IELTS Academic Reading Practice Test 504

The Tasmanian devil is a stocky, black-furred marsupial roughly the size of a small dog. It is the largest living carnivorous marsupial. An adult male measures about 60 centimetres from nose to tail base and usually weighs between six and eight kilograms, while the female is noticeably smaller. In the wild the species lives only on Tasmania, the island state south of the Australian mainland, where it occupies dry forest, woodland and coastal scrub. Both sexes carry the same markings: a white band across the chest, a scattering of pale patches, and ears that flush red when the animal is excited.

The common name was given by European settlers, who heard its extraordinary nocturnal cries and concluded that something diabolical was abroad in the bush. In fact the devil is a solitary animal that spends the day resting in a hollow log, a burrow or a dense thicket, and emerges at night to search for food. It is not a fast runner and does not pursue prey over long distances. The largest carnivorous marsupial of modern times, the thylacine, died out in the 1930s, and ever since the devil has been the biggest predator left on the island.

Devils are best understood as specialised eaters of carrion. Most of their food comes from animals that are already dead: wallabies, wombats, possums, sheep and, on the coast, seals and seabirds. A single carcass may attract a dozen animals at once, all screaming and lunging at one another in a display that looks more violent than it usually is.

Their jaws are disproportionately large, and a study measuring bite force in relation to body mass reported that the devil's is the strongest of any living mammal. Powerful muscles and heavy teeth allow the animal to crush bone, and devils typically consume the whole carcass, hide and fur included, leaving little behind.

Females mate in March. After a gestation of about three weeks they give birth to as many as thirty young, each no larger than a grain of rice. Only four can be reared, because the pouch contains just four teats. The survivors stay attached for roughly four months, then ride on their mother's back for several weeks before becoming independent at around eight months. In the wild a devil rarely lives longer than five or six years.

In 1996 a wildlife photographer working in the north-east of Tasmania noticed a devil with strange growths on its face. The growths proved to be a cancer that passes from one animal to another when they bite each other about the mouth, as devils do constantly while feeding. Named devil facial tumour disease, it is one of only a handful of transmissible cancers known in nature. Affected animals develop large lesions that interfere with eating, and they usually die of starvation or organ failure within a few months. In some regions the disease has been followed by declines of more than 80 per cent.

The response has been extensive. In 2008 the species was formally listed as endangered. A national programme was then set up to manage the wild population and to maintain a captive insurance population in zoos and mainland sanctuaries. These animals are kept apart from one another in quarantine conditions so that the cancer cannot spread. In 2012 and 2013 healthy devils were moved to Maria Island, off Tasmania's east coast, as a further safeguard. Such programmes are expensive and cannot protect the wild population directly, but they reduce the risk that a single outbreak will wipe out the species.

Genetics complicates the picture. Devils have unusually low genetic diversity, which is thought to have left them less able to resist the tumour. It also limits the choice of animals for breeding programmes, since pairs that are too closely related produce weak offspring. Yet there are signs of hope. In several long-studied populations the proportion of animals with tumours has fallen, and researchers have found tentative evidence that some devils are developing tolerance of the disease. A second cancer, known as devil facial tumour 2, was identified in 2014 and appears to spread in the same way, though it is less common.

Devils once lived on the Australian mainland as well, and bones from caves and rock shelters show that they disappeared from it roughly 3,000 years ago. That was long before Europeans arrived. The reasons are debated. Competition with the dingo, which reached the continent a few thousand years earlier, is one explanation; climate change and changing land use are others. In 2020 a conservation organisation released the first devils into a large fenced sanctuary in the Barrington Tops region of New South Wales. The long-term aim is a population that can survive without fences.

Today the devil's main causes of death, apart from the facial tumour, are collisions with vehicles and, for young animals, the attentions of eagles and older devils. Its image is among the most recognisable in Australia and is used by the state's tourism industry and by conservation campaigns. For a species with such a fearsome reputation, the devil turns out to be remarkably vulnerable: a scavenger that cannot run fast, that has a small range and that depends on a limited area of suitable habitat.

Most of the world's sign languages have histories stretching back centuries, and like spoken languages they are passed from one generation to the next. Occasionally, however, a completely new sign language appears within a few generations, and linguists have come to regard these rare cases as a natural experiment. A language that is being created in front of observers offers something the study of older languages cannot: a record of how grammar begins. Several such languages have been documented, in Israel, Indonesia, Nicaragua and the United States, and comparing them has started to answer long-standing questions about the origins of language.

Two conditions seem to be necessary. The first is a community in which deafness is unusually common. In small, relatively isolated villages where marriages between relatives occur, a recessive gene for deafness can become frequent, so that a noticeable proportion of children are born deaf. The second is a group of deaf children large enough to form a community of their own. Where both conditions are met, signing emerges quickly; where deafness is common but deaf people remain scattered, it may not.

Before the 1970s deaf Nicaraguans had little contact with one another. The country had no school for deaf children, and most used improvised gestures with their families. In 1977 a school was opened in Managua, and a vocational school followed in 1980. Children who arrived with their own individual systems of gesture began to communicate with each other. Within a few years a shared vocabulary had appeared. The psychologist Ann Senghas, who has studied the community for decades, compared children who joined the school at different times. She found that those who began to sign at a younger age used more consistent and more elaborate grammar than those who learned later.

The Al-Sayyid Bedouin, a community in the Negev desert, offer an older example. Deafness is common there because of a recessive gene, and a sign language has developed over three or four generations, used by deaf and hearing villagers alike. The linguist Wendy Sandler and her colleagues found that word order had settled very early. Signers consistently place the object before the verb, although the surrounding spoken language, Arabic, does not. Other grammatical machinery, such as a system for marking the relations between clauses, took considerably longer to appear.

Kata Kolok, used in a village in northern Bali, has been studied by Connie de Vos. Its deaf users are integrated into village life, and many hearing people learn it too. It is notable for the way it handles space. Rather than describing positions relative to the signer's body, as most sign languages do, signers use fixed directions such as uphill and downhill, or north and south, wherever they are standing.

Earlier still is the language of Martha's Vineyard, an island off the coast of Massachusetts where hereditary deafness was common in the nineteenth century. Because so many islanders were deaf, almost everyone in some towns could sign. Accounts from the island describe hearing and deaf residents conversing without difficulty. The language is thought to have contributed to American Sign Language when island children were sent to the American School for the Deaf, founded in 1817 in Hartford, Connecticut.

Why should some communities produce a full language while others do not? The answer appears to lie in the number and the ages of the learners. A single deaf child, however intelligent, will invent only a limited personal system, sometimes called home sign; such systems have structure but no fixed grammar, and each child's is different. Where children can learn from slightly older children, by contrast, each generation inherits the achievements of the last and adds to them. Communities in which hearing people also sign give deaf children many more people to learn from. It is this chain of transmission, rather than any quality of the individual, that turns gesture into a language.

Not every case fits so neatly. On Providence Island, a small Colombian island in the Caribbean with a sizeable deaf population, the local sign language has been described by researchers as limited. Its signs are heavily dependent on the situation in which they are used. Sign systems elsewhere, in parts of Mexico and Thailand, have likewise appeared without developing the elaborate grammar found in Nicaragua or the Negev. The influence of the surrounding spoken language is another uncertainty. Some researchers argue that it is slight, while others believe that the patterns of a spoken language gradually shape the sign language alongside it.

These languages are also disappearing. In Nicaragua and in the Balinese village, deaf children are increasingly sent to mainstream schools or leave for the cities, so the young learners on whom the system depends are no longer present. Linguists are therefore recording them while they can. The study of how a new sign language forms is unlikely to be repeated once its communities have dispersed, and every such language documented adds to our understanding of the human capacity for language. What is lost is not only a set of signs but a record of what human beings do when they have to invent a language from nothing.

Thirty kilometres an hour is about the speed of a brisk cyclist. For most of the twentieth century it would have seemed an absurdly low limit for a city street. That has changed. Brussels made 30 km/h the default across almost the whole of its region at the start of 2021, Paris followed later the same year, and Spain adopted the same limit on most urban streets. Wales went further in September 2023, replacing 30 mph with 20 mph, roughly 32 km/h, on the roads where people live. The question is no longer whether such limits are feasible but whether they deliver what their supporters promise.

The argument from physics is the simplest and the strongest. The energy a moving vehicle carries rises with the square of its speed. A car travelling at 50 km/h therefore holds nearly three times as much energy as the same car at 30 km/h. Almost all of it has to be absorbed by whatever the car hits. Stopping distances grow in a similar way, and the distance covered while the driver reacts adds a further fixed amount. The consequences for a pedestrian are severe: the chance of surviving a collision falls steeply somewhere between 30 and 50 km/h. The physics, at least, is settled.

The evidence about limits themselves is messier. Evaluations of 20 mph schemes in London and Bristol have generally reported fewer collisions and fewer serious injuries, but the size of the reduction varies widely from one study to another, and some schemes show little effect at all. One difficulty is that limits are rarely introduced alone. A council that lowers a limit usually adds signs, markings and perhaps a raised crossing at the same time, so the effect of the limit as such cannot be separated out. Another is that collisions are, fortunately, rare events, so changes in their number are hard to distinguish from ordinary fluctuation.

Then there is the question of obedience. A painted figure on a circular sign changes nothing by itself, and studies of new limits commonly find that average speeds fall by only a fraction of the intended amount in the first months. Speeds drop most where the street itself has been rebuilt to suggest that it is not a through route: narrowed at junctions, planted with trees, given a surface that looks like a shared space. There is also a counter-argument, advanced by a minority of researchers, that a road which feels unusually safe may encourage drivers to pay less attention. Pedestrians, too, may take more chances. The evidence for such risk compensation in urban driving is thin, but it is not nonexistent.

The costs are real and easy to count. New signs, road markings and, where they are installed, physical measures such as speed tables must be paid for. So must the enforcement that makes any of them credible. Lower limits also lengthen journeys slightly, and the time lost is borne by drivers, delivery firms and bus operators. The benefits, by contrast, are spread thinly across everyone who lives on or walks along the street. That asymmetry helps to explain why the argument is often heated: the losses are concentrated and immediate, while the gains are diffuse and delayed.

Environmental claims are more uncertain than they look. Tyre noise falls as speeds drop, so quieter streets are a plausible benefit where traffic flows freely. Emissions are another matter. Modern engines run most efficiently at moderate speeds, and in stop-start traffic a car may burn more fuel per kilometre than it would at 50 km/h. Whether a city-wide limit raises or lowers total emissions therefore depends on the traffic, the vehicles and the enforcement. Modelling studies have reached different conclusions, and anyone who claims the answer is obvious is overstating what is known.

The strongest case, in my view, has less to do with the severity of collisions than with the kind of city a street allows. Traffic at 50 km/h needs wide lanes, generous sight lines and space between junctions; at 30 km/h the same road can be narrower, easier to cross, and can carry trees, benches and cycle parking. Streets designed on those lines produce more walking and more cycling, and the health gains from everyday activity are well documented. They also produce more customers for the shops along them, since people on foot stop more often than people in cars. The benefits of a lower limit extend well beyond the injuries that are prevented.

So should every city street be limited to 30 km/h? Not quite. A busy arterial road with no homes on it, carrying buses and freight across a city, is a different proposition from a residential street where children walk to school. My own view is that 30 km/h should be the default wherever people live, shop or learn, and that higher limits should be the exception, justified street by street. Above all, a limit must be credible. A sign that nobody obeys is worse than no sign at all, because it teaches drivers to disregard the next one as well.