Displacement activity
You report recent findings that suggest that the coronal ridge on the human penis acts as a “semen displacement device” (9 August, p 16). While its efficacy in doing so is interesting, there are a few questions regarding the utility of this function. First, there is the as yet unexplained female emission of semen about 20 minutes after intercourse, which is generally responsible for removing a significant proportion of what semen is still within the vagina. Also, the vagina is an acidic environment, and most sperm there die within about 45 minutes. Sperm can certainly live for several days within the body 鈥� but only after they have passed through the cervix. I would like to point out that once sperm has passed through the cervix all the coronal ridge scraping in the world isn’t going to help.
So in order for this to have been a significantly useful function of the corona, women would have had to have multiple lovers within 45 minutes of each other, and potentially within 20 minutes. While I have known one or two women in my lifetime where this might have been the case, they are certainly in a small minority.
Seminal work
Ken Smith worries that vasectomy may expose him to carcinogens in undischarged semen (Letters, 9 August, p 28). What is more worrying is what happens to these possible carcinogens from men who have not been vasectomised. Do the antidepressant effects of your partner’s semen (29 June 2002, p 5) outweigh the suspected cancer risk from semen? Women should be told!
鈥� Douglas Fox says no studies have been done on this risk. But the reason that retention of seminal fluid may be harmful to the prostate is that it exposes the gland to carcinogens for extended periods of time. Semen probably does not stay in women long enough for this to be a problem.
For the record
鈥� Thomas Malthus published An Essay on the Principle of Population in 1798, not in the 19th century (2 August, p 3).
鈥� Our article “Behind the mask” gave Sudhir Agrawal the title of chief executive of the biotech firm Hybridon (19 July, p 32), when in fact he is president and chief scientific officer of the company.
Running on empty
Although running vehicles and aircraft on oil-derived liquids may have a limited future, there are many alternatives to heavy oil and oil shale that involve using fossil fuels as intermediate steps to a hydrogen economy (2 August, p 4). The technology for converting gas to liquid fuel is improving constantly and most of the major oil companies now have such plants. Here in Australia most taxis and many cars run on gas, and most modern petrol engines can be easily and relatively cheaply converted.
So the probability of suddenly finding nothing at the pump to put in your car is very low for at least the next generation, and maybe two. You may pay more for it 鈥� but the enormous global differences in price at the pump suggest that there is lots of room for price adjustment in the rich economies. Just compare the US price of 40 莽 per litre with the British equivalent of $1.30. Whether or not there is the political will is a different question, of course. Developing countries may have to look at political solutions such as state oil companies to keep prices down and ensure that their resources are fully utilised for the benefit of their populations rather than the benefit of the multinationals’ shareholders.
Letter
There are huge resources of frozen crystalline methane hydrates located at mid-oceanic ridges and under the frozen Arctic ocean. Research scientists in the US navy recently estimated that frozen methane resources represent at least twice the known global fossil fuel resources. Until we see the arrival of the much-vaunted hydrogen economy, this exotic resource may represent a clean and (relatively) environmentally friendly alternative.
Creative spark
Reading Igor Aleksander’s article I was struck once again by the fact that the driving idea behind the attempts to create a conscious machine is that the machine must be able to respond creatively to as many situations as possible (19 July, p 40).
But surely what characterises human consciousness is the initiation of ideas. This creativity drove early humans not merely to improve their hunting methods and tools, but to paint on cave walls, make decorative objects to wear, and probably to make music and dance. Humans are constantly impelled by desires, imaginings and fantasies, way beyond a mere response to needs as they arise, or mere interaction with the environment.
In Isaac Asimov’s classic I, Robot, the ultimate robot became humanised when it set out to do things it had not been programmed for, and conceived of things not yet thought of. This seems to me to be just as feasible in the foreseeable future as intergalactic travel.
Calculating risk
It should come as no surprise to anyone that a little sunlight is good for you (9 August, p 30). The evolutionary evidence is that skins became paler as humans migrated north from Africa, probably to better utilise the available sunlight.
The increased incidence of skin cancer is more likely related to our modern propensity to lie in the sun for hours to generate the sort of tan our ancestors would normally achieve over years of casual exposure, rather than two weeks on the beach. Also our skin is subject to a far wider range of potential carcinogens than previously thought.
So if cosmetics, environmental pollution and diet can all be implicated in the increased incidence of skin cancer, attributing it all to sunlight exposure is probably inaccurate in any case. Western culture now has such a “no risk” mentality that we have become conditioned to thinking in absolutes: alcohol is “bad”, cholesterol is “bad” and sunlight is also “bad”. It will do us no harm to become accustomed to relative risk as a way of managing conflicting health advice.
Coherent waves
I was disappointed to find several technical inaccuracies in Celeste Biever’s article “Go with the flow” (2 August, p 38). The article mentions that Branly’s radio wave detector, more commonly known as Branly’s coherer, was replaced with more sensitive wire aerials. While wire aerials would have improved the signal strength, the coherer was still required to detect and rectify the radio waves.
The real reason engineers replaced the coherer was because it had to be mechanically tapped between each signal burst, which was very inconvenient. Its replacement was the well-known cat’s whisker and crystal, which required no mechanical intervention. The whisker was a short length of springy wire which was gently touched to a piece of lead sulphide. This whisker-and-crystal combination was used in the microwave detectors in most second world war radars, and a similar arrangement was used in the early transistors.
Another criticism is the use of the terms “solder” and “soldering” in the article. In industry, soldering has a precise meaning and refers to the process where two components are joined together by a mixture of molten tin and lead. It is quite nonsensical to extrapolate this process to cornflakes, and it is surely misleading to talk of an electrical current binding toget her such a non-conducting material. If the current is carried by water vapour, as one researcher suggests, what happens in dry atmospheres?
My own theory is that much of the observed phenomena can be explained by grains in silos and boxes picking up electrostatic charges which then discharge against the sides of the container.
Letter
Meacher states that people want to know whether GM food is “inherently completely safe”. If absolute assurance about safety were really the overriding concern about GM food, would the public not demand evidence that other food on the market is also inherently completely safe? Far from assurances on this subject, the public is constantly bombarded with information to the contrary. Yet where is the consumer demand for trials to prove the safety of non-GM food? Which pressure group demands the introduction of health warning labels for fast and highly processed food, or anything that contains significant amounts of sugar, salt and saturated fats?
People are quite willing to take risks when it suits them. If eating habits are not sufficient proof of that then just look at smoking, alcohol and other drug use.
Letter
Given your editorial in January asking for all sides in the GM debate to be clear on their motives, I am astonished by the article by Meacher.
Readers should not be fooled by his comments: now relieved of his ministerial responsibilities, Meacher is speaking on behalf of an alliance of environmental groups actively campaigning against GM crops. This campaign, with its emotive political rhetoric, poses a severe threat to a rational science-based evaluation of GM crops in the UK.
Despite the fact that GM, unlike any other agricultural technology introduced in the last century, has been regulated on safety and environmental grounds since its inception, there are continuing demands for an absolute proof of safety that is not applied to any other group of consumer products.
If you care about an open, evidence-based evaluation of any science or technology, watch what happens as the GM decision-making process unfolds in the autumn. If the decision runs against free commercialisation of GM crops then watch out: it could be your science next on the block.
Target the vector
West Nile virus is obviously a dangerous and difficult problem facing the people of Mexico and South America. I found it mildly bemusing that the main control measure cited was vaccination for the “beasts of burden” (26 July, p 12). Even if there existed a vaccine for animals other than horses (and there doesn’t, as your article stated), it seems a hopeless measure. It would be exceedingly expensive and animals would need booster shots after six months anyway.
A more effective approach would be to control the vector population 鈥� the mosquitoes. This has been done extensively in the past to help control parasite-borne diseases like malaria. In Thailand, there was a very successful programme of stocking bodies of fresh water with varieties of native fish that prey on mosquito larvae.
Similar biocontrol measures targeted at the vector have utilised a range of carnivorous aquatic insects, each endemic to the area being treated. These carnivorous insect larvae are among the hardiest of aquatic organisms, and like mosquito larvae can survive in even the poorest conditions. Another simple and cheap measure is to eliminate standing bodies of water.
GM safety myth
Sorry, Mr Meacher, but no one will ever prove that genetically modified food is “inherently completely safe”, however much the public craves that knowledge (2 August, p 21).
As pharmacologists know well, it is impossible to prove that a new drug is completely safe 鈥� all you can do is administer it to a large number of humans, then stand back and wait for something nasty to happen. The nastier and more common the adverse effect, the sooner it is recognised. When malformed babies were born to mothers taking thalidomide, it was recognised very quickly. However, if the nasty event is rare and sporadic, it may take a long time to spot. The antibiotic chloramphenicol was widely prescribed for years before doctors realised that one patient in 40,000 died of aplastic anaemia following treatment.
Exactly the same holds true for GM food. A huge clinical trial is already in progress: we in the US consume GM food daily, while a control group, the population of Europe, does not. As far as I know, some billions of person-years of GM food consumption have not yet been associated with any statistically significant changes in our relative rates of morbidity or mortality, though statisticians on both sides of the Atlantic are probably watching closely.