His son can't get the son's wife pregnant and so dad is going to do the job.
A 72-year-old man is due to become the father of his own "grandchild" by acting as a sperm donor for his daughter-in-law. The case is thought to be the first of its kind in the UK. The government's fertility watchdog said there was a "handful" of men over 65 on the sperm register, but some fertility experts are worried that the couple are being subjected to undue risks because the sperm is likely to have many genetic mutations accumulated during the donor's life.
Yes, there are greater risks of genetically caused disease as sperm get older. But there's another more interesting angle here: This isn't genetically incestuous since he's knocking up his daughter-in-law. But a man was going to donate sperm to his daughter. There's a big taboo against that for a couple of reasons, most obviously because recessive harmful genes are more likely to pair up and cause genetic diseases when closely related people mate.
But imagine that a brother and sister or father and daughter used genetic testing combined with in vitro fertilization to select fertilized eggs (i.e. embryos) that do not have have harmful recessive gene pairings. The resulting child won't suffer from the genetic effects of very genetically close mating. Would you think that laws against incestuous mating should still be enforced against such pairings?
Genetically safe mating of closely related people is still a hypothetical case today. But that won't always be the case. Given the rate of advance in genetic testing technologies and the accumulating evidence on the significance of human genetic differences I expect within 20 years time if not sooner we'll know enough to avoid harmful recessive pairings. At that point should incestuous mating between consenting adults remain illegal?
There's a sociobiological argument against genetically very close mating: the mating creates tribal and family divisions in society and reduces what some political scientists call "social capital". I think genetic engineering is going to create divisions between groups of humans more severe than even the existing tribal divisions that are at least partially genetic in origin.
By Randall Parker at 2007 October 06 10:08 AM Bioethics Reproduction | TrackBackTMI
I wonder if double recessives are the only problem. Suppose bacteria and parasites evolve (with much shorter lifespans than humans have) to do better and better against a certain phenotype. This may sound speculative, but some say it's one of the reasons sexual reproduction evolved.
Divisions are good. They mean specialization, and that, in turn, means increased efficiency of division of labor. The more diverse (not "melting-pot" pseudo-diverse) humanity is, the better.
Heinlein (in "time enough for love") suggested future society will redefine "incest" in terms of recessive genes, not heredity.
averros: it's true that diversity is good, but there's no need to limit ourselves to ancestral genes. Cosmetic and functional genetic engineering of human babies can pump more diversity into our species in one generation than natural selection could in a thousand years.
Diversity as such, in this usage, means mutations. If one wants to generate new human genetic diversity, that is very easy, but also against our sound rules on radiation or other mutagens being applied to the germline cells. The statement 'diversity is good', in this context, is much more questionable than one would think from all the mindless government-funded celebrations of diversity.
Suppose that there were donors of germline cells who had already been tapped for incestuous, that is, if half-siblings qualified for this opprobrium or taboo, conceptions, and such that their specific recessive deleterious had shown up. Suppose that they were half-siblings from a donor and had never met, it's not clear that the law would go pro-active to prevent this. It could be that this has already happened since some sperm donors have had thousands of children, and hundreds is not exceedingly rare. There may already be lineages of high quality which have inadvertently been put to this hard test, so that one could screen and get zygotes free of the defects specific to the lineage. That would be like cloning or close to it, and is feasible with today's technology. The point being that there are common defects which might be much more common with inbreeding, and there are those specific to the lineage.