Bible Trivia - 3/4/2008

Question:What did Rebekah and Tamar have in common in respect to childbirth?

Answer: Both had twins (Genesis 25:24-26; 38:27-30).

Comments: Rebekah gives birth to the first set of twins in the Bible, fraternal twin brothers Isaac and Esau. Her grandson Judah also has twins as the result of an illicit affair with Tamar.

On the surface, Rebekah and Tamar support the conventional wisdom that twins not only run in families, but they also skip a generation. Though this claim is often taken as common knowledge, it is not entirely true.

There is a gene that can predispose women to hyperovulation, or the releasing two or more eggs in a single menstrual cycle. When both eggs are fertilized, the resulting siblings are fraternal twins. Because this gene is hereditary, the tendency to have fraternal twins can run in families. This is not the case with identical twins, as this occurs randomly when one fertilized egg splits.

The assumption that twins always skip a generation is a myth. The illusion may have arisen because men who inherit the gene from their mothers are unaffected by it (clearly, they do not ovulate), but can still pass it on to their daughters, who, in turn, will have an increased likelihood of conceiving twins. Thus, twins can run in families, but do not necessarily bypass generations.

Source: The New York Times, 10/2/2007.