By Emma Lacey-Bordeaux, CNN
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(CNN) - When the Supreme Court took up the issue of same sex marriage last week, one phrase seemed to be quite popular: "traditional marriage." Two of the Justices spoke about the long history of traditional marriage. For examples, Justice Samuel Alito said:
[0:15] "Traditional marriage has been around for thousands of years, same sex marriage is very new."
It's true that people have wed for centuries but many historians say the kind of marriage recognized by the U.S. government today is not the same as the kind that existed 200 years ago.
Dr. Elizabeth Pleck of the University of Illinois has studied the topic:
[1:05] "Traditional marriage once included the idea of the covered legal status of married women. That is that the husband and the wife were one and the 'one' was the husband."
That concept began to change when the government granted women more rights. First came rights to own property, followed by the right to vote. Both of which are often taken for granted today. At the time though, Dr. Pleck says opponents voiced concerns about how these changes would impact marriage.
Throughout American history marriage has changed in other ways. Notably the 1967 Supreme Court ruling which invalidated laws against miscegenation, or mixing of races. Now around 10 percent of American marriages are interracial.
In an amicus brief submitted in support of the respondents in the DOMA case heard last week, Dr. Pleck and a couple dozen other historians spelled out other changes.
Still, Dr. Pleck says she understands why people worry about changes to marriage. After all, she says, the interest in regulating marriage stems from the belief that marriage stabilizes society as a whole.
Still, she argues, that would not be meaningful to people today if it had not undergone changes in years, and centuries, past.
[3:26] "The institution of marriage is not the same now as it once was and the reason the institution of marriage is so meaningful to people is precisely because it keeps track with and keeps up to date with the times it's not an unchanging institution."