Sunday, August 18, 2013

Genetic risks in cousin marriage


Alice C. Linsley


Abraham's Horite people (the Horim) had a distinctive and unique marriage pattern. The ruler-priest had two wives. The first wife, taken while the man was still young and not yet the ruler, was his half sister, as Sarah was to Abraham. Shortly before the man ascended to rule over his father's territory, he took a second wife who was most often a patrilineal cousin, as was Keturah to Abraham. The two wives lived in separate households, usually on a north-south axis.

Many of the most famous biblical figures are the sons of cousin brides: Lamech the Younger, the father of Noah (Gen. 5); Joktan the Younger, son of Keturah and Abraham's first born son (Gen. 25); Jacob, Isaac's son by his cousin Rebecca (Gen. 25), and Moses' son by his cousin Zipporah (Ex. 2).

The firstborn son of the sister wife ascended to the throne of his biological father. So Isaac ruled over Abraham's territory.  The first born son of the cousin wife did not belong to the household of his biological father. Instead he became a sort of prime minister in the territory of his maternal grandfather, after whom he was named. This is why it is necessary to speak of Lamech "the Elder" and Lamech "the Younger" or Esau "the Elder" and Esau "the Younger." This was the practice of E. A. Speiser in his Anchor Bible Commentary on Genesis.

This pattern of the cousin bride naming her first born son after her father is called the "cousin bride's naming prerogative." This naming practice makes it possible to trace Jesus' Horite ancestry from Genesis 4 and 5 to the New Testament. Jesus is then the fulfillment of Horite expectation.

The question is often raised as to the risk of genetic defects in cousin marriages. Geneticist Dr Eamonn Sheridan, from the University of Leeds, says: "It is important to note that the vast majority of babies born to couples who are blood relatives are absolutely fine, and whilst consanguineous marriage increases the risk of birth defect from 3% to 6%, the absolute risk is still small."

This risk is hardly greater than the risk for birth defects among white women over 34. Here the risk of bearing a child with a defect increases from 2% to 4% for them.

Poverty presents less risk than poor education and lack of information for expectant mothers. Research shows that higher levels of maternal education reduce by half the risk of having a baby with a defect across all ethnic groups.


Horite understanding of reproduction

The ancient Horites had a fairly sophisticated understanding of reproductive mechanisms. We find evidence for this in Jacob's expansion of his herd (Gen. 30) whereby he practiced genetic recombination.

From the biblical evidence it appears that the Horites used a modular formula when selecting marriage partners from among their Horite kin. This is alluded to in the account of Laban's insistence that the older sister (Leah) must marry before the younger (Rachel). 

The deliberation about marriage partners likely involved a cycle of between 9 and 12 choices. In this equation X represents firstborn son, and the possible matches are between 9 and 12 blood related females, but they must be considered in a fixed order of rotation. There will never be a 13th possibility.

A bride must be selected from the 9-12 females and may be either a half-sister or a cousin, usually patrilineal, but sometimes matrilineal. The bride for the next son will be considered in the rotation, beginning with the next female in the rotation after the last match was made. Marriages were arranged.

The number 9 is based on the evidence that Abraham's ancestors were organized in groups of 3 clans and there were 3 groups of 3 clans, which means that there were 9 clans from which a consanguine bride could be chosen. The number 12 is based on the evidence of numerous 12 tribe sets, with celestial animal totems organized on the 12 moon phases.


1 comment:

Alice Linsley said...

As a side note, there is greater risks in first cousin marriage which is more common these days among Muslim populations than Jewish. The Jews have inter-married with non-Jews more than the Arab populations have.