You support gay marriage, so you must be gay, right? A person asking this question would be laughed out of most conversations. Nonetheless, I've often been asked a very similar question whenever I discuss another facet of marriage equality incest. Even jokingly, if I take a devil's advocate position of legalizing incest, the conversation becomes hushed, and people begin wondering if I'm dating my cousin. However, incest is a serious issue, and the most commonly cited reason for banning incestuous marriages that children born to incestuous parents have a significantly increased risk of genetic mutations does not hold up to empirical scrutiny.
First, even if genetic mutations were a serious issue, there is no guarantee that an incestuous couple will even have babies. What if the couple is in a gay relationship? What if the man has a vasectomy? What if the couple signs a contract foregoing parenthood? Many couples are sterile. What if they adopt instead? These are questions that most conversations surrounding incest simply ignore.
Second, how probable are genetic mutations due to incest? Washington University medicine professor Robin Bennett and his colleagues published an article titled "Genetic Counseling and Screening of Consanguineous Couples and Their Offspring" in the Journal of Genetic Counseling on this very topic. They explain that cousin relationships are "not infrequent in the United States and Canada, and these are preferred marriages in many parts of the world." The article states that the offspring of first cousin unions have an approximately 1.7 to 2.8 percent increased risk for genetic defects above the general population's risk of 3 to 4 percent. At what point does the government have a compelling interest to intervene in the private lives of citizens to govern marriage? Is 2.8 percent a significant enough threshold to warrant such an intervention?
If prohibition and the war on drugs have proven anything, it is that making an act illegal does not necessarily prevent people from engaging in it. By nearly all estimates, legalizing incest would not increase the number of incestuous marriages by much. Would you be compelled to marry your sibling simply because it is legal? Instead, the ban forces incestuous couples into the closet and prevents them from seeking medical advice or attention for children they plan to have or have already had. Screening is the single most effective solution to genetic problems. By thoroughly examining a family history, the doctor and the parents involved could assess the risk in order to make responsible decisions. However, since incest is illegal, social stigma causes a chilling effect that prevents that conversation from ever taking place.
Even worse, the Center for Disease Control and Prevention publicly acknowledges that it does not know the cause for over 70 percent of all genetic birth defects, and even for the known ones, it becomes extremely difficult to pinpoint an exact cause. Numerous environmental factors, parental health and family histories all make proving causality a nearly impossible task. If a 2.8 percent increase in the risk of birth defects warrants a ban on marriage, where do we draw the line? The sickle cell trait affects one in 12 African-Americans. Furthermore, one in 25 Ashkenazic Jews have the Tay-Sachs gene. Should we stop Ashkenazic Jews and African-Americans from marrying? Furthermore, if we are really so concerned about our children, why is it legal to smoke and drink alcohol while pregnant?
Perhaps the greatest evidence that the laws are not really concerned with genetics is the fact that states do not discriminate between "biological kin" and "married kin." In most states, marrying a step-brother is no different than marrying your actual brother. Very reputable sources have informed me that you do not inherit genes from step-siblings, who, by definition, have two different biological parents than you do. Furthermore, as Bennett put it, "prohibition against cousin marriages are not based on empirical biological research or genetic theory."
Incest is a complicated issue. It's one on which I have not yet reached a decision, and there are many good arguments, such as potential for abuse and unequal power dynamics, for why incestuous relations should not be condoned. However, a 2.8 percent increase in the risk of a genetic mutation is not one of them. Incest makes you feel icky, and you'd rather not consider it. I get that. But instead of just putting it away in that box of "gross" things, let's dig a little deeper.
