"[T]here is no documentary proof that any particular "Boston marriage" included sexual relations. In general, the amount of historical and social scientific knowledge of this phenomenon, and even of the currency of the term at the turn of the 20th century, is scant."
Travis didn't mention anything about "prior to the 20th century" in the post to which you are replying. That said...
According to Wikipedia, there were several societies that practiced same-sex unions, including Ancient Greece and Rome, certain regions of China, and at various times in ancient Europe.
It is believed that a same-sex union was a socially recognized institution at times in Ancient Greece and Rome,[2] some regions of China, such as Fujian province, and at certain times in ancient European history.[3] These gay unions continued until Christianity became the official religion of the Roman Empire. A law in the Theodosian Code (C. Th. 9.7.3) was issued in 342 AD by the Christian emperors Constantius II and Constans, which prohibited same-sex marriage in ancient Rome and ordered that those who were so married were to be executed.
So I guess it was Christianity that perverted the traditional meaning of marriage.
The Greek example is pederasty, wherein an adult male would use an adolescent boy for sex while in the military. This would be unacceptable today, and as explained in the article, was a relationship that would supplant traditional marriage.
Still, the Roman example is revealing. It's interesting to think of ancient cultures that were more socially progressive than ours, at least in some ways.
Why are the laws and mores prior to the 20th Century what defines "normal"?
They don't. However, the claim was that other cultures throughout history had regarded same-sex unions as marriage or socially acceptable. This was news to me, so I asked for proof.
? What is it with anti-gay activists and their sick fascination with this activity?