At 00:57 07/11/2010 -0700, Pete Vincent wrote (in a pleasant non-aggressive
way):
On Sun, 7 Nov 2010, Keith Hudson wrote:
Wherever intensive manual agriculture was practised around the world,
> the nutritionally poor diet (carbohydrate-rich, protein-poor) resulted in
> short and underweight individuals compared with man in Neolithic times.
This
> was due to epigenetic effects on the normal developmental genes in the
> embryo. When diets began to improve during industrial times -- from
about 200
> years ago in Europe -- epigenetic control began relaxing in stages and,
> within about five or six generations, the size and weight of babies
improved
> each generation -- and, of course, in the adult. In the UK, for example,
> upper middle-class individuals had recovered full Neolithic size and
weight
> about three generations ago while most of the population are only just
about
> reaching it now. (Americans got there sooner. Even as late as the 1940s
when
> American soldiers were arriving in England preparatory to the invasion of
> Germany-occupied Europe, it was noticed that on average they were several
> inches taller and many pounds heavier than English soldiers.) The full
> recovery of normal weight and size appears to take about five or six
> generations of a nutritionally adequate diet -- each new generation
stepping
> upwards, as it were, (roughly a gain of about a quarter-pound in birth
weight
> each successive generation). The same effect is now occurring in parts of
> Asia because they are now weaning themselves away from an almost
exclusively
> rice/millet/wheat diet. The Japanese are still about two generations away
> from full epigenetic recovery while other Asians such as the Vietnamese or
> the Chinese are still distinctly small and are still several
generations away
> from full Neolithic stature. (The Dalits of India are still probably a
couple
> of centuries away from full stature -- if indeed, they ever receive an
> adequate diet.)
>
I'm afraid this doesn't quite work. I believe the real reason for north
americans being larger is the large amount of dairy they consume, but
I'm not sure.
Yes, this must be significant. This is probably one of the main reasons why
the American soldiers who came to England in the 1940s were so much taller
and heavier than the English soldiers. But there was meat also. (I remember
that in the '50s [the UK still being on war-time food rationing] when my
[apparent] girlfriend took me to a party at an American airbase in
Yorkshire, I could hardly believe the buffet food that was laid out there
-- particularly all the different sorts of meats. [It turned out that my
girlfriend really fancied an American officer -- I never saw her again
after the party! Gosh, she was lovely! Her name was Marion. I'll never
forget her.] )
At any rate, the problem with your thesis
It's not my thesis. It's just that I try to keep up-to-date with genetics.
The fact of epigenesis, particularly as it affects body size (but much else
besides), is now becoming well-established in biology. (It's only really
been adequately demonstrated since the Human Genome Project in 2003, so
there are still some old-diehards around.) We have about 20,000 genes and
epigenetic control over them produces at least 100,000 two- or three-gene
coalitions which affect our physiology and behaviour. Their subtleties and
predispositions will probably take many decades to identify -- if at all to
identify fully because new epigenetic settings can take place at any time.
is that both
europeans and asians arriving in north america, who adopt the north
american diet, have children who grow to the north american norm, in
the first generation;
I would be deeply interested in any evidence that supports your statement.
If a typically small-sized Asian couple arrive in America their children
will still be small, no matter how adequate their diet. If they have a son,
however, then his epigenetic settings will adjust slightly in the years
before puberty [in the pre-sperm DNA machinery in his testes] and, even if
he marries an underweight Asian girl, he will have children who will, on
average, be taller and heavier than his wife and parents. (Changes in
epigenetic settings only take place in boys in the years before puberty.
They don't occur in girls because they are born with all the ['finalized']
eggs they will ever use in their lifetime. On the other hand, boys only
produce [epigenetically adjusted] sperm after puberty. However, when he
becomes a parent in due course his epigenetic changes are inherited by his
girl offspring as well as boys.)
Keith
and this has been true for the last half century,
which is the period in which north america has been well stocked with
nutritious food. (I'll leave aside the subject of the rise of junk food,
and the current decline in nutritional habits.)
-Pete
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Keith Hudson, Saltford, England
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