Part 1
Read the text and answer questions 1–13.

Earth’s lakes are under threat

A
Lake Poopo used to be Bolivia’s second largest lake. Situated in the Altiplano Mountains at an altitude of around 3,700m, the lake in winter would cover an area of some 2,700 square kilometres as it was fed by swollen rivers. With very little rainfall during summer, this reduced to around 1,000, still a remarkable size. This was the pattern in previous centuries, but in December 2015, satellites confirmed the reports of local people that the lake had gone. While scientists had suspected that Poopo would eventually run dry, they didn’t expect that this would occur for at least another thousand years. The local mining industry had already contributed to the pollution of the lake, but scientists believe global warming, drought and irrigation projects are all responsible for its disappearance. Today the consequences of Lake Poopo’s disappearance are dramatic; many people who lived in the villages around it have left, since there are no more fish to be caught. Environmentalists also point to the fact that the lake had been the stopover point for thousands of birds as they migrated to other regions. Their numbers will certainly fall now the lake has gone.

B
Lake Poopo is not the only vast are of water to have disappeared. The Aral Sea in Central Asia was once the world’s fourth largest lake but then it began to shrink in the 1960s. As a shallow lake, it depended on rivers to keep its level up. But then water from these rivers was diverted for irrigation purposes. Rice is a crop that needs huge quantities of water to survive in desert areas. Fields planted with cotton also require a regular supply. Now the water level is so low that fishing has stopped altogether. And it is not just the immediate area that is affected. Because the floor of the lake is now exposed, the salt that lies there is often carried by the wind across a radius of 300 kilometres. This impacts on agriculture as it damages growing plants and is absorbed by the soil.

C
For some lakes, the biggest threat is from climate change. On average, the surface water of the world’s lakes has gone up in temperature by 0.34° C every ten years since 1985. Lake Tanganyika in East Africa is a lake where this trend has been observed, although it is by no means the most extreme example. This would be Lake Fracksjon in Sweden, where an increase of 1.35° C per decade has been observed – a figure which is estimated to rise. For Lake Tanganyika, however, the consequences have been severe. Warming has disrupted its ecosystem, and fish numbers have dropped sharply. In turn, this decline in fish stocks has impacted on families living in villages and towns around the lake, since they have no other source of protein. Furthermore, around 100,000 people depend on the fisheries established around the Lake Tanganyika. These companies provide them with regular employment, without which communities will not survive.

D
In Iran, Lake Urmia’s waters have also been affected by unusually hot summers, but dams and irrigation projects have also played a part. In the past, people admired its beautiful green-blue colour. However, the water now has a red tint. The reason for this is that bacteria quickly multiply in the warm waters of a shallow lake. Now local communities are understandably concerned about the future. One of their concerns is that Lake Urmia is no longer seen as a place where people can bathe to improve their health. As a result, in the last decade, there has been a downturn in tourism in the area, an industry many people depended on.

E
In some cases, it can be a challenge for scientist to predict outcomes for a lake or to recognise the factors that threaten it. Take, for example, Lake Waiau in Hawaii, a lake that was used in healing rituals by native Hawaiians. It is a fairly small lake, approximately 100m across, with some variation as the water level rises and falls. However, in early 2010, the lake began to decrease in size. By September 2013, it could only be described as a pond. The cause of the lake’s decline has not yet been established, but drought is among the suspects. Then there is Scott Lake in central Florida. In June 2006 a massive sinkhole opened up beneath the lake – acting like a plug hole in a bath. It only took two weeks for the water to drain away. Local residents called meetings to decide what action to take, but in the end, nature took care of the problem. Clay, sand and other fine material plugged the hole and the lake started to fill with water again. Nevertheless, as geologists point out, sinkholes can occur with some frequency in Florida so there is a chance that Scott Lake will drain away again.

Part 2
Read the text and answer questions 14–26.

Art to the aid of technology

What caricatures can teach us about facial recognition, by Ben Austen

A
Our brains are incredibly agile machines, and it is hard to think of anything they do more efficiently than recognize faces. Just hours after birth, the eyes of newborns are drawn to facelike patterns. An adult brain knows it is seeing a face within 100 milliseconds, and it takes just over a second to realize that two different pictures of a face, even if they are lit or rotated in very different ways, belong to the same person.

B
Perhaps the most vivid illustration of our gift for recognition is the magic of caricature-the fact that the sparest cartoon of a familiar face, even a single line dashed off in two seconds, can be identified by our brains in an instant. It is often said that a good caricature looks more like a person than the person themselves. As it happens, this notion, counterintuitive though it may sound, is actually supported by research. In the field of vision science, there is even a term for this seeming paradox-the caricature effect-a phrase that hints at how our brains misperceive faces as much as perceive them.

C
Human faces are all built pretty much the same: two eyes above a nose that’s above a mouth, the features varying from person to person generally by mere millimetres. So what our brains look for, according to vision scientists, are the outlying features-those characteristics that deviate most from the ideal face we carry around in our heads, the running average of every “visage” we have ever seen. We code each new face we encounter not in absolute terms but in the several ways it differs markedly from the mean. In other words, we accentuate what is most important for recognition and largely ignore what is not. Our perception fixates on the upturned nose, the sunken eyes or the fleshy cheeks, making them loom larger. To better identify and remember people, we turn them into caricatures.

D
Ten years ago, we all imagined that as soon as surveillance cameras had been equipped with the appropriate software, the face of a crime suspect would stand out in a crowd. Like a thumbprint, its unique features and configuration would offer a biometric key that could be immediately checked against any database of suspects. But now a decade has passed, and face-recognition systems still perform miserably in real-world conditions. Just recently, a couple who accidentally swapped passports at an airport in England sailed through electronic gates that were supposed to match their faces to file photos.

E
All this leads to an interesting question. What if, to secure our airports and national landmarks, we need to learn more about caricature? After all, it’s the skill of the caricaturist-the uncanny ability to quickly distill faces down to their most salient features-that our computers most desperately need to acquire. Clearly, better cameras and faster computers simply aren’t going to be enough.

F
At the University of Central Lancashire in England, Charlie Frowd, a senior lecturer in psychology, has used insights from caricature to develop a better police-composite generator. His system, called EvoFIT, produces animated caricatures, with each successive frame showing facial features that are more exaggerated than the last. Frowd’s research supports the idea that we all store memories as caricatures, but with our own personal degree of amplification. So, as an animated composite depicts faces at varying stages of caricature, viewers respond to the stage that is most recognizable to them. In tests, Frowd’s technique has increased positive identifications from as low as 3 percent to upwards of 30 percent.

G
To achieve similar results in computer face recognition, scientists would need to model the artist’s genius even more closely-a feat that might seem impossible if you listen to some of the artists describe their nearly mystical acquisition of skills. Jason Seiler recounts how he trained his mind for years, beginning in middle school, until he gained what he regards as nothing less than a second sight. ‘A lot of people think that caricature is about picking out someone’s worst feature and exaggerating it as far as you can,’ Seiler says. ‘That’s wrong. Caricature is basically finding the truth. And then you push the truth.’ Capturing a likeness, it seems, has less to do with the depiction of individual features than with their placement in relationship to one another. ‘It’s how the human brain recognizes a face. When the ratios between the features are correct, you see that face instantly.’

H
Pawan Sinha. director of MIT’s Sinha Laboratory for Vision Research, and one of the nation’s most innovative computer-vision researchers, contends that these simple, exaggerated drawings can be objectively and systematically studied and that such work will lead to breakthroughs in our understanding of both human and machine-based vision. His lab at MIT is preparing to computationally analyze hundreds of caricatures this year, from dozens of different artists, with the hope of tapping their intuitive knowledge of what is and isn’t crucial for recognition. He has named this endeavor the Hirschfeld Project, after the famous New York Times caricaturist Al Hirschfeld.

I
Quite simply, by analyzing sketches, Sinha hopes to pinpoint the recurring exaggerations in the caricatures that most strongly correlate to particular ways that the original faces deviate from the norm. The results, he believes, will ultimately produce a rank-ordered list of the 20 or so facial attributes that are most important for recognition: ‘It’s a recipe for how to encode the face,’ he says. In preliminary tests, the lab has already isolated important areas-for example, the ratio of the height of the forehead to the distance between the top of the nose and the mouth.

J
On a given face, four of 20 such Hirschfeld attributes, as Sinha plans to call them, will be several standard deviations greater than the mean; on another face, a different handful of attributes might exceed the norm. But in all cases, it’s the exaggerated areas of the face that hold the key. As matters stand today, an automated system must compare its target faces against the millions of continually altering faces it encounters. But so far, the software doesn’t know what to look for amid this onslaught of variables. Armed with the Hirschfeld attributes, Sinha hopes that computers can be trained to focus on the features most salient for recognition, tuning out the others. ’Then.’ Sinha says, ’the sky is the limit’.

Part 3
Read the text and answer questions 27–40.

Mystery of the Mummies

In 1992, a German scientist made a discovery which was to upset whole areas of scientific study from history and archeology to chemistry and botany. Dr. Svetlana Balabanova, a forensic specialist, was performing tissue tests on an Egyptian mummy, part of a German museum collection. The mummified remains were of a woman named Henut-Tauiwho had died over 3000 years ago. Amazingly, the tests revealed that her body contained large quantities of cocaine and nicotine. Dr. Balabanova had regularly used the same testing methods to convict people of drug consumption but she had not expected to find nicotine and coca in an Ancient Egyptian mummy. It is generally accepted that these two plants, native to the Americas did not exist on other continents prior to European exploration.

Dr. Balabanova repeated the tests then sent out fresh samples to three other labs. When the results came back positive she published a paper with two other scientists. If Balabanova was shocked by the results of her tests she was even more shocked at the hostile response to her publication. She received many insulting letters, accusing her of fraud.

There were two explanations that came immediately to mind. One was that something in the tests could have given a false result. The second was that the mummies tested were not truly Ancient Egyptian. Perhaps they were relatively modern bodies, containing traces of cocaine. Dr. Balabanova then examined tissue from 134 naturally preserved bodies over a thousand years old discovered in an excavated cemetery in the Sudan. About a third of them tested positive for nicotine or cocaine.

But something had happened even earlier which should have initiated serious discussion. In 1976 the mummified remains of Ramses II arrived in Paris for repair work. Dr. Michelle Lescot of the Natural History Museum (Paris) was looking at sections of bandages and within the fibres found a plant fragment. When she checked it under a microscope she was amazed to discover that the plant was tobacco. Fearing that she had made some mistake she repeated her tests again and again with the same result every time: a New World plant had been found on an Old World mummy. The results caused a sensation in Europe. Was it possible that a piece of tobacco had been dropped by chance from the pipe of some forgotten archaeologist? Dr. Lescot responded to this charge of contamination by carefully extracting new samples from the abdomen, with the entire process recorded on film. These samples, which could not be ‘droppings’, were then tested. Once again they were shown to be tobacco.

The discovery of tobacco fragments in the mummified body of Ramses II should have had a profound influence upon our whole understanding of the relationship between Ancient Egypt and America but this piece of evidence was simply ignored. It raised too many questions and was too far outside of commonly accepted scientific views.

So now the question had returned. Could Ancient Egyptian trade have stretched all the way across the Atlantic Ocean? This was an idea so unbelievable it could only be considered after all the other possibilities had been eliminated, Could Egyptians have obtained imports from a place thousands of miles away, from a continent supposedly not discovered until thousands of years later? Was it possible that coca — a plant from South America had found its way to Egypt 3,000 years ago? If the cocaine found in mummies could not be explained by contamination, or fake mummies or by Egyptian plants containing it, there appeared to be another interesting possibility: a trade route with links all the way to the Americas.

The Egyptians did make great efforts to obtain incense and other valuable plants used in religious ceremonies and herbal medicines, but to the majority of archeologists, the idea is hardly worth talking about. Professor John Baines, an Egyptologist from Oxford University states: ‘I don’t think it is at all likely that there was an ancient trade network that included America. The essential problem with any such idea is that there are no artefacts found either in Europe or in America.’ But other experts aren’t so sure. Professor Martin Bernal, a historian, from Cornell University says, ‘We’re getting more and more evidence of world trade at an earlier stage. You have the Chinese silk definitely arriving in Egypt by 1000 BC.’ In his opinion, it is arrogance on the part of modern people to believe that a transoceanic trading network could only have been set up in recent times.

The discoveries in the mummies from Egypt and Sudan have challenged conventional beliefs. It is no longer possible to exclude the hypothesis of transoceanic trade in ancient times. The tale of HenutTaui and the story of Ramses II show that, in science, facts can be rejected if they don’t fit with our beliefs, while what is believed to be proven, may actually be uncertain. It is understandable then, how a story of a scientist, a few mummies and some routine tests, could upset whole areas of knowledge we thought we could take for granted.