Reading Test 5

You should spend about 20 minutes on Questions 1–13, which are based on Reading Passage 1 below.

The Great Stink

How a hot summer changed London for ever

In the summer of 1858, London experienced a crisis that came to be known as the Great Stink. For decades, the city's waste had been flowing into the River Thames, and as the population grew to more than two and a half million, the river had become little more than an open sewer. That June, a long spell of unusually hot weather caused the level of the river to fall and the waste along its banks to decay in the sun. The smell was so overpowering that the curtains of the Houses of Parliament, which stand beside the river, were soaked in chemicals in an attempt to block it out, and politicians considered moving their work to another town.

The problem had been growing for many years. Ironically, part of the cause was an improvement in sanitation. The flushing toilet had become increasingly popular among wealthier households, and since the 1840s, regulations had required houses to be connected to the sewers rather than to cesspits. The sewers, however, had been designed to carry rainwater, and they emptied directly into the Thames. At the same time, several water companies continued to take drinking water from the same river.

The consequences were deadly. London suffered serious outbreaks of cholera in 1832, 1849 and 1854, which together killed tens of thousands of people. At the time, most doctors believed that cholera was spread by a 'miasma', or bad air, rising from decaying matter. In 1854, a doctor named John Snow challenged this view. By plotting the homes of victims of an outbreak in Soho on a map, he showed that most of them had drawn water from a single public pump in Broad Street. When the handle of the pump was removed at his request, the outbreak, which was already declining, came to an end. Snow's theory that the disease was carried in water was not widely accepted for many years, however.

Ironically, it was the miasma theory, rather than Snow's evidence, that finally persuaded parliament to act. If bad smells caused disease, then the Great Stink represented an immediate danger to everyone in the city, including the politicians themselves. Within weeks, parliament had passed a law giving the Metropolitan Board of Works the power and the money to build a new system of sewers. The task was given to the board's chief engineer, Joseph Bazalgette, who had already drawn up plans.

Bazalgette's solution was to build a network of large sewers running parallel to the river, which would intercept the waste before it reached the Thames and carry it east, to points downstream of the city where it could be released into the river on the outgoing tide. Some 132 kilometres of these main sewers were constructed, connected to around 1,800 kilometres of smaller street sewers. Because much of London is low-lying, the waste could not always flow by gravity alone, and four large pumping stations were built to lift it. The most famous, at Crossness and Abbey Mills, were designed in a highly decorative style, with elaborate ironwork that has led them to be described as cathedrals of sewage.

One of Bazalgette's most important decisions concerned the size of the pipes. Having calculated the diameter required for the existing population, he reportedly said, 'We're only going to do this once,' and doubled it. This decision allowed the system to cope with the city's enormous growth over the following century. Part of the network was also built inside new embankments along the river, which reclaimed land from the Thames and provided space for roads and, later, an underground railway.

The results were dramatic. When cholera returned to London in 1866, it struck mainly in an area of east London that had not yet been connected to the new system, a fact that did much to persuade doctors that Snow had been right. After that, the city never again suffered a major outbreak. Much of Bazalgette's network remains in use today, but it has finally reached its limits. Because the sewers also carry rainwater, heavy storms regularly cause them to overflow into the Thames. To solve this problem, a new 25-kilometre tunnel, sometimes called the 'super sewer', has been built beneath the river, and was completed in 2025.

You should spend about 20 minutes on Questions 14–26, which are based on Reading Passage 2 below.

Cooling the city

On a still summer evening, the centre of a large city can be several degrees warmer than the surrounding countryside. This phenomenon, known as the urban heat island effect, has been recognised since the early nineteenth century, when the amateur scientist Luke Howard recorded that temperatures in London were consistently higher than those in nearby rural areas. Today, with more than half of the world's population living in cities and global temperatures rising, it has become a serious concern for urban planners.

Several factors combine to produce the effect. Dark surfaces such as asphalt roads and roofs absorb a large proportion of the sun's energy during the day and release it slowly as heat after sunset, which is why the difference between city and countryside is usually greatest at night. Tall buildings close together create what are known as urban canyons, which trap heat and reduce the movement of air. Cities also have far less vegetation than rural areas. Plants cool their surroundings by releasing water vapour through their leaves, a process called evapotranspiration, and they provide shade. Finally, cities generate heat of their own, from vehicles, industry and air-conditioning units, which pump heat out of buildings and into the streets.

The consequences can be severe. Heatwaves are among the deadliest forms of extreme weather, and their effects are concentrated in cities. During the European heatwave of 2003, around 70,000 more people died than would normally have been expected, many of them elderly people living alone in city apartments. High night-time temperatures are particularly dangerous, because they deprive the body of the chance to recover from the heat of the day. Higher temperatures also increase the demand for air conditioning, which raises energy consumption and, by releasing more heat, makes the problem worse.

Cities around the world are now experimenting with ways of keeping cool. One of the simplest is to change the colour of surfaces. Roofs painted white or covered with reflective materials, often called cool roofs, can be many degrees cooler than dark ones on a sunny day, reducing the heat that enters the building below. In 2017, Los Angeles began coating some of its streets with a light-grey reflective material, and early measurements suggested that the treated surfaces were noticeably cooler than ordinary asphalt. Critics have pointed out, however, that reflected heat may make pedestrians feel hotter, as some of the energy bounces back towards them.

Planting trees and creating green spaces is another widely used approach. In Medellín, Colombia, the city authorities created a network of more than thirty 'green corridors', planting trees and shrubs along roads and streams. Officials reported that temperatures along the corridors fell by around two degrees. Paris has taken a different approach, transforming school playgrounds, which were traditionally covered in asphalt, into green 'oases' with trees, plants and surfaces that absorb water. Outside school hours, some of these playgrounds are opened to local residents, providing cool places for people to go during heatwaves.

Green spaces have limitations, however. Trees take many years to reach their full size, they need water, which may be scarce during the hottest periods, and space for planting is limited in dense city centres. For this reason, some cities are also focusing on the design of buildings and streets. Traditional architecture in hot countries often provides useful lessons: narrow streets that are shaded for much of the day, thick walls that absorb heat slowly, and courtyards and fountains that cool the air. Modern planners are increasingly rediscovering these ideas.

No single measure can solve the problem, and experts agree that the most effective strategies combine several approaches. They also stress that the benefits are not evenly shared. In many cities, poorer neighbourhoods have fewer trees and parks and more paved surfaces than wealthier ones, and their residents are less likely to have air conditioning. As a result, the people who are most exposed to extreme heat are often those least able to protect themselves from it.

You should spend about 20 minutes on Questions 27–40, which are based on Reading Passage 3 below.

Do animals have culture?

For much of the twentieth century, culture was regarded as something uniquely human. Animals, it was assumed, behaved as they did because of their genes or because of the environment in which they lived, while humans alone passed on knowledge, skills and traditions from one generation to the next through learning. Over the past few decades, however, this assumption has been seriously challenged, and many scientists now accept that at least some animals have cultures of their own. The question of what exactly that means, though, remains the subject of lively debate.

One of the earliest and best-known examples comes from Koshima, a small island off the coast of Japan. In 1953, researchers studying a group of Japanese macaques, who had been providing the monkeys with sweet potatoes on the beach, noticed that a young female had begun washing the sand off her potatoes in a stream. Over the following years, the behaviour spread, first to her playmates and relatives and then to most of the group, and the monkeys later began washing their potatoes in the sea, apparently because they liked the taste of the salt. Older males, who had less contact with the young monkeys, were the slowest to adopt the habit.

Perhaps the strongest evidence for animal culture comes from chimpanzees. In 1999, a team of researchers who had studied chimpanzees at seven sites across Africa published a comparison of their behaviour. They identified 39 behaviours, including ways of using tools, grooming and courting, that were common in some communities but absent in others, and that could not be explained by differences in the environment. Chimpanzees in some areas of West Africa, for example, use stones as hammers to crack open nuts, while those in other areas, where the same nuts and stones are available, do not. The researchers argued that the pattern of differences resembled the variation found between human cultures.

Some of the most striking examples come from the sea. Male humpback whales sing long, complex songs during the breeding season, and all the males in a population sing roughly the same song, which gradually changes over time. Researchers studying humpback whales in the South Pacific found that new songs regularly appeared in the populations off eastern Australia and then spread eastwards from one population to the next across the ocean over a period of about two years, in a series of what they described as cultural revolutions. Killer whales, meanwhile, live in groups that differ in their calls, their diet and their hunting techniques, even when they share the same waters.

Sceptics have questioned whether these behaviours really deserve to be called culture. Some argue that apparent differences between groups may in fact have genetic causes, or may result from small differences in the environment that researchers have failed to notice. Others point out that true culture, in the human sense, involves more than simply copying others: human cultures accumulate changes over time, with each generation building on the achievements of the last, so that no single individual could ever invent them alone. There is little evidence that animal traditions become more complex in this way.

To address the first of these objections, researchers have turned to experiments. In one well-known study, scientists taught a single chimpanzee in each of two groups a different method of obtaining food from a puzzle box, while a third group had no trained member. When the trained chimpanzees returned to their groups, the method each had learned spread among the other animals, and most of them continued to use it even after discovering the alternative. The untrained group, meanwhile, largely failed to solve the problem. Such experiments make it difficult to argue that the behaviour is determined by genes or by the environment alone.

The debate is not only of academic interest. If animals have cultures, this has important implications for conservation. A population that has lost its older members may also have lost knowledge, such as migration routes or the locations of water sources in times of drought, that cannot easily be recovered. Animals raised in captivity and released into the wild may lack the skills that their wild relatives learn from one another. In 2014, an international agreement on the conservation of migratory species recognised for the first time that cultural knowledge should be taken into account when protecting whales and dolphins.

None of this means that animal cultures are equivalent to human ones. The richness of human culture, with its languages, technologies and institutions, remains unmatched. But the evidence suggests that the capacity for culture did not appear suddenly in our own species. Instead, it seems to have deep roots in the animal world, and studying those roots may help us to understand how our own remarkable cultural abilities evolved.