Who did Cain marry? (continued)
In most societies around the world, there are consanguinity laws which forbid intermarriage among close relatives. Our instinct, therefore, is to react negatively at the thought of a man marrying his own sister.
Countries have instituted consanguinity laws because the children of closely related parents are more likely to have genetic defects. Why is that so? The reason is that the human race is subject to a phenomenon that has been termed “genetic entropy.[i]” Simply put, each successive generation has a slightly increased level of harmful mutations in its genetic code—minor imperfections arise in the intricate copying of the genetic code from one generation to the next. Those imperfections are much more likely to find expression (such as congenital deformities) when two closely related people marry and carry the same imperfections in their genes. When distantly related people marry, the genetic code imperfections are carried on in recessive genes that do not appear in their offspring. These imperfections do remain part of the increasingly corrupted genetic make-up of their offspring.
At the beginning of the human family, there was no damaged genetic code. Only over time, as genes were copied tens of times across human generations, have genetic “mistakes” gradually accumulated. As a result, congenital deformities were not a risk in the early generations of the human race by marriage between closely related husbands and wives. Even as late as the time of Abraham, about two thousand years after the creation of Adam and Eve, it was socially acceptable for Abraham to marry his own half-sister, Sarah. Abraham and Sarah had the same father but different mothers. “Besides, she is indeed my sister, the daughter of my father though not the daughter of my mother, and she became my wife” (Genesis 20:12).
The steady accumulation of genetic copying mistakes in each successive generation—the inevitable result of genetic entropy at work—bears witness to two remarkable conclusions:
Human beings did not evolve over hundreds of thousands of years from simian ancestors–our genetic code would have been much more badly corrupted with flaws than it is; replication of the genetic code always tends in a degenerative direction, not in a progressive one. Thus our ancestors were endowed genetically at the beginning by God with a perfect genetic arrangement.
2. The human race has not been on the earth for more than a few thousand years—its age must be consistent with the estimated rate of accumulation of genetic decay over successive generations.
[i] For further explanation, refer to https://www.geneticentropy.org/whats-genetic-entropy