"Gordon Brown and his wife Sarah have been hit by a fresh challenge after
it was discovered that their baby son has cystic fibrosis." The Times, (30
November 2006)
It is sad to learn of the condition of the latest son of the Chancellor of
the Exchequer and his wife. It is a genetic disease and the faulty gene is
carried recessively by 1 in 25 of us, so the odds (25 x 25) against the
gene becoming dominant in any child are not excessively high. It affects
about 7,500 babies in the country and is the most common inherited disease.
The life expectancy of affected individuals is no more than 31 years, even
with modern therapeutic techniques.
In the not too distant future it is highly likely that intending parents
will avoid such genetic mishaps by DNA testing. This is now increasingly
carried out with persons with a family tree which makes them more than
usually prone to carrying Huntingdon's or Tay Sach's and several other
serious diseases. In addition, in vitro fertilization and pre-implantation
examination is being carried out on an increasingly large scale.
Thus, as far as negative screening procedures are concerned, we are already
deeply into genetic engineering. No matter how many spanners are attempted
to be thrown into the works by religious objectors or ethics committees
(often the former in disguise) and government legislation, DNA screening
will be increasingly demanded by intending parents. Indeed, it will not be
all that long before any intelligent pair of young people will want to be
screened for deleterious genes long before their relationship goes too far.
That is, for particularly deleterious genes, such as those above. However,
all of us carry something between 1,000 and 3,000 defective genes and it is
increasingly going to be a matter of careful judgement as to where to draw
the line in the case of particular couples. This is because our genes do
not have individual additive effects that can be unambiguously identified.
Some "bad" genes are also associated with other "good" genes and the net
effect is slightly beneficial. A check-list of what is desirable and what
is not desirable in every case simply cannot be drawn up, nor ever will be.
It is now being realised that genes act in groups and also in strict
cascade sequences in early development in the womb. In the case of a great
many of what may be identified as bad genes, screening them out will only
result in the early death of the foetus.
The only deleterious genes that can be successfully screened out will be
those that have arisen comparatively recently in human populations -- say,
in the last few decades or centuries -- which are are not yet deeply
incorporated into genetic cascades. It will be comparatively easy to
identify these -- and indeed, freshly mutating ones. As for the remainder,
these will have to be left to the normal course of evolution, the
individuals concerned either dying before puberty or whose conditions are
severe enough for them not to be attractive enough to another sexual partner.
But besides newly mutating deleterious genes, some genes with positive
selection effects are constantly arising -- that is, in individuals who are
more sexually attractive either because (in the case of males) they are
more economically competent than other males or because (in the case of
females) they are more physically attractive. As it is females who do most
of the deciding about marriage and parenthood, and as economical survival
is becoming increasingly complex, then mutations to brain genes will be
more heavily selected than those responsible for enhanced physical features.
Since about 40,000 years ago there have been two major mutational changes
to brain genes and these have been working their way through the total
world population by the most usual method of being intuitively selected by
females. But, from recent genetic evidence, it is known that hundreds of
mutational changes are constantly occurring and while the vast majority of
these will be minor ones there could be some which result in major
improvements of brain function and better economic prospects for the
individual. Once these new skills are perceived, and the particular
mutations identified, then we can be certain that sperm containing these
will be preferentially chosen by IVF mothers or by girls who ask to see the
DNA print-outs of possible marriage partners.
Will this then be natural selection or genetic engineering?
Keith Hudson
Keith Hudson, Bath, England, <www.evolutionary-economics.org>
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