Steve,
Interesting post!
Prof Hoekstra is quite right. The human race -- particularly the Western
branch so far -- is steadily acquiring deleterious gene variations. Medical
interventions of all sorts -- including IVF procedures, extreme premature
births, caesarean births -- are the obvious ones and all have already been
scientifically implicated to a greater or lesser extent in bringing
individuals into existence who would not have survived in former times.
IVF procedures randomizes the selection of eggs and sperm which, otherwise,
would have been naturally deselected. Eggs which are not quite perfectly
developed and sperm with too slow tails tend to be used more often than
would have been the case with natural fertilization. Extreme premature
births of babies tends to save foetuses with faulty gene variations and
which otherwise would have been naturally aborted at a late stage. (Most
foetuses are naturally aborted at a very early stage, even though the
mothers are unaware of this.) Caesarean births are increasing the
proportion of future mothers with too thin hips caused by sub-optimal genes
so that, if this continues into the very long term future, all births would
have to done by Caesarean methods.
Much more serious than the above is the effect of the increasing
equalization of family size between all classes of a population. In a state
of nature, the fitter genomes of mothers and fathers tend to produce a
larger number of offspring than less fit parents. This is indeed the very
basis of evolution. The less fit, particularly those with seriously harmful
genes, become crowded out.
So far, we have no need to worry too much, according to geneticists who
have written about this matter -- such as Prof Hoekstra hmself. The human
genome, as in all species, already contains a large number of harmful
genetic variations. These occur naturally as mutations occur --
particularly at the stage when eggs and sperm are being manufactured in
their respective germlines, when chromosomes are being split and exchanging
genes in complex ways. Some 200 dominant deleterious genes have already
been identified and, further, it is estimated that anything between 1,000
and 3,000 sub-optimal recessive variations exist.
Usually, dominant harmful genes are extinguished fairly quickly because
they reveal physical or mental handicaps visibly, and females don't tend to
choose potential fathers with these obvious faults. Recessive variations
are, if anything, more serious because they can be carried for generations
without revealing themselves. They only come to the fore when a mother and
a father both have the same recessive and have children in which the
variation is fully operational.
Thus, harmful recessive variations are extinguished in the overall human
genome much less frequently than harmful dominants. Nevertheless they do
disappear in due course. Meanwhile new ones are constantly arriving by
natural genetic accidents -- mutations. So a state of balance occurs in a
large population between harmful recessive genes which are being naturally
acquired and those which are being extinguished.
The point is: Are mankind's present artificial medical procedures adding to
the total stock of harmful genes faster than they are being extinguished by
means of natural selection or by sexual choice of partners by the females.
The answer must be yes. However, so far, considering the very large number
of naturally occurring harmfuls, the modern causes are still only marginal.
In short, the more that geneticists can discover about harmful genes and be
able to identify them, the more that the present dysgenic effects can
become neutralized by DNA sequencing in potential mothers and fathers who
may then decide that it would be better to choose another partner in order
to avoid unhealthy or handicapped children. We will then be practising
eugenics in a positive way just bas we are already practising eugenics --
albeit unwittingly by most people -- in a negative way.
Keith
At 19:08 04/03/2010 -0500, you wrote:
http://world-nuts.blogspot.com/2010/03/genetic-inferiority-threatens-mankind.html
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Keith Hudson, Saltford, England
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