The Body: A Guide for Occupants

"The back of your head is a modest ligament, not found on other apes, that instantly betrays what it is about us that allowed us to thrive as a species. It is the nuchal ligament and it has just one job: to hold the head steady when running. And running – serious, dogged, long-distance running – is the one thing we do superlatively well. We are not the speediest of creatures, as anyone who has ever chased a dog or cat or even an escaped hamster will know. The very fastest humans can run about 20 miles an hour, though only for short bursts. But put us up against an antelope or wildebeest on a hot day and allow us to trot after it, and we can run it into the ground. We perspire to keep cool, but quadrupedal mammals lose heat by respiration – by panting. If they can't stop to collect themselves, they overheat and become helpless. Most large animals can't run for more than about 15 kilometres before they drop. That our ancestors could also organize themselves into hunting parties, to harry quarry from different sides or drive prey into confined spaces, made us all the more effective.

Fossil evidence suggests that early hominins were walking by about six million years ago, but needed an additional four million years to acquire the capabilities for endurance running and, with it, persistence hunting.

Unlike the rest of the body, the palms don't sweat in response to physical exertion or heat, but only from stress. Emotional sweating is what is measured in lie-detector tests.

Before penicillin, the closest thing to a wonder drug that existed was Salvarsan, but it was effective against only a few things, principally syphilis, and had a lot of drawbacks. For a start, it was made from arsenic, so was toxic, and treatment consisted of injecting roughly a pint of solution into the patient's arm once a week for 50 weeks or more.

The (current) rate of antibiotic withdrawals – because they don't work any more or have become obsolete – is twice the rate of new introductions. The obvious consequence of this is that the arsenal of drugs we have to treat bacterial infections has been going down and there is no sign of it stopping. What makes this much worse is that a great deal of our antibiotic use is simply crazy. Almost three-quarters of the forty million antibiotic prescriptions written each year in the United States are for conditions that cannot be cured with antibiotics..... Even more appallingly, in the United States 80 per cent of antibiotics are fed to farm animals, mostly to fatten them. Fruit growers can also use antibiotics to combat bacterial infections in their crops. In consequence, most Americans consume second-hand antibiotics in their food ... without knowing it.

On some diseases penicillin now has no effect at all. In consequence, the death rate from infectious diseases has been climbing and is back to the level of about forty years ago...... As a doctor put it to me: ‘We are looking at a possibility where we can't do hip replacements or other routine procedures because the risk of infection is too high.’ The day when people die once again from the scratch of a rose thorn may not be far away.

Antibiotics are about as nuanced as a hand grenade. They wipe out good microbes as well as bad. Increasing evidence shows that some of the good ones may never recover, to our permanent cost. Most people in the Western world, by the time they reach adulthood, have received between five and twenty courses of antibiotics. The effects, it is feared, may be cumulative, with each generation passing on fewer microorganisms than the one before.

Producing new drugs is expensive. All but two of the eighteen largest pharmaceutical companies in the world have given up the search for new antibiotics. People take antibiotics for only a week or two. Much better to focus on drugs like statins or antidepressants that people can take more or less indefinitely.

Funk didn't discover vitamins but merely speculated, correctly, as to their existence. But since no one could produce these strange elements, many authorities refused to accept their reality. Sir James Barr, president of the British Medical Association, dismissed them as ‘a figment of the imagination’

There is disagreement over what precisely we do need. In America, the daily recommended dose of vitamin E is 15 milligrams, but in the UK it is 3 to 4 milligrams – a very considerable difference.

Even today vitamins are an ill-defined entity. The term describes 13 chemical oddments that we need to function smoothly but are unable to manufacture for ourselves. Though we tend to think of them as closely related, they mostly have little in common apart from being useful to us.

Smell is said to account for at least 70 per cent of flavour and maybe even as much as 90 per cent.

"When you eat, most of the aroma reaches you not through your nostrils but by the back staircase of your nasal passage, what is known as the retronasal route – as opposed to the orthonasal route up your nose.

Many tests have been done to demonstrate how easily we are fooled with respect to flavour. In a blind taste test at the University of Bordeaux students in the Faculty of Oenology were given two glasses of wine, one red and one white. The wines were actually identical except that one had been made a rich red with an odourless and flavourless additive. The students without exception listed entirely different qualities for the two wines. That wasn't because they were inexperienced or naive. It was because their sight led them to have entirely different expectations, and this powerfully influenced what they sensed when they took a sip from either glass. In exactly the same way, if an orange-flavoured drink is coloured red, you cannot help but taste it as cherry.

The appendix, has no certain purpose but kills about 80,000 people around the world every year when it ruptures or grows infected..... Now the best thinking is that the appendix serves as a reservoir for gut bacteria.

It isn't just a big brain that allows us to speak, but an exquisite arrangement of anatomy. One reason chimpanzees can't talk is that they appear to lack the ability to make subtle shapes with tongue and lips to form complex sounds.

The bottom line is that we ended up with brains big enough to handle complex thoughts and vocal tracts uniquely able to articulate them."

Stuttering affects 1 per cent of adults and 4 per cent of children. For reasons unknown, 80 per cent of sufferers are male. It is more common among left-handers than right-handers, especially those who have been made to write right-handed.

For many, the stammering miraculously ceases when they sing their words, speak in a foreign language or talk to themselves. The majority of speakers recover from the condition by their teenage years and females seem to recover more easily than men .

Most other mammals never suffer strokes, and for those that do it is a rare event. But for humans, it is the second most common cause of death globally, according to the World Health Organization. Why this should be is something of a mystery.

The 18th & 19th centuries were very bad....medicine sank into a kind of dark age. You could hardly imagine more misguided and counterproductive practices than those to which physicians became attached in the eighteenth century, and even much of the nineteenth.

Bleeding people was one of those aberrations. It may seem to us self-evidently foolhardy to bleed and pummel a person who is already severely ill, but such practices lasted an extraordinarily long time. Bleeding was thought to be beneficial not just for illness, but to instil calm. Frederick the Great of Germany was bled before battle just to soothe his jangled nerves. Bleeding bowls were treasured within families and passed on as heirlooms.... Why did bleeding persist for so long? The answer is that until well into the nineteenth century most doctors approached diseases not as distinct afflictions, each requiring its own treatment, but as generalized imbalances affecting the whole body. They didn't give one drug for headaches and another for, say, ringing in the ears, but rather endeavoured to bring the whole body back into a state of equilibrium by purging it of toxins through the administration of cathartics, emetics and diuretics, or by relieving the victim of a bowl or two of blood. George Washington was probably killed this way by his doctors.

Altogether humans are afflicted by some fifty types of autoimmune disease, and the numbers are rising. Take Crohn's disease... When it was recognised in 1932 it affected on person in 50,000..... Then it became one in 10,000, then one in 5,000. Today the proportion is one in 250 and still rising. Why this has happened no one can say. Daniel Lieberman suggests that the overuse of antibiotics and the consequent depletion of our microbial reserves may have made us more susceptible to all autoimmune diseases, but acknowledges that the 'causes remain elusive'.

Equally bewildering is that autoimmune diseases are grossly sexist..... Altogether, 80 per cent of all autoimmune diseases occur in women. Hormones are the presumed culprit but how exactly female hormones trip up the immune system when male hormones don't is not at all clear.

A person who smokes cigarettes regularly (about a pack a day) is fifty times more likely than a non-smoker to get cancer.... Yet it took for ever to gain consensus that smoking caused lung cancer. It seems crazy to us today but it wasn't so crazy to people back then. The problem was that a huge proportion of people smoked – 80 per cent of all men by the late 1940s – yet only some of them developed lung cancer. And some people who didn't smoke also developed lung cancer. So it was not especially straightforward to see a direct link between smoking and cancer. When lots of people are doing something and only some of them are dying from it, it makes it hard to impute blame to a single cause.

Things have changed. Today just 18 per cent of Americans smoke and it is easy to think that we have pretty much solved the problem. But it's not quite as simple as that. Nearly one-third of people below the poverty line still smoke, and the habit continues to account for one-fifth of all deaths. It is a problem we are a long way from rectifying.

"According to one study, the number of bacteria on you actually rises after a bath or shower because they are flushed out from nooks and crannies.

The problem with antibacterial soaps is that they kill good bacteria on your skin as well as bad. The same is true of hand sanitizers