This switch in cousin-marriage’s acceptance began in earnest in some parts of the Western world in the mid-19th century. Natural Selection himself, was married to his first cousin Emma Wedgwood.
Specifically, until the 1860s or so, first cousins commonly married in Europe and the U. Nonetheless, the practice soon fell out of fashion in the United States.
The stigma attached to first-cousin marriages was supported by early studies into human genetics suggesting that "recessive" versions of a gene (which are not expressed unless there are two of them, one from each parent) are more likely to be expressed in the children of genetically related parents, as well as more likely to be defective.
Most states in America have either outlawed or restricted the practice, as has China, Taiwan and both North and South Korea.
In fact, about 20 percent of marriages, or one in five worldwide is between cousins, according to the Huffington Post.
So let's examine the myths and facts about cousin marriages.
Such legislation reflects outmoded prejudices about immigrants and the rural poor and relies on over-simplified views of heredity.Now a study by the National Society of Genetic Counselors says that having a child with your first cousin raises the risk of a significant birth defect from about 3-to-4 percent to about 4-to-7 percent.According to the authors, that difference isn't big enough to justify genetic testing of cousin couples, much less bans on cousin marriage."Women over the age of 40 have a similar risk of having children with birth defects and no one is suggesting they should be prevented from reproducing," said Professor Spencer, whose co-authored study is published in the online journal Public Library of Science.First-cousin marriages were once quite common in Europe, especially among the elite – Charles Darwin married his first cousin Emma Wedgwood – but that changed in the late 19th-century as people, especially women, became more socially mobile and the risks became more evident.