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Kissin' Cousins!

The Truth About Intermarriage Between Relatives

To set the proper mood for this piece, I think you should first click HERE and listen to this song. Click HERE to read the lyrics.

People always speak in whispers and nervous giggles when it comes to the subject of blood relations and marriage. Of course, a sense of humor is a good thing, but such talk usually conjures up the stereotypical image of a cross-eyed Hillbilly with an incurable disease. I have always hated this stereotype and I know you have too. However, not being one to shy away from any subject, especially a controversial one, I did some looking around and found a couple of very interesting articles I'd like to share with you.


By Duane F. Alwin dfa@umich.edu [Duane F. Alwin is Professor of Sociology at the University of Michigan, where he teaches social psychology, the family and research methods. In his spare time he actively pursues the history of his own family.]

The word "cousin" has a variety of meanings, some of which are more precise than others. We often use the word in a general way to refer to any collaterally related persons more distant than siblings who share a common ancestor. When we want to be more specific, we use the term in a different way: cousins (or first cousins) are the children of siblings. That is to say, the children of my aunts and uncles are my first cousins.

Second cousins, on the other hand, are the children of first cousins, and third cousins are the children of second cousins, and so on. In other words, my second cousins are the children of my parents' first cousins, and my third cousins are the grandchildren of my grandparents' first cousins.

The degree of cousinness, thus, simply follows generational lines, given kinship relations defined by a common ancestor. By contrast,when one crosses generational lines to express relationships among cousins in an adjacent generation or across several generations, one normally expresses these cousin relations as "once removed" or"twice removed" according to how many generations separate the related individuals. Thus, one is a first cousin once removed (1C1R) to his or her parents' first cousins, or to the children of his or her first cousins.

I have always gotten a kick out of telling people that I am a cousin to myself. My maternal grandparents were first cousins once removed-- my grandfather married the daughter of his first cousin. His cousin was 15 years his senior and he was a few years older than my grandmother. In any event, following the above definitions - second cousins are the children of first cousins -- we can see what may appear to be a contradiction. Because they are both daughters of first cousins, my mother is a second cousin to her own mother. This makes me a third cousin to my mother, as she and I are both children of second cousins in the same ancestral lineage. And, of course, to myself I am a third cousin, once removed (3C1R). Thus, when I use my genealogy software to print out the descendants of Samuel CHACEY (our common ancestor) I appear twice (and in different generations) -- once as a descendant of my grandfather and once in my grandmother's line. What better proof that I am my own cousin.

Matings between cousins are called consanguineal, meaning that the members of the pair have one or more common ancestors. In some geographical areas at some times such matings can be quite common. Whether we know it or not, each of us probably has some consanguineous marriage in their pedigree. Most cultures have rules that regulate the degree of relationship permitted between two individuals who wish to marry.

In many societies, including our own, marriages between first cousins, uncles and nieces, and aunts and nephews, are typically discouraged, or in some cases outlawed. Although it would mean fewer grandparents to keep track of, such matings are probably not a good thing. Individuals with rare recessive sex-linked traits are often the offspring of such matings. On the other hand, such consanguineous matings are not necessarily undesirable. Charles Darwin married his first cousin Emma Wedgwood, and the entire Darwin-Wedgwood lineage was highly inbred. Some have speculated that the pre-eminence of this lineage in the arts, sciences, and the professions may have resulted from some inbred genetic trait. But this is probably the exception, and genetic diversity in families is probably healthier over the long run.

It should be noted that 'close marriages' did not originate in the hills of Kentucky and Arkansas. Such matings were very common among royalty all over the world. But now, to get to the hard science of the matter, the following is from Dr. Richard C. Gethmann, a noted biologist from the University of Chicago.

The common argument against intermarriage is that it increases the risk of having a child with a genetic disease. Just how serious is this risk?

First of all, a little background information. Most people have two copies of each of their genes. Genes can exist in alternate forms, called alleles, and it is some of these defective alleles that causes various genetic diseases, such as cystic fibrosis, sickle cell anemia, Tay-Sachs disease and PKU, just to name a few. For a person to have any of these diseases, both of their genes alleles must be the defective disease causing allele. A person who has one disease causing allele and one normal allele will not have the disease. These people are called carriers.

Thus, for a person to have one of these genetic disease, both parents must be a carrier. The risk due to intermarriages is that it increases the risk of BOTH parents carrying one of these defective alleles, which they both inherit from one of their common ancestors.

Now, how great is the risk? That depends on two conditions (1) how common that particular disease is, and (2) how closely related the two people are. In general, the more closely related the people are, the greater the risk.

For example, cystic fibrosis is one the most common genetic diseases. The frequency is 1/2500 live births. The chances that two unrelated persons are both carriers is about 1/625.

But what happens if they are related to each other? Consider the following: A parent transmits to their offspring one of the two copies they have of each gene. If one of the parents is a carrier, then the chances are 1/2 that their children will also be carriers. Given that cystic fibrosis is a relatively common genetic disease, it works out that the chances that two siblings will both be carriers of cystic fibrosis is 1/50, as compared to 1/625 for two unrelated persons. For first cousins, the risk is 1/200 and for second cousins, the risk is the same as if they were unrelated.

PKU is a rarer genetic disease that if untreated, will cause severe mental retardation. The occurrence is 1/12000 live births. The chances that two unrelated people are carriers is 1/2500. For two siblings, the risk 1/100, for first cousins, it is 1/400 and for second cousins, it is 1/1600.

Thus, the real risk is with brother-sister marriages, and to a lesser extent, first cousin marriages. Any relations beyond these are essentially at the same risk as the general population.

Finally, it should be pointed out that intermarriages can also increase the occurrence of desirable traits too. One of the major figures in the 20th century development of population genetics and evolutionary theory, and the person who developed the formulas for studying inbreeding and intermarriages, was himself the product of a first cousin marriage. His name was Sewell Wright and he died in 1988 during a hip operation at the age of 99.

Now here's an interesting bit of triva: I'm my own fifth cousin once removed!! Like Mr. Alwin above, my genealogy program has a 'relationship calculator' that shows this. In fact, almost everyone in our family tree is a cousin of some kind to everyone else because we all had at least one common ancestor. That ancestor was George 'Of All' Sizemore. There is at least one first cousin pairing and several second cousin get togethers. In fact, Lucy Sizemore, a descendant of George, slipped into my fathers family (Adams) and so my father is my mothers fourth cousin once removed. Now that's keeping it in the family!

Don't get me wrong, I am NOT saying that we should all go out and marry a first cousin. What I'm saying is that we can let go of that tiny fear that we have somehow sinned and brought down a plaque on all our houses. We have NOT hurt ourselves, or blood is NOT tainted, and the ignorant ones turn out to be the ones who make the jokes.

-- Skip Adams

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