Caribbean Consanguinity


The president of our technology company is also a commentator. He is writing a book on the various conditions of this country including social conditions. One of his areas of interest, is consanguinity. Consanguinity is the property of inter-relatedness, or put simply, two people sharing a common ancestor. On an island with a long history, consanguinity is not only a social issue, but it has socio-economic implications as well.

Social mores, or how people perceive sex and child-bearing is different in the Caribbean than in say the mainland Americans. Taboos are a lot looser, and there appears to be no social stigma to having children out of wedlock.

Some of the background information presented here comes directly from hospital records. In this island nation, there are about 5,000 births per year. Twelve percent, or 600 hundred of these births are to girls under the age of 16. Three thousand of these births are to single women. Of these three thousand, over 1,200 women already have a child by a different father than the child that they are giving birth to.

I conducted an online survey related to consanguinity on the local forums. I will post some of the more interesting results as I finish the calculations.

One of the questions that I asked was:

"How many men in your circle of acquaintances have fathered a child with more than one woman".

The results were astonishing. The mean average was 6. Among the respondents, most people knew an average of six men who had fathered a child with more than one woman.

The median average was 8. That means that half the respondents knew less than 8 men with children by more than one woman, and the other half of the respondents knew more than 8 men with children with more than one mother.

The modal average is split evenly between two and ten. A modal number is one that appears most often. From that I can make an inference that some respondents knew only a couple men with multiple parent partners, and some knew a high number of men with a child by more than one woman. Does this suggest that there is a division of classes of people -- those who have a low number of procreating men with multiple partners, and those that don't? It would be an interesting path to explore for a sociologist.

To get down to the nitty gritty of statistics, the standard deviation is 3.79 spread over this number set. That means that since the respondents knew on average, 6 men who impregnated more than one woman, using the standard deviation, the majority of answers would fall between 2 and 10, which is mirrored exactly in our modal average.

Standard deviation can be used to deduce another fact. It is the "twice the standard deviation rule". 95% of all respondents would fall into the category of knowing twice the standard deviation of men above and below the average. Since the standard deviation is rounded to 4 (you can't have .79 of a person -- although I have known a few of those), the range is from 0 (you can't have -2 people) to 13 men having a child with more than one woman. Let me restate this more clearly.

If you asked all of the islanders, 95% of them would answer that they know between 0 and thirteen men (two standard deviations above and below the mean) who have fathered a child with more than one woman.

It is an amazing statistic, especially at the high end of thirteen. How does this impact consanguinity? I will show in a later blog entry, some more results of my survey, and the conclusion that I have come to. The conclusion is this:

When an islander here marries another islander, there is a 50:50 chance that they will share a common ancestor within the past three generations.

That is some serious stuff.

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