Go Ahead, Kiss Your Cousin

In 2003 Discover Magazine had an article about cousin marriage:

In the United States they are deemed such a threat to mental health that 31 states have outlawed first-cousin marriages. This phobia is distinctly American, a heritage of early evolutionists with misguided notions about the upward march of human societies. Their fear was that cousin marriages would cause us to breed our way back to frontier savagery—or worse. "You can't marry your first cousin," a character declares in the 1982 play Brighton Beach Memoirs. "You get babies with nine heads." So when a team of scientists led by Robin L. Bennett, a genetic counselor at the University of Washington and the president of the National Society of Genetic Counselors, announced that cousin marriages are not significantly riskier than any other marriage, it made the front page of The New York Times. The study, published in the Journal of Genetic Counseling last year, determined that children of first cousins face about a 2 to 3 percent higher risk of birth defects than the population at large. To put it another way, first-cousin marriages entail roughly the same increased risk of abnormality that a woman undertakes when she gives birth at 41 rather than at 30. Banning cousin marriages makes about as much sense, critics argue, as trying to ban childbearing by older women. But the nature of cousin marriage is far more surprising than recent publicity has suggested. A closer look reveals that moderate inbreeding has always been the rule, not the exception, for humans. Inbreeding is also commonplace in the natural world, and contrary to our expectations, some biologists argue that this can be a very good thing. It depends in part on the degree of inbreeding.

Why Marrying Your Cousin May Pay Off

In 2014 Live Science had an article about cousin marriage:

Yet some research suggests an alternative perspective. "There's this counterintuitive finding that higher spousal relatedness is related to higher reproductive success in several humans societies," said Drew Bailey, a psychologist at Carnegie Mellon University in Pittsburgh, and co-author of the study detailed May 21 in the journal Biology Letters.

Even in modern, industrialized society, research suggests that people tend to marry others with similar DNA.

In line with previous findings, the researchers found that among non-foraging societies, a couple's relatedness was linked with having more surviving children. But among foraging societies, the opposite was true: More-closely related spouses had fewer surviving children.

Furthermore, the more family intermarriage in a society, the greater the benefit of intermarrying on the number of children couples had. In other words, in societies in which people frequently married their relatives, intermarrying showed a stronger link to having more children.

There could be many explanations for the different effects of inbreeding shown in the two kinds of societies. Perhaps the best explanation, Bailey said, may be that non-foraging societies are more likely to have heritable resources, such as wealth or livestock, so a tight-knit family group might be more likely to defend each other and their shared resources. By contrast, in a foraging society, it might make more sense to be part of a much larger, interconnected group, since there are few or no resources to be inherited.

When Cousins Get Married

In 2006 ABC News had an article about cousin marriage:

Everyone wants to fall in love.

It's the stuff of movies, songs and dreams.

But what if you fall in love with your cousin?

For two cousins, romance bloomed when they met as adults after a 20-year absence.

"We ran into each other, at a family reunion," Christie Smith said. "And we just struck it off."

Smith said marrying her cousin, Mark, brought concerns.

"It was very scary, at first. I thought that it was something that was very wrong," she said.

Cousins who fall in love have a right to voice concerns. After all, marrying a cousin just isn't done, right?

Keeping Marriage in the Family

The Oprah website has an article about cousin marriage:

Most people balk at the idea of first cousins marrying each other, but the practice isn't as forbidden or as risky as you may think.

In other parts of the world, marrying your first cousin is socially acceptable; in the United States, it's a bit more taboo. But in 21 states, it is legal for first cousins to get married, according to the National Conference of State Legislatures' website (NCSL). Professor Alan Bittles of Murdoch University and Edith Cowan University in Australia has studied cousin marriages for the past 30 years. He says it's likely 10.4 percent of people worldwide are married to a close relative or are the children of such a marriage. "This equates to over 700 million people," Bittles says.

The assumption that children of first cousins are likely to suffer from health problems has been around for centuries, Bittles says. "Although there has been a tradition of cousin marriage among royalty, major land-owning families and some business dynasties, the highest rates of consanguinity [cousin marriage] are actually among the rural poor whose general health status often is marginal," he says. "Under these circumstances, unless appropriate allowance is made for adverse family socioeconomics, just about all health problems have simply been blamed on consanguinity, even though there usually is no specific evidence of a causal relationship between consanguinity and the disorder in question."