What is so fascinating (and politically important) about the future avoidance of genetically handicapped children is whether tests will become widely available or whether their costs structure will develop so that they will be taken up preferentially by social elites.
Will the tests be cheap enough so that they will be available to all prospective parents in a country’s population, or will they accrete a cost-grading structure so that they will only be fully affordable by an elite sub-population? Will protective practices develop?
In some advanced countries such elites are already discernible as having substantially better health and intelligence already. And, because their young people tend to meet preferentially with other similar young people at their elite schools, universities and places of work, they tend to marry among themselves and thus take their particular qualities into the next generation, tending to remain a distinct sub=population.
It’s impossible to know what will happen. So far. well over 4,000 genetic diseases have already been identified. Each of us has about 23,000 genes in doubles, one of which derives from the mother and the other from the father. In each case, one of the doubles could exist as a harmful variation caused by a mutation. In these cases, the disease exists in a weak form (recessive genes)and doesn’t have any outward effect — its bearer is called a ‘carrier’ only.
If, however, any of these single mutations meet up again after partnership and marriage, a further fertilization could result could be matched pair of mutations causing a handicapped child, ranging from someone with a permanent but trivial defect to a much more serious disease which may need lifetime care or brings about premature death.
Thus there could easily be 23,000 genetic diseases that already exist all over the world but are only fully visible when a child is born to unsuspecting parents — unless detected beforehand. There could, in fact, be many more than 23,000 genetic diseases because genes are so long and complex that many genes carry more than one mutation. Some of these could be greatly deleterious if matched up later during fertilization.
Some single-carrier recessive diseases such as cystic fibrosis are surprisingly common in some parts of Europe and thus sufficiently serious to be screened away regularly already during, say, IVF treatment, in order to to avoid children with the full-blown double-gene version who are destined to die before adulthood.
But with a possible 23,000 genetic diseases in existence — or even more — then the potential programme for extinguishing all possibilities is immense. Furthermore, with increasing inter-marriage between differeent ethnic groups in modern times then all genetic diseases that aris in different parts of the world tend to become more widely dispersed — in a non-expressed single carrier state — and remain longer in the population before being extinguished naturally, which used to happen when we lived in smaller non-travelling hunter-gatherer groups for thousands of years. Also, besides the natural extinction of genetic disease ass they arose in children most, if not all hunter-gatherer groups would cull handicapped children at birth — if not instinctively then very close — because such groups couldn’t afford to carry permanent dependents.
It’s a huge programme for mankind and will undoubtedly continue for many centuries, perhaps millennia. But now that the first and most respected genetic testing firm, 23andMe, can now test for a small number of genetic diseases and has now been given the go-ahead by the US Food and Drugs Administration then we can be sure that the race is now on between all intelligent couples who hope to have children.