A quarter-century ago, 65 percent of Americans thought interracial marriage was unacceptable for themselves or for other people.
Yet in the span of a generation, as intermarriage has become more common and the United States has grown more racially diverse, a dramatic change in attitudes has taken place.
Today, according to a recent study by the Pew Research Center, 87 percent of Americans say that the rise in interracial marriage has either been good for society or made no difference, while only 11 percent think it's a change for the worse.
That's the thing about the tide of history: It tends to flow from intolerance to acceptance.
The same shift that occurred in opinions about interracial marriage is happening in attitudes about same-sex marriage. Just ask folks in Washington and New Jersey.
Washington Gov. Chris Gregoire signed a bill legalizing same-sex marriage on Monday, and on Thursday the New Jersey Assembly approved a similar measure.
Voters in those states will probably have the final say; opponents are organizing a petition drive for a Washington ballot measure to ban gay marriage, and New Jersey Gov. Chris Christie has vowed to veto his state's marriage bill and present the issue as a referendum instead.
There's no telling what voters in either state will decide, but such occasional shoals matter less than the overall direction of the tide, and we know which way that's turning.
Surveys show a major generational divide in attitudes about gay marriage, with younger people widely favoring it while older people are generally opposed. As time passes, there's only one direction this trend can lead.
And it's the same direction this country charted during the civil rights era, when anti-miscegenation laws were overturned amid a raucous outcry from conservatives who feared that interracial marriage would unravel our social fabric.
Through surveys like Pew's, we also know what will happen in the decades that follow the widespread legalization of same-sex marriage: An issue that divides Americans as intensely as any in our ongoing culture wars will simply cease to matter, as conservatives discover their own marriages are in no way devalued.
Today, according to Pew, 63 percent of Americans say they "would be fine" if a family member opted to marry someone outside his or her racial or ethnic group, and the overall percentage of interracial marriages is soaring: It hit 15.1 percent nationwide in 2010 and is even higher in California, where the majority of such unions are between whites and Latinos.
Someday, we suspect, most Americans won't be bothered by the prospect of their sons or daughters marrying someone of the same sex.
All it takes is time, and enough examples to demonstrate that the fears of marriage-equality opponents are baseless.