Midwives have been told about the benefits of “close relative marriage” in training documents that minimise the risks to couples’ children.
The documents claim “85 to 90 per cent of cousin couples do not have affected children” and warn staff that “close relative marriage is often stigmatised in England”, adding claims that “the associated genetic risks have been exaggerated”.
Lots of things lead to increased risk of birth defects, like having children after the age of 30. I thought it was pretty well known that the risks associated with inbreeding drops off pretty sharply at the cousin level? At that point I think the appropriate reaction is social stigma, but not legal ramifications.
It also compounds over generations; if you’re the child of first cousins, you really should seek someone who it would take genealogy research to find a common ancestor with. If you’re not, it’s still a serious risk to have kids with anyone too closely related, but level ramifications seem really harsh, especially thinking of situations like adoption where someone could end up there accidentally. And to your point, it isn’t the only way to end up with that kind of risk profile.
Good thing that it’s possible for a couple to take a test that gives a good measure of their degree of consanguinity.
This is a particular risk not only in countries with first-cousin marriage, but in those with small founder populations. For example, Iceland, where the government provides this measure to any couple who asks, so that they can make an informed decision about the risk before reproducing.
And ethno-nationalists can choke on this fact: the best strategy to reduce the risk of genetic defects is out-marriage. The less closely genetically similar two partners are, the lower the odds of autosomal recessive disorders afflicting their offspring. So I did the rational thing, and married someone whose ancestors came from a different part of the world than mine.
We are talking of a huge difference between risks to a child by parents over 30 compared to a clear 15% risk with cousins having children. The actual risks are higher where there are recent (parent and grandparents) who were also more closely related.
It’s not a clear 15% risk. The actual risk to an individual child is in the 4-5% range, compared to 2.55% for the population as a whole.
Isn’t that likely compounded if children of first cousins end up reproducing with children from first cousins, and so on? As a one-off, those figures might be the case, but could well increase if the practice is endemic.