Those who wish to change the historic definition of marriage so as to include couples of the same sex often argue that marriage is a fluid institution with an evolutionary history. One of their favorite examples is polygamy. Polygamy used to be an acceptable form of marriage, but such is no longer the case in most societies. They think it follows that if the definition of marriage is flexible enough to change in this fashion, then it should be capable of including people of the same sex as well.
The problem with this argument is that polygamy is not an exception to the “male and female” understanding of marriage. Rather, it is an exception to the concept of monogamy. Polygamy did not involve multiple partners in a single marriage, but rather multiple, concurrent marriages. This can be demonstrated by the following:
- Each wife entered into a marriage with the man at different points in time.
- It was possible for the man to divorce one wife without divorcing all his wives.
- The women in the relationship only viewed the man as their spouse, not the other women.
Western civilization’s insistence on monogamy has done nothing to change the historic definition of marriage. It has only limited the number of marriages a person can enter into.
Same-sex marriage advocates also sight the evolution of the status of women in marriage as an example of marriage’s evolutionary history. In the past women were viewed as property and often treated poorly, whereas today women are viewed as and treated as equal to men. But this is not an example of the definition of marriage being changed. It’s an example of evolving attitudes toward the female spouse in a marriage. When women were viewed as property marriage involved a man and a woman, and now that women are no longer viewed as property marriage involves a man and a woman. No evolution here.
Finally, same-sex marriage advocates point to anti-miscegenation laws (laws prohibiting marriages of mixed race) as proof of marriage’s evolution. In the past blacks and whites were not allowed to marry, but now they are. A few things need to be noted. First, this is not an evolution to the definition of marriage as one man and one woman. Same-race and mixed-race marriages both involved a single man and single woman. Secondly, race and sex are completely different. Sex, not race, is integral to the concept of marriage because sex is directly related to procreation, which is the reason governments involve themselves in the marriage business in the first place. Thirdly, anti-miscegenation laws were only necessary because it was recognized that mixed-race marriages were legitimate marriages, hence the need to outlaw them. Anti-miscegenation laws were racially motivated laws intended to prevent legitimate—but undesirable—marriages from being formed. This is in stark contrast to same-sex marriage, in which it is the inability of people of the same sex to marry one another that is the cause for anti-same-sex legislation. As Maggie Gallagher writes:
The Supreme Court overturned anti-miscegenation laws because they frustrated the core purpose of marriage in order to sustain a racist legal order. Marriage laws, by contrast, were not invented to express animus toward homosexuals or anyone else. Their purpose is not negative, but positive: They uphold an institution that developed, over thousands of years, in thousands of cultures, to help direct the erotic desires of men and women into a relatively narrow but indispensably fruitful channel. We need men and women to marry and make babies for our society to survive. We have no similar public stake in any other family form–in the union of same-sex couples or the singleness of single moms.
The editors at National Review Online similarly write:
Same-sex marriage is often likened to interracial marriage, which the law once proscribed. But the reason governments refused to recognize (and even criminalized) interracial marriages was not that they did not believe that such marriages were possible; it is that they wanted to discourage them from happening, in the interests of white supremacy. Sexual complementarity is a legitimate condition of marriage because of the institution’s orientation toward children; racial homogeneity has nothing to do with that orientation. Laws against interracial marriage thus violated the right to form an actual marriage in a way that laws defining marriage as the union of a man and a woman do not violate it.
The fact of the matter is that the definition of marriage has always been the same: one man and one woman. Same-sex marriage would not be a minor variation on this theme, but a complete gutting of marriage’s core concept.
 Maggie Gallagher, “What Marriage Is For;” available from http://www.weeklystandard.com/Content/Public/Articles/000/000/002/939pxiqa.asp?pg=2; Internet, accessed 23 December 2003. Originally appeared under the title “Children Need Mothers and Fathers” in the August 4, 2003 issue, Vol. 8, Issue 45, of The Weekly Standard.
 National Review Online editors, “The Case for Marriage”; available from http://www.nationalreview.com/articles/print/245649; Internet; accessed 10 September 2010.