IELTS Academic Reading Practice Test 104

Chewing gum is such an ordinary product that it is easy to forget how long people have chewed materials for pleasure. Lumps of birch bark tar bearing the marks of human teeth have been recovered from prehistoric sites in northern Europe, so the habit of chewing without swallowing is ancient. The modern industry, however, has a surprisingly specific origin, in the meeting of an exiled general, a New York inventor and a tree from the forests of Central America.

In Central America the Maya chewed chicle, the milky latex of the sapodilla tree. Men known as chicleros climbed the trees and cut zigzag wounds in the bark, so that the latex ran down into a container tied beneath. The gum was dried, cut into blocks and chewed to clean the teeth, to freshen the breath and to suppress hunger on long journeys. Spanish officials recorded the practice with disgust in the sixteenth century, but chicle remained a local material for another three hundred years.

In the north-east of what is now the United States, a different material served the same purpose. The indigenous peoples of New England chewed the resin of spruce trees, and European settlers adopted the habit. The resin was collected from wounds in the bark, where it dried in brittle amber lumps; chewing softened it, and sellers added mint, liquorice or beeswax to improve the texture. By the 1840s entrepreneurs were selling it commercially, and a firm in Maine wrapped blocks in tissue paper and sold them through pharmacies. Spruce gum was a modest business, but it established the idea of gum as a product.

Chicle reached New York through Antonio López de Santa Anna, the former president of Mexico, who was living in exile on Staten Island in the late 1860s. Rubber was then in enormous demand for tyres, hoses and waterproof cloth, and Santa Anna believed that chicle might serve as a cheap substitute. He brought a supply to Thomas Adams, an inventor and photographer, who spent months trying to harden the gum so that it could be moulded. Adams made shoes, carriage wheels and toys, but every attempt failed: chicle was too soft and slowly lost its shape.

Adams then noticed that his visitor chewed the raw chicle while they talked. He boiled a batch, rolled it into long strips and sold them from a drugstore. In 1871 he introduced Adams' New York Gum, at first unflavoured and later flavoured with liquorice. It sold well. In 1888 his company installed the first vending machines on the elevated railway stations of New York, offering a fruit-flavoured gum, and rival manufacturers quickly appeared.

William Wrigley Jr. arrived in Chicago from Philadelphia in 1891 with a talent for selling. His business was soap, and he offered free baking powder as a premium to shopkeepers who stocked it. When the baking powder proved more popular than the soap, he offered chewing gum as the premium instead, and the gum outsold both. He began manufacturing his own, launching Spearmint and Juicy Fruit in 1893 and Doublemint in 1914. Wrigley's success rested less on the recipe than on advertising: he spent a large share of his income on newspaper pages, painted signs and electric billboards.

Free samples did much of the rest. Wrigley mailed gum to households listed in telephone directories and gave it away at fairs and sports grounds. During the two world wars the company supplied the armed forces, and gum was included in the rations issued to troops. For many young soldiers it was the first gum they had tasted. The habit travelled home with them and to the places where they were stationed, opening export markets that the company later supplied directly. By the 1930s Wrigley was one of the largest advertisers in the United States.

Chicle had one serious weakness: it came from wild trees. Tapping was seasonal, the trees grew slowly, and the supply depended on a workforce that cut its way deeper into the forest each year. When shipping was disrupted during the Second World War, chemists accelerated work that had begun in the 1920s on synthetic bases. By the 1950s polymers such as polyvinyl acetate, together with resins, waxes and fillers, had largely replaced chicle. A synthetic base could be manufactured to a specification, cost less and was consistent from batch to batch. Demand for chicle collapsed, and the chicleros' trade now survives only on a small scale.

Chewing gum might have remained a quiet adult habit had it not been for bubble gum. In 1928 Walter Diemer, an accountant at the Fleer company, was experimenting with a formula that would stretch without sticking to the face. The batch he produced was pink, because that was the colouring to hand, and it was marketed as Dubble Bubble. Bubble gum became a children's product, and the pink colour became standard.

Today gum is sold in enormous quantities, and its disadvantages are equally familiar. Because the base is synthetic, it does not decay, and removing it from pavements is expensive. Some manufacturers now collect waste gum and recycle it into compounds used in shoe soles and other products. Dentists, meanwhile, point out that sugar-free gum sweetened with xylitol stimulates saliva and helps to neutralise the acids that cause decay. Singapore went further in 1992 and banned the sale of chewing gum, a restriction since partly relaxed.

The giraffe is the tallest living land animal, with males reaching more than five metres, and its neck is the most striking feature of its anatomy. Yet the neck contains only seven cervical vertebrae, the same number as a mouse or a human being; each vertebra is simply enormously elongated. Explaining how such a structure evolved has occupied biologists for more than two centuries, and the argument is still not settled. The debate matters beyond the giraffe itself, because it exposes how difficult it is to reconstruct the pressures that shaped a trait millions of years ago.

The first systematic attempt came from Jean-Baptiste Lamarck in 1809. Lamarck argued that organisms change during their lives in response to their needs, and that a trait acquired in this way can be passed on to offspring. A giraffe that stretched upwards to reach the highest foliage, he suggested, would develop a slightly longer neck, and its descendants would inherit the improvement and stretch further still. The account was elegant, and it made the giraffe a favourite illustration in nineteenth-century textbooks, but modern genetics provides no mechanism by which such changes could be inherited.

Charles Darwin offered a different mechanism. In any population, he observed, individuals vary, and those whose necks allow them to reach foliage that others cannot reach will survive when food is scarce and leave more offspring. Over many generations the average neck becomes longer. This is the competing-browsers hypothesis: a giraffe can feed above the reach of antelopes and other browsers, and above the thorny lower branches of the acacia trees on which it depends. Acacia leaves are nutritious but defended by thorns, so a browser that feeds above them gains food that smaller animals cannot reach. Darwin discussed the giraffe in later editions of On the Origin of Species, and later writers developed the argument in detail. The idea is intuitive, and it remains the explanation found in most school textbooks.

In 1996 two zoologists, Robert Simmons and Lue Scheepers, questioned it. They pointed out that giraffes often browse at shoulder height, and that during the dry season they eat low shrubs; both sexes reach the same high leaves, so a long neck brings no obvious advantage to a female. They proposed instead that the necks were shaped mainly by sexual selection. Males use their necks as weapons, swinging their heads at rivals, and a longer, heavier neck is an advantage in those contests.

The anatomical evidence is suggestive. Adult males have proportionately longer and much thicker necks than females, and the difference grows with age, because bone is deposited on the skull and vertebrae as an animal matures. Males fight frequently, and observers report that success in these contests correlates with neck size. Females, by contrast, stop growing earlier and rarely fight. Feeding cannot easily explain why the two sexes should differ so markedly, since both eat from the same trees.

Fossils have recently added a further twist. In 2022 a team described Discokeryx xiezhi, a relative of the giraffe from the early Miocene of Xinjiang, China, roughly seventeen million years old. Its neck was short, but its skull carried a thick, disc-shaped mass of bone, and the joints between the skull and the spine appear built to absorb heavy impacts. The authors interpreted these features as adaptations for head-butting, which suggests that combat among males evolved before the neck began to lengthen. Another fossil, Samotherium, from the Miocene of the eastern Mediterranean, has a neck intermediate in length between that of a giraffe and that of the okapi, its closest living relative, and shows that elongation proceeded gradually.

A long neck also creates an engineering problem. To push blood to a brain more than two metres above the heart, the giraffe must generate a blood pressure roughly twice that of a human being, and its heart may weigh eleven kilograms. When the animal lowers its head to drink, gravity would drive blood into the skull; a network of small vessels at the base of the brain cushions the pressure, and valves in the jugular veins slow the return of blood to the chest. The skin on the lower legs is tightly stretched, which helps to stop blood pooling there. Drinking is also the moment when a giraffe is most vulnerable, because it must spread its forelegs and lower its head to the water.

Neither hypothesis is likely to be wholly right. A long neck may serve several purposes at once, and the balance of advantage may differ between males and females or between seasons. What is clear is that the neck is not a simple solution to a single problem; it is a compromise between feeding, fighting and the demands of circulation. Males and females may have been shaped by somewhat different pressures acting on the same structure. The debate also shows how easily a plausible story can harden into accepted fact, and that the most obvious explanation is not always the best supported.

Every generation of adults has worried about the influence of new media on the young. In the nineteenth century there were complaints that cheap novels were corrupting impressionable readers; in the twentieth, television was blamed for weakening family life and shortening attention spans. The current concern is social media, and the debate around it is unusually polarised. Some commentators present smartphones as the cause of a crisis in adolescent mental health, while others dismiss the alarm as a moral panic. Neither position, in my view, is supported by the evidence. The result is a conversation in which evidence is often selected to support a position already held.

There is no doubt that the technology now occupies a central place in many teenagers' lives. Surveys in Britain, the United States and other wealthy countries commonly find that most adolescents use at least one social platform every day, and a substantial minority report using it for several hours. Most platforms set a minimum age of thirteen, but younger children often join anyway, sometimes with their parents' knowledge. The numbers alone, however, tell us little about effects. A teenager who spends two hours messaging close friends is doing something very different from one who spends the same time scrolling through images of strangers.

The most careful work on the subject has been done by psychologists using large datasets that follow thousands of young people over time. In 2019 Amy Orben and Andrew Przybylski, then at Oxford, published an analysis of three such datasets in the journal Nature Human Behaviour. They found a small negative association between social media use and life satisfaction, but the effect was tiny: it was similar in size to the association between well-being and eating potatoes, or between well-being and wearing glasses. The authors also used a technique that tested thousands of different ways of analysing the data, and found that the results varied widely depending on the choices made. Their conclusion was that the effect of social media on adolescent well-being is, on average, very small.

Other researchers interpret the same period very differently. The American psychologist Jean Twenge has argued that the rise in reports of anxiety and depression among adolescents began at roughly the same time as smartphones became widespread, and that the timing is too close to be coincidence. In his 2024 book The Anxious Generation, the social psychologist Jonathan Haidt goes further, blaming a 'phone-based childhood' for a range of problems. Such arguments have persuaded many parents and some governments. Yet the timing is not consistent across countries: in some places where smartphone use rose just as quickly, rates of adolescent distress did not follow the same path. Timing alone cannot establish cause.

One difficulty is that 'social media use' is a crude category. A platform on which users compare their bodies with edited photographs is not the same as a group chat in which friends arrange to meet. Several mechanisms are plausible. Sleep may be displaced by late-night scrolling, and lost sleep is known to affect mood. Notifications interrupt concentration, and the design of many apps encourages constant checking. Social comparison and online bullying are real sources of distress for some young people. But these mechanisms are likely to affect particular individuals in particular circumstances, not whole populations in a uniform way. The same amount of time spent passively viewing strangers' lives may be more harmful than active conversation.

It is equally important to recognise what social media can provide. For teenagers who feel isolated because of their sexuality, a disability or a minority identity, online communities can offer support that is unavailable locally. Creative platforms allow young people to share music, writing and art with an audience far beyond their school. Some mental health services now reach adolescents through the channels they already use. Research suggests that the benefits and the harms are unevenly distributed: the same technology that intensifies comparison for one teenager may provide a lifeline for another.

Governments have begun to respond. In late 2024 Australia passed a law that will bar children under sixteen from using social media, with platforms expected to take reasonable steps to verify age. The intention is understandable, and the measure is popular with many parents. I doubt, however, that a ban will achieve what its supporters hope. Determined teenagers can find ways around age checks, and a rule that removes support networks from vulnerable young people may do more harm than good. It also lets the companies that design addictive features escape responsibility. A more promising approach is to regulate those features directly, as governments already regulate gambling and tobacco advertising.

None of this means that parents should ignore the subject. The evidence supports limits around sleep, meals and homework, and it supports conversations about what young people see online. Schools can teach pupils the digital skills to recognise manipulated images and to think critically about the content that algorithms place in front of them. But the larger responsibility lies with the companies that profit from attention. If the average effect of social media on teenagers is small, that is partly because small effects, repeated across millions of people, can still shape a generation. The question is not whether screens are good or bad, but who controls them and to what purpose. That is a question about design and business models, not merely about the amount of time a teenager spends on a phone.