Cousin marriages, or the wedding of two individuals related by blood through an earlier generation, is an issue with a surprisingly wide spectrum of controversy and acceptance throughout the world. What was once seen as a sensible solution to strengthening family ties and keeping wealth and power concentrated is now abhorred as obscene in some parts of the world while remaining perfectly unremarkable and acceptable in others. Cousin marriage is less prominent in the 21st century than in earlier times, but still remains an important piece of the global marital picture. According to some estimates, about 10% of marriages in the modern world are between cousins.
Throughout history, cousin marriage has been an important part of maintaining family stability, especially among royal and upper classes. By marrying within the family, couples newly cemented the ties between family groups, ensuring that a profitable relationship continued into the next generation. The duo that launched Columbus, Ferdinand and Isabella of Spain, were second cousins, while the first and sixth wives of the frequently-married King Henry the VIII were also his cousins. Going back even earlier into the tribal days of ancient history, familial marriage, including cousin marriage, served to strengthen bonds in times of war and strife, to ensure a strong clan tied by multiple marriages.
Today, legal criticism of cousin marriage is typically based on two arguments: the possibility for genetic repercussions, and the scope of incest laws. The genetic concern lies in the fact that people related by blood may have a higher chance of possessing identical recessive traits, such as those for certain inherited diseases, birth defects or deformities. If both parents possess a recessive gene, they have a higher chance of passing on the trait to offspring. Some recent studies, however, have shown the instance of genetic issues caused by consanguinity to be only slightly higher than in cases of non-related parents, or about at the same level of risk as women who bear children after age 40. Genetic issues, however, may be more likely to crop up with repeated instances of cousin marriage throughout several generations, such as in the famous case of the European royal family of Hapsburg.
The incestuous or taboo argument is often harder to justify through law, as it is based on moral relativity. Cousin marriage is not only legal but encouraged in some cultures, while in others it is downright banned as not only immoral but also illegal. Even within the United States, serious divisiveness occurs on the topic, with marriage between first cousins legal in 19 states and the District of Columbia, illegal in 26 states, and legal in limited circumstances in the six remaining states.