A recent University of North Carolina at Chapel Hill study
coordinated by Dr. David H. Overstreet, associate professor of
psychiatry at the UNC-CH School of Medicine and a member of Skipper
Bowles Center for Alcohol Studies showed "a strong correlation
between men's preference for sweet tastes and whether their twin
brothers liked sweets too." (It also suggested a correlation between
alcoholism and a preference for sweets.) Preliminary results of the
continuing research, that included 19 pairs of twins, were presented
Nov. 6, 2000 at a Society for Neuroscience meeting in New Orleans.
(See news article at: http://www.eurekalert.org/releases/unc-tss110300.html)

Meanwhile the BBC is reporting that an American team headed by
Professor Robert Plomin may have already zeroed in on the few genes
responsible for IQ variation in a Tuesday, 8 August, 2000 article
entitled "Genius of Genes". "The researchers, working for the US
National Institutes of Health, analysed the DNA of 200 of the
brightest kids in America and compared them with the genetic material
from ordinary children." Although what the genes do isn't known the
BBC article theorizes that the genes may turn out to "help make nerve
cells."

Now for some thorough speculation, on my part, before it's too late
to embarrass myself:

That first study reminds me of a stray fact I stumbled over many
years ago in a popular work on Psychology by the somewhat
controversial Dr. Hans Eysenck, which might be of relevance to the
second. If I remember correctly the story he told there, during the
Second World War, everyone entering the U.S. Army was given an IQ
test. Someone who knew statistics and didn't want to end up at the
front busied himself for years hand-calculating correlations between
all the variables in the induction data, looking in particular for
relationships to IQ scores, just to keep themselves busy with
clerical work and well away from the firefights. Eysenck dismissed
out of hand the rather startling result - the highest correlation
found was a very strong .63 between an inducted soldier's number of
fillings and IQ! And this from a truly huge sample.

Somehow, Eysenck was utterly unimpressed, concluding that this only
proved how worthless empirical investigations could be in the wrong
hands. Not a very scientific attitude to my mind, then or now. But
here's some speculation that might make sense of that remarkably
statistically significant result, obtained from millions: just maybe
what's most clearly inheritable about intelligence, and responsible
for most of the present variation - is how much of a gas-guzzler the
brain is tuned to be. After all, the brain uses up about 20% of the
glucose/energy of the body as a whole, I believe - a very substantial
amount that is disproportional to its weight. In more traditional
circumstances when food shortages were predictable hurdles to
survival, having a brain with better glucose mileage which just
sipped glucose might have an obvious evolutionary advantage. Of
course, such energy efficiency is not of great practical use anymore
in first world nations, at least, nor has this been the case for
generations. It seems reasonable to me to suppose that the more you
burn, the more you'll yearn - the more likely you'll be seeking out
readily available energy in carbohydrates, including sugars like
sucrose that are responsible for cavities. Just to fill this out a
little, sucrose is especially attractive to the mutans bacteria
responsible for cavities, and sucrose releases it's energy very
quickly compared to, say, fructose (fruit sugar). Also, cavities are
most closely correlated with the frequency of sugar intake
(particularly sucrose), not simply quantity. To cite anecdotal
evidence: at Sandia Labs the carbohydrate consumption per capita by
researchers is said to be extremely high, leaning towards frequent
snacks such as pop and chocolate bars that are loaded with sucrose.
The high-powered brains there, at least, would seem to be gas-
guzzlers.

Against this, it could be argued that those who have high IQs are
therefore given jobs that demand more thinking, and who then turn
into heavy fuel-burners, in which case no simple genetic difference
could be expected to be directly responsible for the variation in IQ
between humans. But what of manual labor? Does mental activity
require more frequent or more available energy sources than muscular
effort - and therefore lead to more cavities? Possibly there's a
difference, not so much in the quantity of energy and fuel required
for heavy thinking, as the kind and frequency. Maybe Stevedores ate
quantities of more complex carbohydrates, less frequently.

Of course there are other explanations. Maybe wealth correlated
highly with being able to purchase both books and dental services
back in 1940, etc. And whether alcohol fits into any of this I'm
wouldn't care to guess. Certainly it's an energy source, and burned
preferentially (thus letting other substances concentrate in the
blood.) But whether it would be sought out for its value as an energy
source is another question entirely. If this is so for at least some
of the population, I suppose it's not impossible that alcoholism
could turn out to be a side-effect of recent evolutionary trends
toward greater neural energy use and linked energy-seeking behavior.
It's hoping for a lot to seek out explanations that simple, even as
partial explanations, but it might be worth mentioning as an
hypothesis.

I also wouldn't care to speculate whether, if the above is tue, it
might be that significant gene-frequency change has occurred in some
populations since the introduction of Agriculture, and perhaps even
since the agricultural revolutions that accompanied the Industrial
Revolution in the nineteenth century - thus offering what might be
taken to be a relatively innocuous explanation of "IQ differences"
between populations, if there are any to be accounted for. Despite
some recent studies showing selection acting more rapidly than had
been thought, that's a very short time span, evolutionarily speaking.
I suppose it might be thought that the second-best thing to our
discovering no IQ differences between human populations would be to
discover that there are such differences, but that their cause is
trivial, and easily altered if we choose to do some quick human re-
engineering. But I'm not getting so far ahead of the field that I'm
saying this is so, or any remedies desirable.

If all this rank speculation holds, it might even be that increasing
fuel consumption is a fairly simple tweak, perhaps just one gene (or
any one of several). For future generations, this might be an easy
way to dramatically alter human beings and society as a whole in
train. I'm not suggesting that such tinkering should happen: although
as a "gas guzzler" myself, the prospect of a world teeming with
chocoholics grubbing for more sweets seems pretty normal to me - for
all that it may make Lord Winston (who recently called for critical
discussion of human re-engineering) shudder.

That's a whole lot of airy speculation to be tagged onto one article
about the genetics of sweet-craving, and a hint from a gene study
that's not finished, I know. But, if it's any defense, the astronomer
Kepler was worse still at charging well beyond the available data, to
name just one miscreant.

Also, apologies are in order as my citations could obviously use some
plumping up here - if you know relevant bibliographic details, I'll
welcome them with gratitude and some shame.

PS. - It's been a long time since I read Eysenck - if it turns out
that the .63 correlation was an inverse one, just shoot me.

PPS. - In "A Neural Basis for General Intelligence." Dr. John Duncan
of the Cognition and Brain Science Unit of the Medical Research
Council in Cambridge, England and his colleagues recently reported
research in Science showing the dramatic importance for IQ-test
problem-solving of the lateral prefrontal cortex, a small part of the
brain. I take this to be independent of my speculations, without
implications either way for the sort of hypothesis I've put forward
here.

Russell Johnston