Politicized science from the American Anthropological Association

The AAA shows a hitherto unsuspected interest in the Constitution of the United States:

"The results of more than a century of anthropological research on households, kinship relationships, and families, across cultures and through time, provide no support whatsoever for the view that either civilization or viable social orders depend upon marriage as an exclusively heterosexual institution. Rather, anthropological research supports the conclusion that a vast array of family types, including families built upon same-sex partnerships, can contribute to stable and humane societies.

The Executive Board of the American Anthropological Association strongly opposes a constitutional amendment limiting marriage to heterosexual couples."

You know, Samoans are probably still laughing at Margaret Mead, and but let's assume that these people know what they're talking about this time and aren't addled by liberal politics. Why did they phrase their statement as they did?

In particular, is there any evidence that gay marriage will *not* harm societies? Is there any evidence that gay marriage will be beneficial to a society?

Don't cry to me about proving a negative. It's too bad if they have a hard time answering these questions - they're fair, obvious and relevant. If the AAA didn't want to have to deal with them they should have kept their mouths shut.