Paternal mutations:
In the story of Sodom and Gomorrah, Lot escapes with two daughters and lives in a cave. The daughters manage to have sex with him and found two nations.
Without getting specific about the biblical cities it is quite clear that a lot of cities have vanished over the years. Some must have vanished simply because they were cities and failed because of urban infertility. Archeological digs have suggested the Sodom, the largest of the cities, has been found and that the population may have been as low as 600. (http://www.accuracyingenesis.com/sodom.html)
That is fairly close to the upper limits of how big a human population could survive long term. If fertility gets into serious decline at 6th cousin, then given a population of 256 so that the maximum distance is 7th cousin, the average distance would be 6th cousin. But fertility does not fall linearly. Couples rather closer than 6th cousin gain fertility faster than those who are more distant than 6th cousin lose fertility. And mating is not likely to be absolutely random. So a viable population of 600 is no stretch, and the destruction would not necessarily have anything to do with fertility. And that goes along nicely with the archeological findings, which do include evidence for a fiery catastrophe.
But the nature of the recovery is of interest. It is women having babies by an older man. That no doubt has happened many times. A population that had been reduced by infertility, might use the same strategy. The reason it might work would be that infertility accumulates over several generations. The young women would be expected to have the fertility of their peers but the older man or men would be expected to have the fertility of a generation before. It just might work.
That brings up a number of issues of course. With the Lot family, one must contend with the question of incest. That would not necessarily be an issue every time. And of course there are all sorts of questions of how the geezers are going to be able to provide for young families, pass on the culture of the community, defend against raiders and so forth.
To this rogues gallery of difficulties must be added another. Old men carry more genetic mutations than young men. (Father Figures, ECONOMIST vol. 404 no. 8799 August 25, 2012 page 64) Most mutations of course have no significant impact, but those that do generally have a negative impact. Sure, there are a few that are improvements, but they are quite rare.
But this is not the end of the world. True genetic diseases are rare and true new genetic mutations appearing in any one generation are rare indeed. Even if the old man has a significantly higher chance of a deleterious mutation than a young man would, it is a small chance, particularly compared with the disaster of having an insufficient number or babies.
So it’s perhaps a word of caution, but in itself it does not rule out the possibility that this strategy, get the older men into action, has something to offer.
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