Why Can't Elephants Jump?: And 101 Other Tantalising Science Questions - New Scientist (2010)

Chapter 2. Our bodies

Our daughter Aisling would like to know why we have evolved two bodily systems to excrete waste products. Why do we have to both poo and wee?

Maeve and Chris Tierney

Edinburgh, UK

Strictly speaking, the question is misplaced. We do not ‘excrete’ faeces because our bodies are long fleshy tubes which can be thought of as extremely elongated doughnuts. In a doughnut, one would not consider the hole to be ‘inside’ the cake. Similarly, the tube from our mouth through our gut to our anus is technically ‘outside’ the living body.

The process of ‘excretion’ is the passing of material from inside our bodies to the outside. Our kidneys excrete urine, our skin excretes sweat, our lungs excrete water and carbon dioxide, and the inside of our bowel tube excretes many things along its length to assist digestion, as well as disposing of waste products in our bile. The other excreta our bodies produce include tears, earwax, and various secretions associated with our reproductive processes. If young Aisling suffers (or is about to suffer) from spots, then these too are caused by excretions which have gone awry.

Our faeces, on the other hand, consist of undigested food and bacteria. It has never actually been inside our bodies. Apart from the bile and one or two other remnants from our exocrine glands, it cannot be regarded as excreta, despite the common use of that word to describe it.

Bryn Glover

Cracoe, North Yorkshire, UK

The types of waste we excrete have two different origins. Faeces contains the leftover, indigestible portion of the food we eat, plus bile from the liver, which gives excrement its brown colour.

Urine, on the other hand, is the result of blood filtration in the kidneys. Urine contains nitrogenous waste, primarily in the form of urea, which results from the metabolism of nucleic acids and proteins, separate from digestion. Furthermore, urine also contains water and solutes from the blood, and interstitial fluids - these are excreted to maintain water balance. Essentially, faeces are the result of a coarse, largescale process of the digestive system alone, whereas urine production occurs at a much finer scale, eliminating wastes produced by all the body’s cells.

Our two excretory systems are obvious because we have a separate opening for each: the anus and the urethra. In other organisms, the distinction between the systems isn’t as obvious. Animals such as birds, reptiles, and amphibians possess a cloaca, which serves as a common opening for both liquid and solid wastes. Insects blur the line even further: rather than having a distinct urinary system, they rely on Malpighian tubules in their digestive systems - outgrowths of the gut that perform the same filtration function as our kidneys.

Shaun Hug

La Mirada, California, US

I recently bought a spray-on deodorant. When I got it home I realised it was intended for women but, not wanting to waste money, I used it anyway. Nothing untoward happened and I received no strange looks from colleagues or friends. So what are the differences between deodorants meant for men and those that are meant for women? How might using the ‘correct’ deodorant for your sex work better than using one meant for the opposite sex, and what are the pitfalls of applying a deodorant intended for the opposite sex?

Alan Ainscroft

Leeds, West Yorkshire, UK

The primary function of all deodorants is to inhibit growth of bacteria, which feed on secretions from sweat glands. Deodorants are most often differentiated, if at all, by strength. But sex sells, so we have men’s and women’s. They have only three differences: advertising, packaging and fragrance. Remove fragrance and there are only two differences: advertising and packaging.

Formulations for both sexes contain such fragrances as flowers, herbs, spices, fruits and woods, and are judged as suitable entirely by personal and cultural taste. For example, one upscale new fragrance contains citruses, herbs, ylang-ylang, jasmine and tiare flowers, musk, tropical woods and coconut - and it’s for men. And many women buy men’s fragrances, because there is none of the social embarrassment that the reverse carries.

Toshi Knell

Nowra, New South Wales, Australia

Why do dark circles appear under your eyes when you are tired?

Tammy-Ann Sharp

New Romney, Kent, UK

The key word here is ‘tired’ - tiredness has much wider connotations than mere sleepiness.

Happy, healthy people who are merely feeling sleepy don’t usually show these dark rings beneath their eyes. Sleepy eyes are droopy and somewhat sunken in the sockets. They may also become reddened because sleepiness slows the rate of blinking, causing drier eyes and itchiness, especially if the air is dry and there is cigarette smoke about.

Sleepy people show less facial expression and tend to be poker-faced, but dark rings under the eyes are not present unless these rings were there in the first place, when sleepiness might darken them a little.

Instead, rings are often a sign of being chronically worn out, stressed and run-down - tiredness rather than sleepiness. Tired people don’t just need more sleep, but a better and more agreeable lifestyle. This is easier said than done, of course. They may even find that they have difficulty sleeping despite their tiredness, but resorting to sleeping tablets is not the answer.

As for the anatomy of these rings and whether they are due to blood pooling, skin-thinning through dehydration or something else, no one really knows.

Jim Horne

Sleep Research Centre

Loughborough University

Leicestershire, UK

Most music is written in 4/4 metre, giving four beats per bar. Why are we inclined to prefer 4/4 time? Are there circuits in our brains that tick along in patterns of four?

Michael Light

Carlisle, Western Australia

Lots of debate here about whether rhythmic choice is nature or nurture, as you’ll see below. Marching may be the origin of the 4/4 metre, but it is clearly only part of the story, for the reasons outlined in the final contribution - Ed.

I think that it’s something of an exaggeration to say that most music is in 4/4, but a great deal of it is, hence its alternative name: ‘common time’. As a music teacher, I know many students find it much harder to play in 3/4 time than in 4/4, and that they have a strong tendency to insert an extra beat in 3/4, either by lengthening the last note of each bar or by leaving a gap after it.

My own feeling, based on years of listening to students struggling rather than on any knowledge about the brain, is that we prefer 4/4 because we have two arms and two legs. March tempo comes naturally to us as an extension of the movement when we walk and swing our arms. ‘Left, right, left, right’ easily becomes ‘1, 2, 3, 4’ and any music in 4/4 can be thought of as a modified version of march tempo.

I’m convinced that if we had three legs we would find 3/4 time much easier, but that might cause other problems.

Daphne Gadd

Cambridge, UK

Popular music, be it either dance or song, does not have to be in 4/4 time. One need only look at collections of folk music to see an array of different time signatures. From the Basques to the Bulgarians you can find 5/8 and 7/16 time signatures.

In Latin America, the characteristic sesquialtera rhythm requires juxtaposition of 3/4 and 6/8 time. And let’s not start on Indian and African rhythmic complexities, which far exceed anything that can be found in the unsubtleties of western pop and rock music.

The reason 4/4 time became entrenched in popular western music during the 20th century is through the influence of jazz, which owes part of its origins to the marching bands that played at funerals for black people in the southern states of the USA. Most marches are in duple or quadruple time. Since then, the relentless and ubiquitous promotion of modern pop music has perhaps blunted many people’s appreciation of other time signatures.

Ironically, in the light of its 4/4 influence elsewhere, jazz retained its diversity with, for example, jazz waltzes. Dave Brubeck’s Take Five is in 5/4 time and many other virtuosi have used still more exotic time signatures, such as 11/8, or have even expressed two different time signatures simultaneously.

Historically, 3/4 or triple time has probably been more significant. The 19th century favoured the waltz and mazurka while in the 18th century dance music was based on minuets, which are played in triple time, and baroque orchestral overtures that began in slow quadruple time but ended in fast triple time.

The favourite dance of Charles II was in 6/4 time, Louis XIV of France loved the sarabande, Elizabeth I’s favourite dance was the galliard, all of which are - like Greensleeves - in triple time. Going back to the Middle Ages, church music was written in triple time because it was associated with the Holy Trinity.

So there is no natural predisposition for 4/4 time. It is, in fact, an illusion forced upon us by pervasive modes of contemporary western culture.

Ian Gammie

Corda Music Publications

St Albans, Hertfordshire, UK

If you were living in Vienna in the mid-19th century - the era of the Strauss waltzes - you might well have thought that most music was written in 3/4 time. Both 3/4 and 6/8 times are very common in European classical music, just as they are in classical Indian music.

All evidence suggests that these rhythms are part of cultural inheritance rather than determined by hard-wiring in the human brain. Almost all music derives ultimately from folk song and dance (much of Bach’s music is based on dance rhythms) and presumably various rhythms go in and out of fashion. Supporters of the hard-wired brain theory would need to explain the popularity of the often complex time signatures of music from all around the world.

James Hamilton-Paterson

Timelkam, Austria

My dad keeps telling me not to pick my nose and eat it. Will eating my bogeys do me any harm?

Thomas Walker

By email, no address supplied

Picking and eating are for cherries. Even if your bogeys do not affect your digestion, chewing them could affect the health of your social relationships. Try chewing gum instead.

Physiologically, eating your dried snot would not matter much. If that solid bogey that you find so toothsome had not dried out, it would have dribbled down your pharynx and been swallowed anyway, unless you intercepted it with your sleeve or handkerchief or stuck it on the underside of your chair.

For the most part, any germs it contained would be digestible or would otherwise die in your gut, but this is not always the case. Some germs do infect people via the nose, and some toxic dust particles do stick in your phlegm. It is to the benefit of your health to ensure you expel such things.

It is not for nothing that your nose hairs stop bugs and dust from landing in your lungs or gut. Blowing your nose would not stop everything, but it is better than guzzling snot.

Jon Richfield

Somerset West, South Africa

The medical literature is a delightfully rich source of information about nose picking. Firstly, nose pickers should not feel isolated or guilty about the activity. A US survey in The Journal of Clinical Psychiatry in February 1995 of 100 adults in Dane County, Wisconsin, concluded that the activity ‘is an almost universal practice in adults’. The same publication in June 2001 carried another survey, this time of adolescents in India, which found that the average frequency of pickage was four times a day.

However, too much of a good thing can prove to be a problem. Rhinotillexomania, or compulsive nose picking, can lead to epistaxis (better known as nosebleeds) or even septal perforation.

The cause of compulsive nose picking is unknown but in extreme situations may transcend habit and become a sign of a psychiatric disorder. The Wisconsin study identified one individual who spent more than 2 hours a day digitally excavating their nasal cavities.

Perhaps more worryingly, Dutch researchers reporting in the August 2006 edition of Infection Control and Hospital Epidemiology found that the frequency of nose picking correlated with the presence of nasal Staphylococcus aureus, a bacterium carried by about 25 per cent of people but which in its most horrible form can cause lurid ‘flesh-eating’ infections.

Alas I have not been able to find any studies into the effects of eating one’s bogeys, but it is almost certain that there is an Ig Nobel award set aside for anyone who is willing to tackle this important medical conundrum.

Digbeth D’Marriotti

By email, no address supplied

During long voyages in space it is possible that people will die, either from illness or because of an accident. What plans are there for disposal of the corpses?

Jessica Franklin (age 12)

London, UK

During long crewed space voyages, such as the journey to Mars that NASA was once proposing to undertake, astronauts will be exposed to numerous risks such as sustained exposure to radiation, as well as the usual health problems people face on Earth.

In light of this, it is perhaps surprising that NASA has no policy for the disposal of the dead on long missions. Interestingly, though, the US National Aeronautics and Space Act 1958 states: ‘Each crew member shall provide the Administrator with his or her preferences regarding the treatment accorded to his or her remains and the Administrator shall, to the extent possible, respect those stated preferences.’ This suggests that the possibility of death has been considered.

If an astronaut should die, there are three options for the disposal of the body: in space, burial at the destination, or to return the body to Earth.

Burying a body on another planet raises bioethical issues, particularly if there could be an impact on possible alien life. However, travelling on a spacecraft for months or years with corpses might prove uncomfortable for the rest of the crew. Nevertheless, spacecraft designed for long missions may have to include culturally appropriate disposal units or storage areas for the dead.

Alice Gorman

Flinders University

Adelaide, South Australia

As a secretary, my job involves a lot of typing. If I am not concentrating on what I am doing, I can type very quickly and accurately, but as soon as I think about it, where the keys are, for example, I type like a fool, extremely slowly and with numerous errors. The same applies to plenty of other activities, such as playing the piano, driving a car, even reading and talking. If you think about what you are doing you do it less efficiently. Why?

Lucy Kaye

London, UK

This observation is certainly correct and can be seen in controlled laboratory conditions. However, the reasons for it are not clear.

My speculation would be that the difference when doing something automatically, rather than thinking about it, is similar to the difference between parallel and sequential processing in a computer. With parallel processing we can take account of a variety of things at the same time. But when we think about what we are doing, akin to serial processing, we can only attend to very few aspects of the task. We may even attend to the wrong ones.

However, this leaves us with the mystery of why thinking about what we are doing is often beneficial. If it wasn’t, we wouldn’t do it. This could be because thinking about what we are doing is the only way to do something novel before the automatic processes have been learned.

Chris Frith

Wellcome Trust Centre for Neuroimaging

University College London, UK

Having recently gained weight, I’ve found that areas of my body where fat has deposited become cold to touch more quickly than those with less fat. Why is this?

Katherine Helmetag

Troy, Michigan, US

To put it simply, fat is an insulator. In the same way that walls insulate a home, fat decreases the rate of thermal loss so its outside edge feels cooler. If you touch a person wearing a winter jacket, you will find it is cooler than their skin.

M. Sjolander

Ankarsvik, Sweden

When ambient temperature is lower than that of the body, the temperature of the skin depends on the balance between the amount of heat reaching the skin, either via warm arterial blood or by direct conduction from underlying tissues, and the amount of heat leaving the skin to the environment.

When we get cold, blood vessels under the skin close up, reducing the delivery of heat to the skin by arterial blood. The skin is then kept warm by heat conduction alone. Fat, or adipose tissue, is a better insulator than lean tissue because it contains less water. Thus any skin above adipose tissue will receive less heat, making it cooler than the skin over lean tissue.

Many animals, especially marine animals, exploit this property of adipose tissue by having a thick layer of subcutaneous fat. When these animals need to conserve heat, the blood vessels below the surface close, as in people, and the thick insulating layer of fat minimises heat conduction to the skin. When heat dissipation is needed, during exercise for example, the flow of arterial blood to the skin is increased, effectively bypassing the subcutaneous insulation.

Shane Maloney

School of Biomedical and Chemical Science

University of Western Australia, Perth

Why does one really seem to feel the emotional response known colloquially as a ‘broken heart’ in the middle of one’s chest; indeed actually in the region of the heart?

Mark Collen

Sacramento, California, US

A metaphor offers a clue: the Japanese emphasise the stomach rather than the heart. Also, in English we speak of ‘not having the stomach’ for something. In healthy people it is the muscular viscera that draw attention to themselves, particularly those of the heart, oesophagus and stomach. Though they are under involuntary nervous and hormonal control, their physical reactions give dramatic feedback.

The heart reflects emotions by the intensity and rhythm of its actions, for example in shock it leaps and pounds. Anxiety can cause actual stomach aches and ‘lump-in-throat’ oesophageal spasms.

Helplessness causes diastolic flaccidity - a drastic reduction in blood pressure - which may explain deaths in those who believe they are the subject of a voodoo curse. It could also explain the physical heartache of grief, loss or betrayal. In addition, it reduces circulation and causes cardiac irregularity or palpitations, with frightening symptoms such as faintness and tingling in the face and extremities.

Conversely, surges of adrenalin cause the pulse to race, which increases blood pressure for emergency exertion but can cause paralysing panic when one does not know what to do.

Compare this to the less muscular vital organs which cannot give such immediate feedback - it takes time to interpret what the liver or kidneys have to say.

Antony David

London, UK

The eye views images upside-down in the manner of a camera lens, but our brains reinterpret this input to allow us to see things the correct way up. Have there been any examples of damage to this part of the brain, causing people to see the world upside down? How does this happen, is the brain able to compensate and, if so, how?

Kel

Gladesville, New South Wales, Australia

There is no example of damage to the brain causing people to see the world upside-down. This is because the image itself doesn’t actually transfer directly to your brain; only a series of electrical signals is carried there.

The lens of the eye does focus an upside-down image onto the retina. This image is then translated into a series of electrical signals which travel down the optic nerve and pass through the lateral geniculate nucleus - a kind of way station - into the occipital (visual) cortex at the back of the brain.

The reason that the upside-down image does not get flipped is because there is no image to flip. In your brain there are only electrical signals being sent from neuron to neuron, transforming as they go. Your brain processes these signals to create your experience of sight.

Experiments show that if imagery received by the eyes is inverted for a long time, these signals are simply reinterpreted by the brain and eventually perceived as the right way up.

Gregory Szucs

North York, Ontario, Canada

The brain does not need any special mechanism to compensate for the image in the eye being upside-down. Once the retina has converted the image into neural information, the physical arrangement of the information is arbitrary.

For example, why should it matter to the brain cells dealing with the top half of the visual world that the nerves supplying them with information happen to originate in the bottom half of the retina?

Tim McCulloch

Camperdown, New South Wales, Australia

As a child, I remember constructing a pinhole lens using toilet-paper rolls and tissue paper as the screens. I placed it against one eye and covered my other eye. These lenses invert the image of the world, and initially it was very disorienting seeing everything upside-down: I walked into doors and collided with any number of household objects. However, tactile feedback is a good teacher, and I learned to cope with it. After some time, my brain adapted and the image I was perceiving reverted back to normal. Then, of course, once I had adapted, taking the lens off caused everything to flip upside-down again, until I readjusted once more.

I guess that the ability of the brain to cope with an inverted view of the world would be similar to coping with a mirrorimage view: at first, trying to correctly position something while looking in a mirror is very difficult, but with practice it becomes instinctual.

Simon Iveson

Warabrook, New South Wales, Australia

It is generally known that our eyes form an inverted image of what we see and that the brain corrects the scene to look the right way up. However, when people wear inverting spectacles so that a scene is inverted before it enters our eyes, the wearer should see the world inverted. George Malcolm Stratton did this experiment in 1897 and claimed that the world looked the right way up again within a week. In other words, the brain ‘reinstated’ the upright vision.

The experiment has been repeated a few times since, with mixed results, so the jury is still out on this claim. Experiments in the 1940s and 1950s showed that human subjects managed to ride bikes and to go skiing while wearing inverting spectacles, suggesting that they were seeing the world the right way up. However, in the late 1990s a team led by David Linden refuted this claim in Perception (vol. 19, p. 469). Their paper suggests that those wearing inverting spectacles simply adapt to seeing the world upside-down by learning new motor patterns and increasing their skill at spatial transformations.

Mike Follows

Willenhall, West Midlands, UK

Why do we grimace when we eat sour or bitter food?

Laura Offer

London, UK

The body has stereotyped sequences of action for avoiding and responding to noxious stimuli such as pungency and acidity. Some resemble involuntary defences against physical attack and are similar through most of the animal kingdom, so they are almost certainly primitive in origin.

In humans, a faceful of ammonia or acetic acid fumes causes retreat, closed eyes and arms thrown across the face, among other responses. A noxious mouthful of a salty, bitter, acidic or otherwise vile chemical that our species instinctively avoids, such as one’s own ordure, causes another range of reactions, related to spitting or vomiting. Typical responses include: drawing down the corners of the mouth or gagging in preparation to vomit; salivating to clear the mouth and dilute harmful substances; puckering to avoid more intake; closing the eyes for protection; and performing convulsions that would help free oneself from assault.

More trivial stimulation - for instance, from piquant foods like pickles or mustard - provokes milder incipient reactions such as grimaces and shuddering. Perhaps the reason these different levels of reaction have survived and become entrenched is that such behaviour has evolved into a warning to offspring and associates: ‘Bad stuff! Beware!’ These less vigorous communication signals evolved more recently than the primitive reactions, and accordingly vary more widely between species, but they serve the same functions: warning of danger or nastiness, or indicating good feeding.

Jon Richfield

Somerset West, South Africa

Driving along in the car the other day, my four-year-old son asked why things that were closer to us were moving faster than those further away. What should I tell him?

Milton Inverdale

London, UK

Thanks for a vast number of answers to this question, many of which were probably more suited to undergraduate level than to a four-year-old. However, one notable group of wags insisted on sidestepping the answer at all costs. Among these was the inevitable ‘Ask your mother’, from Tony Turner of Tuross Head, New South Wales, Australia. Stephen McIntosh of Hull, UK, suggested: ‘You are far too intelligent for a four-year-old… have a lolly.’ More encouraging was the answer from Dave Oldham of Northampton, UK, who offered: ‘If you can ask a question like that at four years of age it won’t be many more years before you can explain it to me.’ And congratulations to Peter Gosling of Farnham, Surrey, UK, for his unashamedly literal view of the world. His advice was: ‘I think you should tell your son that it is illegal for him to be driving at four years old.’ - Ed.

When my son was a similar age, I tried to explain this phenomenon during a train journey. First I pointed out that objects further away look smaller. I used his hands to show this: if he held one hand close to his face and the other at arm’s length, the one at arm’s length appeared smaller, even though he could put his hands together to confirm they were the same size.

Secondly, I showed him that it takes more objects to fill the same amount of visual space if they are further away. For example, if the hand further away is half the apparent width of the one closer, it takes two hands to fill the same width.

Finally, I got him to think about something moving, such as an index finger traced slowly from one side of his palm to the other. If it moved at the same speed when it was further away, it travelled the same actual distance (a palm’s width), but seemed to have travelled only half as far. So it would take twice as long for it to look like it had travelled the same distance. I then summed up by explaining that the distant things were not actually moving slower, they just looked as if they were.

I also had to explain why it looked as if the trees and houses were moving when my son was sure that they weren’t really. First, I got him to move his hand in front of his face, and then to hold his hand still but move his head from side to side. In each case he could see that the hand seemed to move across his vision in the same way. I told him that the two movements were equivalent and he seemed to accept that.

The other passengers on the train thought I was a little strange, but it kept my son quiet.

Keri Harthoorn

Stoke-on-Trent, Staffordshire, UK

The answer is that the type of optical system that is used by our eyes causes us to perceive a particular object as ‘smaller’ the more distant it is - a phenomenon called foreshortening. As our vision system converts the angles subtended by the things we are looking at into apparent distances on our retina, this causes nearby objects to sweep through our field of vision much more rapidly than distant ones. So while distant and nearby objects are within the same field of vision, those further away take longer to pass across it, as they have a low angular velocity, than those that are closer.

You can demonstrate this by placing your hand on a newspaper. Make a ‘V’ with your index and middle fingers and sweep it along the text. Your hand is the car, and the V is your field of view. You can see that the text near your fingernails takes a long time to move from one finger to the next, while the text closer to your hand moves more rapidly.

Gregg Favalora

Arlington, Massachusetts, US

One way to demonstrate this process is to put a toy car on a path representing the road, with an object placed 30 centimetres ahead and 30 centimetres to the side of it. Show your son how the object goes from being diagonally ahead to diagonally behind the toy car when you move it forward 60 centimetres. Then do the same thing, but with the object 3 metres ahead and 3 metres to the side. This time the car has to travel 6 metres to cause the same change in the angle at which someone in the car would view it. Also point out that it takes much longer for the car to travel 6 metres as for it to travel only 60 centimetres.

Eric Kvaalen

La Courneuve, France

What is the storage capacity of the human brain in gigabytes? If we were to construct a PC with similar computational power to our brain, what would its technical specifications need to be?

John Gladstone

Southampton, UK

We can only answer this question if we assume the human brain is like a computer. For example, if each neuron holds 1 bit of information then the brain could hold about 4 terabytes (4,000 gigabytes).

However, each neuron might hold more than 1 bit if we consider that information could be held at the level of the synapses through which one neuron connects to another. There are about 50,000 synapses per neuron. On this basis, the storage capacity could be 500 terabytes or more. But these are perhaps misleading answers because the human brain is not like a standard computer. First, it operates in parallel rather than serially. Second, it uses all sorts of data-compression routines. And third, it can create more storage capacity by generating new synapses and even new neurons.

The brain has many limitations, but storage capacity is not one. The problem is getting the stuff in and, even more problematic, getting the stuff out again. We can demonstrate that storage capacity is not the problem if we consider the technique experts use to remember the order of a shuffled pack of cards. This technique, called the ‘method of loci’, goes back to classical antiquity. It involves imagining a journey in which each card appears at a certain location.

Here is an example that I found on the internet: the first card is an 8 of clubs. To memorise this you imagine going out of your front door, the first step on the journey, and finding your path blocked by a person smashing an egg timer (which is shaped like an 8) to pieces with a mallet (a club). The next card is then placed on the next step of the journey with an equally vivid image.

What is striking about this technique is that the story you create to remember the order of the pack of cards contains much more information than the simple pack of cards you are trying to remember. The vivid images are necessary to get the information into our brain and to get it out again later.

Chris Frith

Wellcome Trust Centre for Neuroimaging

University College London, UK

What would happen if a man took the contraceptive pill, either once, accidentally, or daily? Are there any published cases?

Arnout Jaspers

Leiden, Netherlands

If he took it only once, probably nothing would happen, except perhaps side effects such as nausea. As for regular, long-term use, the effects would depend on the type of pill he took: combined or progestogen-only.

The combined pill contains oestrogens, which are responsible for the development of female secondary sexual characteristics, so a combined pill would cause slow changes in some body features that would vary from man to man.

The first changes would probably be visible within two to three months. The man’s breasts would start to grow, with his nipples becoming larger. His skin would become thinner and softer, which would lead to change in skin tone - pink, with the veins more visible. Body fat would start accumulating in ‘female areas’, such as under facial skin - making his face look puffier - and also around his hips, thighs, upper arms and pubis.

More significant changes, such as a slimmer waist-to-hips ratio and fleshier hips and buttocks, would probably take many more months to develop. His muscles might become thinner, and his body and scalp hair might change in texture, but the pill alone would not inhibit the growth of facial hair or improve male pattern baldness. Sweat production would also change, as would the body odours of skin, sweat and urine, which would become less sharp and more sweet and musky.

The pill-taker would notice some emotional changes too, such as a greater tendency towards mood swings or depression. Recent studies have indicated that cross-hormone therapy in male-to-female transsexual people may result in a reduction in the volume of the brain towards female proportions - but with no effect on IQ. Regular intake of oestrogens would also increase the risk of blood clotting, decrease insulin sensitivity and cause disturbances in liver function.

By contrast, the hormones in the progestogen-only pill do not cause feminisation in a male. Some studies show that they act like anti-androgens and would probably suppress testosterone to some degree, causing breast growth and a decrease in facial hair. This pill might raise the taker’s body temperature and cause fluid retention.

I could not find any clinical studies, but it seems certain that some will have been done, because oral contraceptives have been widely used in gender reassignment for men who want to become women.

Joanna Jastrzebska

North Shields, Tyne and Wear, UK

I was a guinea pig for a trial a few years back which involved exactly this, as part of research into a male contraceptive pill. The trial lasted one week, during which some of us were given a common oral contraceptive but at four times the dose prescribed to women, while others were given the same quantity of the same hormones by injection. I was in the second group.

The first day I didn’t notice much difference, so I assume a man taking a single pill would be unaffected. The second day, I felt a little down and emotional. My libido started to diminish. On the third day, I was tearful.

I don’t know what happened to my testosterone levels, but I wasn’t interested in going to the gym any more. More than usual, I wanted to eat chocolate and chat to my female friends. Yes, I am being serious. Little things like events in a movie would start me crying. This stabilised at around the fourth day. On the seventh day I took the last dose of hormone and the effects wore off within a couple more days. The doctor in charge assured me there would be no lasting changes.

All in all, I feel I’ve had an insight into what it feels like to be a woman. I suspect that it would certainly work as a contraceptive (beyond its chemical effect) because I had no interest in sex, but I doubt many men would want to take female hormones at the expense of their ‘manliness’. It was an interesting experience, but not one I wish to repeat.

R. Ross

Aberdeen, UK

Readers have often contacted us to ask whether there is anything Jon Richfield - a prolific answerer of questions from these books - does not know. Well, it seems there is - Ed.

This is a question that my husband, Jon Richfield, cannot answer to my satisfaction. I find the taste of certain common spices quite horrible. The nasty flavour I get from all of them seems, to me, quite similar. The spices that taste this way are aniseed, caraway, cumin, fennel and coriander. Tarragon, cardamom and capers also taste awful in the same way. I wonder if there is a food scientist who knows what they have in common, or what my aversion might be. I should add that I am not a fussy eater in general.

Bess Richfield

Somerset West, South Africa

The substance that your correspondent finds foul-tasting is probably a terpenoid called carvone. This chemical provides the principal flavour of caraway seed and, by itself, has a typical caraway flavour.

All the spices she mentions are members of the Umbelliferae family, and all of them contain this substance. Carvone is also found in tarragon, cardamom and capers.

Ralph Hancock

London, UK

I heard once, but have not verified myself, that there is a cis-trans isomerism (the orientation of groups of atoms and the positions they occupy within molecules) in the taste buds of some people which binds to at least one of the flavour components of cilantro, the leaf part of coriander.

For most people, the taste is pleasant. For those with the other isomeric version of the taste bud’s active site, however, the taste is more like soap. If this theory is correct it could extend to the flavour experience of the other spices such as aniseed and caraway.

Karen Nyhus

San Francisco, California, US

One explanation for the perverted taste sensations with some spices is that your correspondent suffers from mild zinc deficiency. This gives rise to hypogeusia, or altered taste, usually for the worse. It would be interesting to find out if taking zinc sulphate tablets, under the direction of a doctor, for four weeks would make a difference.

Tim Healey

Barnsley, South Yorkshire, UK

The first time I had two pints of beer in my late teens I was horribly sick. Now I can drink two pints of beer without feeling any ill effects. What is the mechanism by which our bodies become tolerant to alcohol, or indeed other drugs, all of which have a smaller and smaller effect with regular use? After all, I am consuming exactly the same amount of poison which made me ill 30 years ago - why doesn’t my body just do what it did back then?

Rob Howe

Gomersal, West Yorkshire, UK

The ethanol in alcoholic drinks is metabolised almost exclusively by the liver. The liver enzymes responsible are alcohol dehydrogenase (ADH), catalase and an enzyme complex known as the microsomal ethanol-oxidising system (MEOS). Repeated administration of alcohol will increase the amount of these liver enzymes, and subsequently improve its ability to metabolise alcohol.

However, such enzyme induction does not fully account for improved alcohol tolerance. There is also a mechanism of behavioural tolerance whereby an individual learns to function under the influence of alcohol.

Finally, you are probably larger now than when you were in your late teens. This means that your total blood volume is also likely to be increased, so although two pints of beer will contain the same mass of alcohol, it will be at a lower concentration in your blood.

Benjamin Hunt

Leicester, UK

One explanation for the development of tolerance stems from a 2004 study at the University of Texas into fruit flies’ response to benzyl alcohol. As the fruit flies developed tolerance to the alcohol, researchers noted an increased activity in their slo gene. Slo modulates a cell-surface protein, helping to increase signalling between nerve cells in the brain. Under sedation from alcohol, the activity of the fruit flies’ slo gene doubled.

The protein acts almost as a thermostat would. For example, if a drug other than alcohol excites the nervous system and increases signalling, slo gene activity decreases, which suppresses the effects of the drug. Conversely, alcohol suppresses the nervous system and slo activity increases, serving to counteract the sedative effects of alcohol by stimulating signalling.

Previous exposure to a drug enhanced the future performance of slo in the fruit flies, meaning it becomes more responsive and better able to suppress the effects of a drug.

The slo gene found in fruit flies is very similar to the human version. The performance of the questioner’s genetic thermostat will have improved after 30 years of practice, and therefore more pints are required.

Jeremy Fancher

University City, Missouri, US

How many people are cremated each year and how much energy is consumed in the process? Will these numbers increase on current projections? And are there no better and more environmentally friendly methods of disposal?

Jeremy Dawson

Laurencekirk, Grampian, UK

Cremation is the accepted practice for disposing of dead bodies for a number of religious groups in India, including Hindus, Sikhs, Buddhists and Jains. Some 85 per cent of the country’s 1-billion-plus population cremate their dead. Beyond the Indian subcontinent, Hinduism is also a significant religion in Mauritius, Guyana and Fiji.

Many people from other religions, including Taoism and Shinto practised in China, Japan and Indo-China, also choose to cremate their dead. Cremation is not just limited to religious custom; it is also practised by many people in Europe and America for reasons other than religion.

A conservative estimate for the number of people around the world who would opt for cremation is around 1.2 billion. Taking an annual death rate of 1.5 per cent, that means roughly 18 million cremations annually.

It takes about 100 kilograms of wood to create a fire that is hot enough to cremate an average human body, so that adds up to 1.8 million tonnes of wood. If we take the energy value of wood as 17 megajoules per kilogram, this works out at about 30 million gigajoules.

In some places, electric furnaces replace wood. These tend to have a capacity of between 75 and 100 kilowatts, and they can cremate a body in 30 minutes or so, consuming somewhere between 0.13 and 0.18 megajoules for each body.

However, most bodies worldwide are simply buried. Coffins consume wood, of course, and the quantity can be substantial in prosperous western societies.

There are many factors to consider regarding the environmental impact of these various practices. While cremation consumes wood and generates smoke and carbon dioxide, burial also generates carbon dioxide, methane and other substances as bodies decompose, although this is spread over a longer time period.

In addition, burial also occupies land, and in some societies such land is considered sacred and so cannot be used again. At one time, families in China reserved the most fertile patch of their farmland for burials, thus blocking land use forever.

Apart from burial and cremation, there are some unusual practices in some parts of the world. Some Tibetans hack up bodies and feed the pieces to vultures. In India and Iran, Zoroastrians also allow their dead to be consumed by vultures, placing the bodies on a circular structure called a tower of silence. Tibetans and Zoroastrians believe that the body should serve a useful purpose after death - and the environmental impact is zero. Burial at sea, as practised by sailors, also works in the same way, although the motives are more practical.

Some people in other societies have the same thought regarding usefulness when they donate their bodies to medical research. However, the remains have to be disposed of later, normally by incineration.

Dileep Paranjpye

Lucknow, India

The most recently available global figures for cremation are from 2006 and they put the figure at 7,838,353. As with most global statistics, the heavyweights are China, which cremates more than 4 million people a year. In places with little spare land, such as Japan, nearly everyone is cremated, while in the US only 33 per cent of people are. These figures are likely to increase as the Catholic population becomes more comfortable with cremation.

Calculating the amount of energy used in cremations worldwide is nearly impossible because of differences in fuel types and costings.

Cremation is, of course, becoming untenable. The gas used is a fossil fuel creating heat and pollution, and the vapours emitted, despite increasingly sophisticated and expensive filters, release toxins such as mercury.

Susanne Wiigh Masak, a Swedish biologist and keen gardener, has invented a process she calls Promessa, in which liquid nitrogen is used to freeze-dry bodies into what she describes as a perfect compost.

Another alternative, marketed by Sandy Sullivan, is called Resomation. This is a form of speeded-up anaerobic digestion using heated alkalines. Both are hugely improved methods of disposal, which have interesting possible environmental applications. The major obstacle is, of course, the squeamishness of the public.

The most environmentally sound method of cremation is on an open-air pyre using wood. Not only would this be carbon neutral, but it would be much more spiritually and psychologically nourishing than the current industrial conveyor-belt approach that is used in most modern crematoriums. It is my company’s most-requested ‘fantasy funeral’.

Rupert Callender

The Green Funeral Company

Dartington Hall Estate, Devon, UK

Why, after I’ve spent hours attempting to remember somebody’s name or something similar, does the answer eventually arrive in the middle of the night when I’m not even trying?

Ben Longstaff

London, UK

It has been suggested that when someone has this kind of sudden insight (an ‘aha!’ moment), one’s mind has taken unconscious ‘pathways’ that have led to the solution of the problem - whether it’s your cousin’s boyfriend’s name or 5-down in the crossword you attempted yesterday.

It seems that the first time you were trying to remember that name, however, your mind activated the wrong pathway. That misdirected activation might have been stronger than the answer-related activation, masking the latter, even though you knew the answer. Only when the former subsides can the solution-related activation surpass the threshold of consciousness and be perceived. It might happen when you’re not expecting it, like just before sleeping. More information on these processes can be found in a Psyconomic Bulletin and Review article published in 2003 (vol. 10, p. 730).

Dilza Campos

Rio de Janeiro, Brazil

Just because the conscious mind is not focused on recalling a name does not mean the brain is not churning away at the problem, even during sleep. Indeed, as a designer I have learned to trust this non-conscious, problem-solving process. Upon retiring, I will often select some difficult, unsolved design dilemma from a current project and ‘assign’ it to myself. When I awake in the morning, almost invariably I will discover that I have worked out a solution.

Many older people - myself among them - whose memories may be increasingly cluttered and whose recall mechanisms may be slower, discover that precisely by not trying to recall a name or term but merely waiting or continuing with another thought or activity, the sought-after memory comes to them of its own accord.

Larry Constantine

Department of Mathematics and Engineering

University of Madeira

Funchal, Portugal

When closely matched athletes are competing in events that involve running, swimming, throwing or lifting, why does one of them win one day and another the next? Surely whoever is the fastest or strongest will remain so, for a while at least. Often the original winner will return a few days later and win again, so why did he or she lose the race between the two victories?

Magda Loncic

Kiev, Ukraine

The questioner must not belong to a gym. If you regularly take exercise in a quantifiable way, you soon notice that there are ‘strong’ days and ‘weak’ days. The most obvious factors influencing these are the amount and quality of sleep achieved beforehand, and how one is nourished. Elite athletes may eliminate variation in their food intake on race days, and may even manage to regularise their sleep schedules, but one or another may be fighting off a minor viral infection, or the temperature or humidity may be more to one’s liking than to another’s.

Steve Gisselbrecht

Boston, Massachusetts, US

The answer to this question lies in another question within the query: how closely matched are the athletes?

If the athletes were identical in skill, strength, speed and motivation, presumably they would never beat one another. But they do, because there are always factors both innate and environmental that interfere.

Nowadays most athletic events that involve covering a distance are timed to one-thousandth of a second, so any competitor who beats another by less than this margin is declared to have equalled the other’s time. That is extremely unlikely, so in fact there is almost always a winner and a loser.

At a more macro level, the environment, plus the athletes’ mental and physical states, are likely to vary by more than, say, 0.1 per cent and this makes all the difference at the elite level. When you add in diet, will to win, fit of shoes, distance from starting gun and such like, it’s surprising there are any dead heats at all.

Mike Rennie

Professor of Clinical Physiology

University of Nottingham Medical School

Derby, UK

An athlete’s form reflects many different and constantly varying factors, any of which could prevent a win if overdone, underdone, or done in the wrong combination.

Whether psychological or physiological, any changes in the body’s status will take time to resolve, causing cyclical or quasi-cyclical performance as they do. Effective coaches try to time the optimum for the day of performance and the optima may be brief, sometimes ended by the reaction to victory itself - for example, through overconfidence or a lapse in commitment.

Athletes don’t perform according to fixed standards of precision like machine tools. The bell curve, or normal distribution, is ubiquitous. It describes the statistical variability of any athlete’s performance and of differences between athletes. Each component variable has its own normal curve, and how they combine affects the athlete’s overall variability. Different athletes’ curves of variation can overlap far enough to reverse the outcomes of competitions dramatically.

Some variation in form is unpredictable, such as injury, illness, personal events, psyching or luck on the day. Other effects are systematic, such as maturing, declining or cumulative stress, whether mental or physical. Any of those could cause gradual eclipse; almost any could cause sudden loss of form, even mid-game, and most setbacks are at least temporarily reversible.

Jon Richfield

Somerset West, South Africa

How do traditional Inuit avoid scurvy?

Thom Osborne

Granada, Spain

Humans - along with other primates, guinea pigs and fruit bats - cannot produce their own vitamin C and so need to get at least 10 milligrams per day from their diet to stay healthy. A deficiency results in scurvy, but it can take several weeks or months before the body shows signs of the disease - starting with bleeding gums and progressing to death if left untreated.

The Inuit avoid scurvy as they, too, get all the vitamin C they need from their diet, especially from eating raw meat. Muktuk - a mixture of frozen whale skin and blubber - is the richest source: 100 grams of muktuk yields 36 milligrams of vitamin C. Weight for weight, this is as good as orange juice. Raw caribou, kelp and more whale skin also provide more than enough vitamin C. The Inuit practice of freezing any food that is not eaten raw helps to conserve vitamins, in contrast to cooking food, which destroys vitamins.

Mike Follows

Willenhall, West Midlands, UK

I’ve just seen a sword-swallowing act. Swords that were seemingly longer than the depth from throat to anus were swallowed. It has to be a trick, doesn’t it? If it is, what’s the trick? If it isn’t, what’s going on?

Alan Finnegan

Whitehaven, Cumbria, UK

The taller you are the more sword you can swallow, but it cannot go past the pit of the stomach. And that is one thing that sword swallowers have to get used to - the feeling as the point of the sword arrives there… just touching, and no more. This is why some swallowers eat heavy food just before performing, to stretch the stomach a bit so they can swallow a longer sword.

The other thing they have to get used to is the gagging reflex when they start to swallow. This can be controlled eventually.

Swallowers use silk to clean the sword just before it’s inserted to remove any dust, and again while the sword is being withdrawn (with a great flourish of silk) to clean off acid stomach juices that can attack the steel. It’s all a matter of skill and nerve, with little room for trickery.

For the best account of this and more, including swallowing giant corkscrews that make the pharynx jump up and down as they twist; how to swallow neon tubes to make the chest glow from inside; and how to eat and swallow fire (when learning, have a lot of ice cream handy), can be found in Memoirs of a Sword Swallower, by Dan Mannix, first published in 1951, which is when I bought my copy. I’ll never forget that opening sentence: ‘I probably never would have become America’s leading fire-eater if Flamo the Great hadn’t happened to explode that night in front of Krinko’s Great Combined Carnival Side Shows.’

Michael Boddy

Binalong, New South Wales, Australia

There is no trick to a genuine sword-swallowing act, or rather not the kind of trick your correspondent is probably thinking of. Strictly speaking, a true sword swallower doesn’t actually swallow the sword, but that apparent contradiction is the key to how the swallower actually manages to get the blade all the way down.

To join the Sword Swallower’s Association International, a would-be member has to demonstrate the ability to ‘swallow’ a non-retractable, solid steel blade that is at least 2 centimetres wide and 38 cm long. With those qualifications, it’s not really surprising that the current worldwide membership of the SSAI is restricted to a few dozen full-time professionals and a handful of amateurs. Nor is it a surprise that, despite the SSAI’s strict membership criteria, many people believe a trick blade is employed, particularly when one learns that the record length for a swallowed blade is an eye-watering 82.5 cm.

The performer, through a regime of practice, learns to suppress the natural gag instinct, by relaxing the upper oesophageal sphincter - which normally closes the throat to prevent us choking or drowning. To do this, they usually start by forcing their fingers down their throat and then work their way through a range of longer and bulkier everyday objects, before regularly exercising with a carefully folded wire coat hanger.

Curiously, in sword swallowing, as in so many other aspects of life, size apparently doesn’t matter. Although the artiste who swallowed the aforementioned 82.5-cm sword was 220 cm tall, it is the configuration of a performer’s insides that determines the length of blade they can swallow. Particularly critical is the angle of the gastro-oesophageal junction, or cardia - the point where the oesophagus joins the stomach.

The cardia is where the lower oesophageal sphincter is found. This sphincter prevents gastric juices flowing up out of the stomach into the throat. It is the ability to exercise control over this valve, and keep it relaxed when it should, by reflex, close, that is critical for a performer.

It is scarcely surprising that industrial injuries among sword swallowers produce a distinctive pathology. While no member of the SSAI has died as a result of a performance going awry, at least one sword swallower has brushed the side of his heart with a blade, and perforations and lacerations of both the oesophagus and pharynx are common, as are lower chest pains. These pains are often associated with a dramatic technique known as ‘the drop’, where the sword is downed in one smooth action, controlled only by the muscles of the pharynx.

The most widespread occupational hazard suffered by sword swallowers is a sore throat - ‘sword throat’, as it is known. At least one swallower had to terminate their career through losing the ability to salivate, as saliva is the principal lubricant employed to ease the passage of the blade (although butter has been used as a substitute).

Of course, this is an experiment that would-be researchers should never, ever attempt at home.

Hadrian Jeffs

Norwich, Norfolk, UK

In February 2010 Australian performance artist Chayne Hultgren, also known by his stage name The Space Cowboy, set a new world record by simultaneously swallowing 18 swords, each nearly 75 centimetres long. ‘Wow, I did it, it feels good, thank you very much, it feels really good actually,’ he said after setting the record. We still suggest readers don’t follow his example - Ed.

Why is it that when I get into a bath at 39 °C I feel totally relaxed and yet, when I enter a room at the same temperature, I feel totally stressed?

Alan Parr

Corwen, Clwyd, UK

Although the bath may be at 39 °C, the air in the bathroom is probably much colder, allowing part of the body to lose excess heat. This heat loss is helped by evaporation of the bath water. In contrast, when the air in a room is at 39 °C, heat will be flowing into one’s body, rather than away, and body temperature will begin to increase. Since the body then has to lose excess heat, the feeling of stress goads the brain into taking action, such as drinking a cold drink or moving to a cooler room.

Keith Lawrence

Staines, Middlesex, UK

Why do people say ‘um’ and ‘er’ when hesitating in their speech?

Michael Larcombe

Belper, Derbyshire, UK

This question can actually be split into two: why do people say anything at all while hesitating and why do they say ‘er’ and ‘um’ instead of other possible sounds?

To answer the first question, linguists known as conversation analysts have observed that people vocalise in a conversation when they think it is their turn to talk, and there are several ways of negotiating the taking of those turns. One of them is the relinquishing of a turn by the current speaker and another speaker taking the floor. Therefore, silence is often construed as a signal that the current speaker is ready to give up his or her turn.

So, if we wish to continue our speaking turn, we often need to fill the silences with a sound to show that we intend to carry on speaking. If we always thought out thoroughly everything we were going to say in a conversation, or memorised our lines perfectly, there would be no hesitation at all.

But, as it is, we do a lot of what is called local management, or improvisation, during conversation for many reasons - not least because we cannot predict the reactions of our interlocutor. In order to keep the floor while we hesitate, we place dummy words in the empty spaces between our words, much as we might drape our coats on a seat at the cinema to prevent others from taking it.

The second question, as to why ‘er’ and ‘um’ are used instead of, say, ‘ee’ or ‘choo’, is not as easy to answer. ‘Er’ in British English is a transcription of the phonetic ‘schwa’ sound found in unstressed syllables of English words (such as the vowel sound in the first syllable of ‘potato’).

In traditional phonetics this was called the neutral sound because it is the vowel sound produced when the mouth is not in gear, that is, not tensed to say any of the other formed vowels such as ‘e’.

The ‘um’ sound is more difficult to explain unless it is just a bad transcription of the same neutral sound with a consonant that closes the mouth in preparation for another real word.

By the way, these sounds are not universal. Many speakers of other languages hesitate in other ways. In Latin languages, for example, the pure sound of the vowel ‘e’ is often used.

William DeFelice

Barcelona, Spain

‘Er’ is used as a conversation filler because it is the most easily pronounced voiced sound for an Anglophone. This is shown easily in a stress-timed language such as English in which all unstressed vowel sounds tend towards the central vowel position.

It is known as the central vowel position because it is pronounced in the centre of the mouth, irrespective of the written vowel, as in ‘America’, ‘trousers’, ‘ferocious, prospective’, ‘purpose’. ‘Um’ is really only ‘er’ with a closed mouth, as can be shown empirically.

English-speaking pupils learning foreign languages have a tendency to ‘um’ and ‘er’ in a way which is quite foreign to native speakers of the target language. It is also the case that using the correct alternatives gives an impression of fluency greater than that shown by pupils who avoid such utterances, but whose pronunciation is almost flawless.

John Gillespie

Modern Languages Department

Glenalmond College

Perth, UK

‘Um’ and ‘er’ are culturally determined. For example, Mandarin Chinese speakers often say ‘zhege zhege zhege’ (this this this). Some young, hip foreigners learning Mandarin soon ‘zhege zhege zhege’ with the best of them.

Kevin McCready

Wamboin, New South Wales, Australia

People don’t say ‘um’ and ‘er’ any more. Instead, they say ‘basically …’

R. J. Isaacs

Barnet, Hertfordshire, UK

Even ‘basically’ has been superseded by the latest teen speak. It’s not ‘um’ or ‘er’, it’s ‘I was like, omigod, that’s like so totally not good…’

Fluttering your hands in front of your face as if to cool yourself down at this point is, like, a totally optional extra.

Natalie Henwick

London, UK

Ever since the recent birth of my son, who I breastfeed, I have wondered why men have nipples.

Dorthe Mindorf

Aalborg, Denmark

Many suggestions for this phenomenon have been offered. They may exist to help men check that their vests are on straight, or be present as a safety feature - to warn us how far out from the beach we can safely wade.

However, there is a more plausible explanation. Male and female human embryos are identical in the early stages of their development. If the fetus receives a Y chromosome from its father, a hormonal signal is produced: the labia fuse to form a scrotum, the gonads develop as testicles and a male results. Otherwise the ‘default’ female remains.

Various structures in the adult reflect the symmetry of male and female and their common embryonic source. Men have nipples because they have already begun to develop when the ‘switch to male’ signal is received. The development of breasts is halted in most - but not all - cases but the nipples are not reabsorbed.

Another effect of these developmental pathways which are shared by both males and females is pointed out in Stephen Jay Gould’s essay ‘Male Nipples and Clitoral Ripples’ (which can be found in the Penguin Books’ 60th anniversary collection, Adam’s Navel). Males need plenty of blood vessels and nerve endings in their penises to achieve erections. Because the penis and clitoris have their origins in the same structure, females have the same number of blood vessels and nerve endings packed into a much smaller area, resulting in the enhanced sensitivity of the clitoris.

Conclusive evidence that God is not a man?

Jim Endersby

University of New South Wales

Sydney, Australia

What is it about loud rock music that makes your ears ring after several hours at a concert or club? Does loud classical music have the same effect?

Rebecca Wiseman

London, UK

… er, pardon?

Dave Walters

Broadcast Engineer

Classic FM, London, UK

Ringing in the ears is called tinnitus. In the circumstances described above it can often be accompanied by a temporary loss of hearing known as temporary threshold shift and indicates damage to the nerves of the inner ear caused by excessive noise exposure.

The criterion is not the type of music listened to but the sound energy involved. Rock music, being prone to electric amplification, can generate high noise levels. This tends not to be the case with classical music, with the possible exception of Wagner.

Repeated exposure to high noise levels can lead to permanent and irreversible hearing damage and because of this, noise in the workplace is subject to legislation - the maximum permitted exposure level being 90 dB(A) over an eight-hour shift.

Damage of this nature tends to affect hearing mainly at a frequency of about 4 kilohertz and presents a characteristic profile on an audiogram.

This loss is insidious and may not be noticeable to the sufferer until natural hearing loss through ageing (presbycusis) begins to occur. At this point, hearing function may start to drop off sharply and it is, unfortunately, far too late to do anything about it.

It is best not to expose one’s hearing to very high noise levels, but if it does occur, it is important to allow full recovery (16 hours) before re-exposure to the sound. You may wonder if rock musicians suffer from this form of deafness - they do.

Tom Croskery

Coleraine, Londonderry, UK

I know people who insist that certain types of alcoholic drinks put them in specific moods when drunk - such as emotional, violent or confident. Is there any scientific reason why different beverages would have specific effects on mood?

Frederick Allen

Oxford, UK

Unfortunately, there is no straightforward evidence to support this claim, nor is there any evidence against it. Whether you’re drinking wine, beer or spirits, the alcohol in your drink will be ethanol, which affects several neurotransmitters involved in determining mood. For example, alcohol inhibits glutamate receptors, which has the effect of relaxing muscles; it stimulates receptors that respond to gamma-aminobutyric acid (GABA), reducing anxiety; and it increases the release of dopamine, a hormone associated with excitement.

Mood and behaviour depend also on the degree of intoxication, which can be quantified by measuring the volume of alcohol in a given volume of blood, better known as the blood alcohol concentration (BAC). BAC depends not just on the amount of alcohol ingested but also on gender, weight and body fat.

When BAC is low (up to 0.06 per cent), the effects usually manifest themselves as euphoria, talkativeness and increased self-confidence. With BAC between 0.06 and 0.2 per cent, you will experience excitement and disinhibition, and then mood swings, particularly involving anger, boisterousness or sadness. The next stage, with BAC over 0.21 per cent, brings general inertia and a reduced response to stimuli. If you carry on drinking you will end up in a coma (BAC above 0.35 per cent) or even in the mortuary (above 0.50 per cent).

The context in which alcohol is consumed also plays a role. We tend to drink particular alcoholic beverages in particular situations: fine wine is usually savoured over a nice meal, for example, and hence is likely to put you in a mellow mood, while numerous shots of vodka may be consumed at a party on an empty stomach and will make you feel drunk much quicker.

Some people suggest that the mood you end up in when you drink depends on the mood you are in when you start, and that people tend to choose specific drinks for specific moods.

Joanna Jastrzebska

North Shields, Tyne and Wear, UK

I am fortunate enough to be able to wiggle my ears. However, I can only wiggle both at once, not one at a time. Why?

Peter Slessenger

Reading, Berkshire, UK

Bilateral symmetry is the default mode for movement. Infants suck, cry and wave their arms symmetrically and must eventually learn to do things one-sided. I have heard youngsters complain that they can’t wink: when they try, they close both eyes. Even as adults, it is easier to do mirror-writing with your left hand if you simultaneously write the same word with your right. I, too, could once wiggle my ears only both at once. With practice I learned to wiggle one at a time, an accomplishment of no value to anyone - until now.

Spencer Weart

Hastings-on-Hudson, New York, US

Some combined bodily actions share neural channels, which prevent independent action. It is hard, for example, to direct your eyes independently. Physically it should be possible, but your mental control specialises in binocular coordination.

As a rule, independent direction of sensory organs is suited to detecting prey or danger, while symmetrical sensing permits precise measurement.

Most primates use their ears to supplement binocular vision or for direction finding. This means that not many need to move their ears much and hardly any need to move them independently; instead they move their heads.

Correspondingly, visual ear signals such as twitching, vital to most carnivores and many herbivores, hardly figure in the social behaviour of primates, especially the anthropoids. Our legacy is generally symmetrical.

Jon Richfield

Somerset West, South Africa

In order to wiggle one ear at a time, practice is needed in front of a mirror. That is how I learned the art. By grinning forcefully and widely, the ears are made to move. If you concentrate on finding the muscles that move the ears, you can operate them without grimacing. Then practise moving each ear by itself. What use does this skill have? It impressed teenage girls, up to a point, and a by-product was the smoothing out of wrinkles on my forehead.

Brian Colless

Palmerston North, New Zealand

Why is it that when we are tired the blood vessels in our eyes are more visible?

Lucy Bennett

By email, no address supplied

Apart from causing droopy eyelids, sleepiness slows down blinking, a process which normally keeps the conjunctiva - the outer layer of the eye - moist and well lubricated with fluid from the tear ducts. Its drying out triggers mild inflammation. The more obvious effect is red eyes, a consequence of the dilation of the conjunctiva’s capillary blood vessels, which are usually invisible.

All this causes the eyes to become itchy, and rubbing them only makes things worse, as does a dry indoor atmosphere or smoke. Contact lenses become unbearable by this stage, and if they dry out, too, can cause painful scratching of the conjunctiva.

Other than trying to remember to blink more frequently or going to bed and having a good night’s sleep, going outdoors into cooler and moister air helps, as does the humid air from a warm shower (though remove contact lenses first).

The quick fix of resorting to eye drops to reduce the inflammation and then going straight back into a dry, smoky atmosphere would be a short-sighted approach (pun, of course, intended).

Jim Horne

Sleep Research Centre

Loughborough University

Leicestershire, UK

Why don’t adults enjoy dizziness like children do? When I was a kid, I remember thinking that adults were rather boring for not enjoying the feeling of dizziness like I did, and I vowed to always enjoy it. Now, as an adult, I can’t stand it - it makes me want to throw up. It seems many other adults feel the same way. Why is this? Does something change in us as we age?

Ivan V.

Mexico City, Mexico

I still remember my first - and so far last - trip to a fairground. I was 15 and vomited after a ride on a merry-go-round. I couldn’t understand why my brother, who is three years younger than me, stayed for another ride.

Children obviously enjoy the feeling of dizziness - just look at how roundabouts in parks and playgrounds are packed with youngsters. They need that stimulation to develop a healthy balance system, which is necessary to crawl, walk and keep their bodies upright, even on a rocking boat.

Our balance system is controlled by three senses cooperating in complex harmony. The vestibular system in our inner ear informs us about the position of our head; our eyes tell us how our body is located in relation to the external world; and proprioceptors - receptors in muscles and joints - help us to figure out how our body is positioned in space, which is particularly helpful if we cannot see. These elements mature at different rates.

The vestibular system is fully operational by the time a child has reached 6 months of age; proprioceptors need three or four years more. The development of the visual element is complete by around 16 years of age.

The sensation of dizziness and nausea following a spinning movement is similar to motion sickness - a result of the conflicting information our brain receives from the three elements mentioned above.

When our body is rotating at speed our vestibular system and proprioceptors can feel it, but our eyes can’t locate the horizon. Our brain is desperately trying to resolve this conflict and, because humans are primarily visual, it assumes that the other senses are hallucinating, probably because of intoxication. So the brain tries to get rid of the assumed poison by provoking vomiting.

It looks as if my brother’s balance system hadn’t fully matured at the time of our trip to the fairground, hence his brain wasn’t perceiving the sensory information as conflicting. Therefore, he could enjoy his ride on the merry-go-round while, unfortunately, his older sister could not.

Joanna Jastrzebska

North Shields, Tyne & Wear, UK

Since my 20s, I have drunk on average a bottle of wine a day. I’m 57. That’s 49 UK alcohol units a week. The UK’s recommended weekly limit for a man is 28 units. I recently had a health check at my local clinic, and I’m in perfect health. Specifically, my liver function tests are entirely normal. Am I exceptional or are the government limits spurious? I rarely drink spirits and occasionally substitute beer for wine. I play football and squash. I walk 3 kilometres to and from work. I lead a normal life and, probably due to regular consumption, I never feel drunk, but presumably I am considered a binge drinker. I don’t want advice from a government minister or associated medic. I want objective information. Am I lucky? Or is my consumption relatively harmless? What’s the truth?

David Hunte

London, UK

A UK unit is 10 millilitres (8 grams) of alcohol - Ed.

The questioner may not be getting away with his alcohol consumption as lightly as he thinks. The liver has a remarkable ability to carry on working, and liver function tests may remain normal even when the organ is quite badly damaged. The gamma GT test is more sensitive than other enzyme tests at detecting damage, but it is often not offered to National Health Service patients in the UK because of its cost.

I also think the writer has underestimated his consumption. If he really drinks a bottle of wine a day then, given the strength of typical popular wines, I would estimate that he could be drinking more than 60 units a week. In more than 30 years of general practice almost everyone I encountered drinking more than 40 units a week was damaging his or her health in some way, through addiction, hypertension, liver or gastric problems, or mental problems.

That said, government advice on alcohol consumption is necessarily arbitrary, and there is great genetic variation in the way that people metabolise and tolerate alcohol.

Anthony Daniel

General Practitioner

Sevenoaks, Kent, UK

The short answer is that, like a 90-year-old smoker, you are just lucky. The government limits of 2 or 3 units per day for women and 3 or 4 units per day for men are based on epidemiological evidence. The complex mix of factors influencing our health makes it impossible to issue cast-iron predictions of what will happen to a particular individual at a given level of consumption.

One bottle of wine typically contains 10 UK units or about 80 grams of alcohol. Drinking a bottle a day has been shown to increase the risk of liver cirrhosis 18-fold. You are also five times as likely to get cancer of the oral cavity, and two to three times as likely to get laryngeal or oesophageal cancer, to have a stroke, or to suffer from essential hypertension or chronic pancreatitis.

These are relative risks. What they are relative to will depend on a number of factors, including genetics. The liver is vulnerable to excess fat, so an active lifestyle and low-fat diet will reduce the risk of liver disease.

Rachel Seabrook

Institute of Alcohol Studies

St Ives, Cambridgeshire, UK