IELTSwithJurabek

PASSAGE 2

Read the text and answer questions 14-26

Bird Migration

14 A Birds have many unique design features that enable them to perform such amazing feats of endurance. They are equipped with lightweight, hollow bones, intricately designed feathers providing both lift and thrust for rapid flight, navigation systems superior to any that man has developed, and an ingenious heat-conserving design that, among other things, concentrates all blood circulation beneath layers of warm, waterproof plumage, leaving them fit to face life in the harshest of climates. Their respiratory systems have to perform efficiently during sustained flights at altitude, so they have a system of extracting oxygen from their lungs that far exceeds that of any other animal. During the later stages of the summer breeding season, when food is plentiful, their bodies can accumulate considerable layers of fat, to provide sufficient energy for their long migratory flights.

15 B The fundamental reason that birds migrate is to find adequate food during the winter months when it is in short supply. This particularly applies to birds that breed in the temperate and Arctic regions of the Northern Hemisphere, where food is abundant during the short growing season. Many species can tolerate cold temperatures if food is plentiful, but when food is not available, they must migrate. However, intriguing questions remain.

16 C One puzzling fact is that many birds journey much further than would be necessary just to find food and good weather. Nobody knows, for instance, why British swallows, which could presumably survive equally well if they spent the winter in equatorial Africa, instead of flying several thousand miles further to their preferred winter home in South Africa's Cape Province. Another mystery involves the huge migrations performed by arctic terns and mudflat-feeding shorebirds that breed close to Polar Regions. In general, the further north a migrant species breeds, the further south it spends the winter. For arctic terns, this necessitates an annual round trip of 25,000 miles. Yet, en route to their final destination in far-flung southern latitudes, all these individuals overfly other areas of seemingly suitable habitat spanning two hemispheres. While we may not fully understand birds' reasons for going to particular places, we can marvel at their feats.

17 D One of the greatest mysteries is how young birds know how to find the traditional wintering areas without parental guidance. Very few adults migrate with juveniles in tow, and youngsters may even have little or no inkling of their parents' appearance. A familiar example is that of the cuckoo, which lays its eggs in another species' nest and never re-encounters its young. It is mind-boggling to consider that, once raised by its host species, the young cuckoo makes its way to ancestral wintering grounds in the tropics before returning single-handedly to northern Europe the next season to seek out a mate among its kind. The obvious implication is that it inherits from its parents an inbuilt route map and direction-finding capability, as well as a mental image of what another cuckoo looks like. Yet nobody has the slightest idea as to how this is possible.

18 E Mounting evidence has confirmed that birds use the positions of the sun and stars to obtain compass directions. They also seem to be able to detect the earth's magnetic field, probably due to having minute crystals of magnetite in the region of their brains. However, accurate navigation also requires an awareness of position and time, especially when lost. Experiments have shown that after being taken thousands of miles over an unfamiliar landmass, birds are still capable of returning rapidly to nest sites. Such phenomenal powers are the product of computing several sophisticated cues, including an inborn map of the night sky and the pull of the earth's magnetic field. How the birds use their instruments remains unknown, but one thing is clear: they see the world with a superior sensory perception to ours. Most small birds migrate at night and take their direction from the position of the setting sun. However, as well as seeing the sun go down, they also seem to see the plane of polarized light caused by it, which calibrates their compass. Travelling at night provides other benefits. Daytime predators are avoided and the danger of dehydration due to flying for long periods in warm, sunlit skies is reduced. Furthermore, at night the air is generally cool and less turbulent and so conducive to sustained, stable flight.

19 F Nevertheless, all journeys involve considerable risk, and part of the skill in arriving safely is setting off at the right time. This means accurate weather forecasting and utilizing favourable winds. Birds are adept at both, and, in laboratory tests, some have been shown to detect the minute difference in barometric pressure between the floor and ceiling of a room. Often birds react to weather changes before there is any visible sign of them. Lapwings, which feed on grassland, flee west from the Netherlands to the British Isles, France, and Spain at the onset of a cold snap. When the ground surface freezes, the birds could starve. Yet they return to Holland ahead of a thaw, their arrival linked to a pressure change presaging an improvement in the weather.

20 G In one instance a Welsh Manx shearwater carried to America and released was back in its burrow on Skokholm Island, off the Pembrokeshire coast, one day before a letter announcing its release! Conversely, each autumn a small number of North American birds are blown across the Atlantic by fast-moving westerly tailwinds. Not only do they arrive safely in Europe, but, based on ringing evidence, some make it back to North America the following spring, after probably spending the winter with European migrants in sunny African climes.

PASSAGE 3

Read the text and answer questions 27-40

Look - who was talking

Stephen Oppenheimer explores the origins of human speech

A When did we start talking to each other and how long did it take us to become so good at it? One view of language development, held by linguists such as Noam Chomsky and anthropologists such as Richard Klein, is that language, specifically the spoken word, appeared suddenly among modem humans a mere 35,000 to 50,000 years ago and that the ability to speak words and use syntax was recently genetically hard wired into our brains in a kind of language organ. This view of language is associated with the old idea that logical thought is dependent on words, a concept originating with Plato and much in vogue in the 19th century - that is, animals do not speak because they do not think. However, the abstract thought demonstrated in 20th century experiments with chimpanzees and bonobos put this theory in doubt.

B An alternative to the Chomskian theory is that language developed as a series of inventions. This was first suggested by the 18th century philosopher Etienne Bonnot de Condillac. He argued that spoken language had developed out of gesture language (langage d'action) and that both were inventions arising initially from the simple association between action and object. The theory sees gesture language as arising originally among apes as sounds accompanying gestures, with these sounds gradually becoming coded into words as the new skill drove its own evolution. Subsequently, coded words developed into deliberate, complex communication. Evolutionary pressures promoted the development of an anatomy geared to speech - the larynx, vocal muscles and a specific part of the brain immediately next to the part responsible for gestures.

C The view that spoken language was ultimately a cultural invention like tool-making, which then drove the biological evolution of the brain and vocal apparatus, seems obvious when you think of the development of different languages. The unique features of a language such as French clearly do not result from any physiological aspect of being French, but are the cultural possessions of the French-speaking community. Each language evolves from one generation to the next, constantly adapting itself to cope with the learning biases of each new set of young, immature minds.

D Those anthropologists and fossil experts who accept that speech started early still tend to think of language evolution as a gradual 2 million year process, with our own modem human species (homo sapiens) way out at the top. A major reason for this is the perception that brain growth among humans was gradual over a similar period. Several recent changes in the fossil evidence though, bring this into doubt.

E The first of these is a re-dating of soil layers from the famous Olduvai Gorge in East Africa, where many key fossil remains have been found. A number of big-brained human species appear to be much older than previously thought, with several specimens dating from over a million years ago. When brain sizes for all available skulls are plotted against time using the revised dates, the result is startling; the bulk of increases in brain size was over by around 1.2 million years ago, with some African human species having brain volumes easily within the modem human range by that time.

F So, we have the paradox that over the period when our brain was growing most rapidly, our material cultural development, as measured by stone tools, advanced only marginally; then, over a million years later, when the development of anatomically modem humans finally started to accelerate, artistically and technologically, our brains were actually getting smaller. The additional piece of evidence that makes this paradox all the more significant is that brain size did not just leap between human species in a direct line of ascent towards ourselves. Over the period from 2.5 to 1.5 million years ago, brains were growing more rapidly than at any time since, within all the different human species. The logical conclusion is that there must have been a unique new behaviour driving brain growth, shared between all species of humans.

G So, what was driving rapid brain growth right at the beginning, 2.5 million years ago? The answer may have been staring us in the face. Namely, that not only early humans, but their ancestors, had started the trend in the very useful skill of verbal communication. Around 2.5 million years ago, the weather took a decided turn for the worse, becoming more variable and colder and drier. The search for food became more taxing, and there would have been a real need to communicate more effectively and cope with the worsening environment in a co-operative way. The near maximum in brain size achieved by 1.2 million years ago indicates that those early ancestors could already have been talking perfectly well. Our brain, which had developed to manipulate and organise complex symbolic aspects of speech internally, could now be turned to a variety of other tasks.

H So what happened in the million-year gap after that? Why did we take so long to get to the moon? Cultural evolution aided by communication and teaching is a cumulative interactive process. If each new generation invented just one new skill or idea and passed it on with the rest to their children and cousins, you could predict exactly the same curve of cultural advance as we see from the archaeological and historical record: first very slow, then faster and faster.