguments of the amicus brief that one hundred marriage scholars have submitted in the pending Supreme Court cases challenging state marriage laws. As Schaerr explains, the redefinition of marriage to include same-sex couples would

create a substantial risk of reduced heterosexual marriage rates—not because of individual same-sex marriages, but because the institutionalization of same-sex marriage necessarily requires replacing the gendered “man-woman” definition with a genderless “any qualified persons” definition. And that change from a gendered to a genderless understanding would undermine some of the key, secular norms that, among other things, encourage heterosexuals to marry.

Further, the “‘breathtakingly subversive’ metamorphosis” of marriage that SSM proponents celebrate “will not affect all equally”:

It will especially influence heterosexual men, who generally need more encouragement to marry and have children than women. The metamorphosis of marriage from a gendered to a genderless institution conveys to men (and women) that society no longer needs men to bond to women to form well-functioning families or to raise happy, well-adjusted children. And that message is especially likely to be influential among those on the margins: the poor, the relatively uneducated or others who are highly influenced by cultural messages promoting casual or uncommitted sex.
The weakening or destruction of these norms would result in fewer marriages, more procreation out of marriage, and a higher percentage of children raised in a home without both parents—usually without a father. The consequences would be stark and disastrous: more childhood poverty; increased psychological and emotional problems; more teenage pregnancy; poorer performance in school; higher amounts of substance abuse; more youth committing crimes; and more girls undergoing abortions.

To those who think all of this “seems too theoretical,” Schaerr recalls how no-fault divorce likewise “fundamentally altered the institution of marriage” and left massive destruction in its wake:

The divorce culture, which started at the margins, has now penetrated the institution of marriage to its core. And the collapse of marriage among the poor in our inner cities reveals how susceptible the institution is to legal alteration, and how devastating its demise can be for children. Like a fragile ecosystem, the institution of marriage did not spring into being overnight, but it can be irreversibly damaged in a hurry.

According to the marriage scholars, “it is reasonable to predict that, over a generation, a forced redefinition of marriage would produce at least a 5 percent reduction in heterosexual marriage rates” and “would result in an increase of nearly 1.3 million never-married women, and an increase of nearly 600,000 functionally fatherless children” (as well as 900,000 abortions).

(Yes, the marriage scholars also consider the welfare of the relatively tiny number of children being raised by same-sex couples.)