A story about a most unusual medical condition in an isolated village in the Dominican Republic fascinated me this morning. This condition probably doesn’t exist anywhere else in the world yet the genetic cause of it is of far wider relevance. It involves in-breeding. There are, in fact, hundreds of other cases of in-breeding all over the world in isolated villages — or even in strict religious groups living within a dense society all around them (such as the Amish in America) — giving rise to conditions that vary from handicaps that are relatively trivial to those of the most debilitating nature and those sudden deaths of young children which are so poignant.
The one I’m reading about concerns a village where dome of the children who are born girls become boys at puberty. They are not actually girls but boys who look like girls because they don’t have the usual penis and testicles. In their mother’s womb, they missed out on the natural injection of a specific form of testosterone into their gonads which occurs in the early weeks.
Because they look identical to girls when born they are given girls’ names — though, interestingly, some of them don’t think like girls, behave like tomboys and are exhilarated when they discover that they are becoming boys later. At puberty, when every boy receives another surge of testosterone — this time a more powerful one — these ‘girls’ also get a charge and quite quickly develop the appropriate male apparatus and can become normal male adults
The cause of this condition is a double charge of a particular recessive mutation derived from parents who each had a single copy. Such parents don’t always produce children with a double mutation. On average, only one in four children will be affected. Two in four of their children will only have one copy each and they’ll have no physiological consequence. And one in four of their children on average will have no copies of the mutation at all. Although in this particular village, only 1 in 90 children are these ‘delayed-boys’, working backwards mathematically suggests that approximately 1 in 19 of all the adults in that village, whether males or females, have a single copy.
This mutation incidence of 1 in 19 is too high to be comfortable and, when it is common in a wider region than individual villages it is, in fact, rather similar to the rate of recessive mutations which cause some well-known serious genetic diseases. For example the incidence of single mutation copies of cystic fibrosis in certain regions of the southern Mediterranean countries is about 1 in 19 adults also.
However, in more modern times as young women are able to travel further before they choose their partner — perhaps in a distant university — the risks of children with cystic fibrosis decreases in those Mediterranean countries. But the total risk, though much more diffuse, remains. The incidence of single-copy cystic fibrosis occurs in only one in several hundred individuals in northern Europe.
Eggs that are fertilized externally with a male sperm in an IVF clinic are tested for cystic fibrosis and up to 100 other genetic diseases, before the mutation-free eggs (1 in 4 of them) are re-inserted in their mothers’ wombs. These are only a few of the 4,000 genetic diseases that are caused by the matching of single copies of mutations.
However, several research teams are now developing methods of detecting double-copies of genetic diseases of a foetus from mothers’ urine very early in pregnancy when abortion can be easy and safe. They’re not available yet but soon will be for one or two conditions and, in due course, will be able to detect increasing numbers in the list of 4,000. But this would be an expensive and very long term programme before serious ‘genetic cleansing’ on a wide scale could ever be achieved.
In fact, it would never be perfectly achieved because, as it happens, every time a sperm fertilizes an egg, mutational mishaps occur and a small proportion of them turn out to be responsible for genetic diseases at some point in the future. Because of this, the whole human population is gradually accumulating recessive mutations and this is why at least 4,000 genetic diseases are identified already. In due course, as is already happening with some genetic diseases such as cystic fibrosis, the risk of any child being born with a genetic disease is gradually rising, albeit very slowly for now.
For the almost complete elimination of genetic diseases working one by one down the known list, it would require a highly systematic programme over a period of many centuries, perhaps millennia. Governmental structures are relatively ephemeral. Such a programme is therefore unlikely ever to be achieved except by a much faster process of voluntary choice within self-conscious populations or classes. The research projects bringing about tests for early identification will be expensive. In other words this will become a personal service available on a cost basis in the same way that normal consumer goods and services already are. The possibility of a Huxleyian “Brave New World” is already strongly apparent or at least social bifurcation.