Sexual balance
From your review of his book The Dangerous Passion
(11 March, p 53),
it appears that David Buss expresses the opinion that men are more promiscuous
than women.
I’ve read this opinion before, but not from a man of science. Men cannot have
sex with women more often than women have sex with men. It is physically
impossible.
The idea that men are more promiscuous than women should be seen for what it
is, a misconception based on fantasy and not a valid scientific fact.
Evolution's fuel
Your article speculates on the role of “junk” DNA
(1 April, p 38). My
experience with self-evolving computer programs is that they evolve much more
quickly and successfully if they have plenty of “junk” instructions to help them
mutate. Conversely, structures in which every component is critical typically
collapse when something changes randomly.
If this applies equally in biology, one would expect to find the
fastest-evolving creatures to be those with the highest percentage of junk DNA.
Since human beings have evolved quicker (or further, anyway) than any other
living entity, it is not surprising to find we score 97 per cent on the junk
index.
It would be fascinating to see how coelacanths and other “living
fossils”鈥攚hich have failed to evolve鈥攔ate in comparison.
Chewing on antlers
Adrian Barnett, in his article on Irish elk
(25 March, p 36), expresses
uncertainty as to the function of antlers. Surely, as in the case of modern red
deer, they were reservoirs of minerals which were gnawed by the hinds at the
time when their calf fetuses were growing rapidly.
The antlers must go somewhere after being shed. On my farm in Scotland I have
seen not only hinds but also cattle and sheep gnawing at shed antlers, the soil
being very deficient in calcium. Were it not for this, the place would be metres
deep in antlers.
Thin and holy
The theory that semi-starved humans live longer
(25 March, p 21) has been
tested and falsified. For thousands of years, religious ascetics have done
exactly this, and few lived beyond the normal human lifespan.
The evidence is particularly convincing since the details of their lives were
closely documented by people hungry for miracles. Cure blindness and raise the
dead, certainly. But live to 150? No way.
The best recipe is to cut out smoking and combine regular exercise with a
sensible diet and low stress. You should make it into your eighties.
Magical light
It seems that material with negative permeability and permittivity is not
merely exotic but magical.
The illustration in your news item
(25 March, p 5) shows light entering it
being bent backwards, but leaving it without deflection. Even more remarkable,
light entering the normal glass block beside
it is also deflected on entering the glass but not on
leaving it.
Flying an idea
We have been most interested in your items on the Russian “ekranoplan” and
the Japanese trains that operate on the same principle (
25 March, p 14; and
11 March, p 11).
We have been working on a further development of this idea for
some time.
Briefly, we believe that, by extending the “wings” and adding further motive
power, such a device could be persuaded to leave the ground altogether. This
would enable it to move directly through the atmosphere to its destination,
where it could alight on a suitably prepared area where its passengers could
embark and disembark.
We propose to call this an “air-o-plane”, or possibly “aer-o-plane”, and if
all goes well we shall have a prototype ready for testing by about 2003.
Sonorous athletes
I was intrigued to read about the robotic composer (RoBoser) that makes music
in response to sensors in the audience
(25 March, p 9).
The potential for such a system at sporting events seems huge. One can
imagine a lively, upbeat piece of music associated with arms in the air and flag
waving, contrasted with a solemn dirge when flags and heads drop.
Taking this idea one step further, why not incorporate sensors into
individual athletes in Sydney this September? The music composed by RoBoser
for a pole-vault or gymnastic event could be amazing.
After the deluge
“It is frighteningly clear” that Fred Pearce has not understood the extreme
nature of the recent southern African floods
(25 March, p 16).
It has not just been a wet year down here, with 75 per cent more rain than
normal. Years with 75 per cent more (or less) runoff than average are the norm
in our highly variable rivers. What was abnormal was to have twice the average
annual flow going down the Limpopo (to quote one example) in just eight days.
Even in our terms, this is an extreme event.
It was the exceptional rainfall that resulted in the unprecedented floods.
The volumes involved would have filled all the dams in the river basin concerned
five times over even if they had been completely empty to start, with minimal
effects on flooding.
Dams built to store water to keep farmers going during inevitable dry periods
will damp down “normal” flood flows even if they are full, as any first-year
hydrology student will confirm. But to suggest that they could somehow be
managed to mitigate floods of the severity of those recently experienced is,
politely put, misleading.
We hope that an independent UNESCO-led review of the flood events will be
carried out at the request of Mozambique’s government. What we believe this will
show is that the flooding was an extreme event, that no actions to manage dams
or catchment land use would have had much impact, and that the appropriate
response is to strengthen existing monitoring and early warning systems, to
control settlement on the flood plains (so called for good reason) and promote
activities to limit human and economic casualties.
We also hope for guidance on the likelihood that global climate change will
mean this kind of extreme event becomes more common in the future.
Letter
Pearce’s assertion about the Concepci贸n dam, namely that “floods in
Tegucigalpa . . . were seriously exacerbated when engineers made an emergency
release of water from the Concepci贸n dam” can easily be refuted by the
fact that this dam has only an ungated crest spillway and a small outlet at the
bottom for drinking water. It is therefore impossible to create an artificial
flood. The “wall of water” that the survivors describe having seen was actually
caused by a rock slide into the Rio Grande upstream of the city.
Secondly, the benefit of the El Caj贸n multipurpose arch dam in
Honduras during Hurricane Mitch is not mentioned. Upstream of this dam, which is
226 metres high, damage was substantial, the worst
event being a major landslide above the town of La Libertad which caused
considerable loss of life.
The owner of El Caj贸n dam estimates that the incoming flood to the
reservoir was 9800 cubic metres per second鈥攍ikely to happen only once
every 500 years鈥攁nd 70 per cent of the probable maximum flood. The
reservoir level prior to the passing of the hurricane was 13 metres below full
supply level. Within 70 hours this level had risen by 16 metres, and some 1500
million cubic metres of floodwater had been retained.
As a result of this flood control, the maximum discharge experienced
downstream of the dam was only 1200 cubic metres per second. The presence of the
El Caj贸n dam, and its appropriate operation, thus considerably reduced
downstream flood levels.
Baby blues
Your correspondent Norman Sheppard asserts that it is useful for depressed
mothers to withdraw from society so that they can better nurture their infant
(1 April, p 53) .
In fact, the greatest and most damaging withdrawal that they make is from the
child. There is extensive research evidence showing this and a substantial body
of research demonstrating that the potential damage to children’s development is
great.
Postnatal depression is a serious, immensely disabling and life-threatening
condition that can ruin the lives of mothers and their families. And the idea
that male doctors are imposing treatment on uncomplaining women because they
perceive illness where none exists is naive, simplistic and not borne out by the
facts.