Reading — 2026 May–Aug Recall Set 23

Hervé Bocherens, an evolutionary biologist at the University of Tübingen, Germany, says his colleagues find his research methods a little ‘crude’. He dissolves 30,000-year-old animal bones in hydrochloric acid, which is strong enough to burn through metal, soaks the bone solution in lye, cooks it at about 200 degrees Fahrenheit and freeze-dries it, until what’s left is a speck of powder weighing less than one one-hundredth of an ounce. The method may be harsh, but the yield is precious – the biography of a cave bear as told through its chemical components. Bocherens is at the forefront of research on the bear, a European species that died out 25,000 years ago. People have been excavating cave bear remains for hundreds of years— in the Middle Ages, the massive skulls were attributed to dragons — but the past decade has seen a burst of discoveries about how the bears lived and why they became extinct. An abundance of bones has been found from Spain to Romania in caves where the animals once hibernated. ‘Caves are good places to preserve bones, and cave bears had the good sense to die there,’ Bocherens says. Along with mammoths, lions and woolly rhinos, cave bears (Ursus spelaeus) were once among Europe’s most impressive creatures. Males weighed up to 1,500 pounds, 50 per cent more than the largest modern grizzly bears. Cave bears had wider heads than today’s bears, and powerful shoulders and forelimbs. But the relationship between humans and cave bears has been mysterious. Were humans prey for the bears, or predators? Were bears the object of worship or fear? Initially cave bears shared the continent of Europe, more than 100,000 years ago, with Neanderthals, a primitive species of humans. Modern humans arrived in Europe about 40,000 years ago, and were soon aware of the bears. They painted images of the animals on cave walls, and carved their likeness in fragments of mammoth tusk. The walls of France’s Chauvet cave are painted with lions, hyenas and bears; dating back 32,000 years, these are perhaps the oldest paintings in the world. The painters weren’t the cave’s only occupants: the floor is covered with 150 cave bear skeletons, and its soft clay still holds paw prints. Most dramatically, a cave bear skull was perched on a stone slab in the center of one chamber, placed deliberately by some long-gone cave inhabitant. ‘There’s no way to tell if it was just curiosity that made someone put a skull on the rock, or if it had religious significance,’ says Bocherens. Another discovery, hundreds of miles to the east of Chauvet, would shed light on the relationship between cave bears and humans. The Swabian Jura is a limestone plateau in southwestern Germany that is riddled with caves. A steel gate guards the Hohle Fels cave from vandals and curiosity-seekers. Floodlights in the cave’s main chamber illuminate the ceiling, vaulted like a cathedral above 5,000 square feet of floor space. Long ago, as shown by the bones and tools that archaeologists have found, cave bears and human beings sought shelter here from winter weather. In 2000, University of Tübingen paleobiologist Susanne Münzel unearthed a bear vertebra with a tiny triangular piece of flint embedded in it. The flint was likely a broken spear point, hard evidence of a successful bear hunt 29,000 years ago. Münzel also found bear bones that had clearly been scraped by stone tools. Evidence for bears being a food source for early humans was shown by cut marks on skulls and leg bones where the flesh had been cut away. Many of the bones were from baby bears, perhaps caught while hibernating. Cave bears disappeared not long after humans spread throughout Europe, and one theory is that hunting led to the bears’ extinction. Hervé Bocherens’ test tubes may hold the clues. Running his white powder through a mass spectrometer, he identifies different isotopes, or chemical forms, of elements such as carbon and nitrogen that reflect what the bears were eating and how quickly they grew. After studying hundreds of bones from dozens of sites in Europe, Bocherens has found that cave bears ate mainly plants. This would have made bears particularly vulnerable to the last Ice Age, which began around 30,000 years ago. This Ice Age shortened or eliminated growing seasons, and altered the distributions of plant species across Europe. Cave bears began to move from their old territories, according to a DNA analysis of teeth found near the Danube River. The cave bear population there was relatively stable, with the same genetic patterns showing up generation after generation. But about 28,000 years ago, newcomers with different DNA patterns arrived — a possible sign of hungry bears suddenly on the move. But changes in the climate can’t be solely to blame for the bears’ extinction. According to the latest study, by Erik Trinkaus and his colleagues at the Max Planck Institute, cave bear populations began a long, slow decline 50,000 years ago — well before the climate began to change. The new study supports a different explanation for the cave bears’ demise. As Neanderthals, and then a growing population of modern humans moved into the caves of Europe, cave bears had fewer safe places to hibernate. An acute housing shortage may have been the final blow for these magnificent beasts.

A The term ‘graffiti’ derives from the Italian word graffio meaning ‘scratching’, and can be defined as uninvited markings or writing scratched or applied to objects, built structures, and natural features. It is not a new phenomenon; examples can be found on ancient structures around the world, in some cases predating the Greeks and Romans. In such circumstances, it has acquired invaluable historical and archaeological significance as it provides a social history of life and events at that time. This is not true of more recent graffiti, which has become a pervasive problem particularly over the last 50 years, as a result of the availability of cheap and quick means of mark-making. These include the ubiquitous spray paints. B Graffitists, the people who are responsible for creating graffiti, are indiscriminate about the surfaces they choose. Wherever graffiti appears, it is usually considered a priority to remove it as quickly as possible. One reason for this is to prevent ‘copy-cat’ emulation, which can occur rapidly once a clean surface is defaced, and so many companies and councils have a policy of removing graffiti within an hour or two of it being reported. Another reason is that as paints, glues, and inks dry out, they can become increasingly difficult to remove. A more important factor, however, is that graffiti can lead to more serious forms of vandalism and, ultimately, to the deterioration of a neighborhood area, and in this way contributes to a general social decline. For this reason, the police like to be notified of new graffiti incidents. To aid in achieving a successful prosecution, they encourage owners of properties to take photographs of any new graffiti, as there could be other related incidents occurring locally. An incidence pattern can help to identify possible culprits, as can their ‘tag’—the distinctive mark graffitists leave to show the graffiti is their work. C Any proposal to remove graffiti has to be carefully considered because techniques designed for robust or utilitarian surfaces may result in considerable damage to older, more historic buildings. Consequently, as no two sites are the same, there is no one treatment which will be suitable for all situations; each site must be looked at individually. The owners of some graffiti-affected sites may wish to attempt their own treatment, whereas others may prefer to contact a specialist contractor. However, whichever course is decided on, it is important to follow a systematic approach. The first step is to carry out cleaning trials to see which method is suitable for the removal of the graffiti media used, and also which method has the least impact on the site surface. These trials should be carried out on a small unobtrusive area if possible and should always start with the least aggressive cleaning method, usually water, and stop once a successful method has been found. D Apart from water, a variety of methods can be used to remove graffiti; broadly, these are divided into chemical and mechanical systems. When using either of these systems, care must be taken with regard to protecting both passers-by and the person carrying out the graffiti removal. Chemical preparations are based on dissolving the graffiti media; these solvents can range from mild to potentially dangerous chemical ‘cocktails’. When using chemicals, it is important to wear protective clothing, take measures to minimize any run-off of potentially harmful chemicals, and avoid the drifting of aerial mists. Mechanical systems are often in the form of wire-brushing and grit blasting, which attempt to chip off the graffiti media. Operators of mechanical systems must also wear protective clothing to avoid being hurt by hard airborne particles. This method often leaves marks on a surface. E Different measures can be adopted to combat a recurring problem of graffiti. It is clear that protection measures will ultimately be more successful and less damaging than multiple removal treatments. Popular places for graffiti are often readily accessible flat surfaces where the graffiti will have an instant impact, but this is not always the case, and graffitists may scale bridges to give their work greater prominence. Possible protection measures may include a combination of floodlighting to illuminate dark areas and surveillance systems such as closed-circuit television. Research has shown that prominently placed cameras can reduce the incidence of graffiti in areas with a recurring problem. Unfortunately, the cost of any of these measures may be too high, and so physical obstacles such as fences, railings, doors, or gates can be introduced to discourage unauthorized access, though in some cases, these obstacles simply provide a new surface for graffiti. F Another strategy is to apply a removable anti-graffiti barrier-coating as a form of preventive measure. Although this will not stop graffiti being applied, it will make its removal much easier and usually only involves using water, which reduces the possibility of damage to the site surface. Barrier coatings are usually applied by brush or spray, leaving a thin veneer that essentially serves to isolate the graffiti from the surface. So, although there is no prescription for dealing with every graffiti incident, there are some steps that can be taken to minimize the impact of graffiti and to protect vulnerable surfaces.

Researchers are investigating the processes in the brain that give rise to fear in animals. The results may lead to new ways to treat human anxiety. Over the years, the majority of people acquire a range of skills for coping with frightening situations. They will attempt to placate a vexed teacher or boss and will shout and run when chased by a hostile stranger. But some individuals become overwhelmed in circumstances others would consider only minimally stressful: fear of ridicule might cause them to shake uncontrollably when called on to speak in a group, or terror of strangers might lead them to hide at home, unable to work or shop for groceries. Why do certain people fall prey to excessive fear? Ned H. Kalin and Steven E. Shelton at the University of Wisconsin–Madison are addressing this problem by identifying specific brain processes that regulate fear and its associated behaviors. Despite the availability of non-invasive computer-imaging techniques, such information is still extremely difficult to obtain in humans. Hence, they have turned their attention to another primate, the rhesus monkey. These animals undergo many of the same physiological and psychological developmental stages that humans do, but in a more compressed time span. As we gain more insight into the nature and operation of neural circuits that modulate fear in monkeys, it should be possible to pinpoint the brain processes that cause inordinate anxiety in people, and to devise new therapies to counteract it. Effective interventions would be particularly valuable if they were applied at an early age, as growing evidence suggests overly fearful youngsters are at high risk of later emotional distress. When they began their studies two decades ago, Kalin and Shelton knew that they would first have to find cues that elicit fear and identify behaviors that reflect different types of anxiety. With such information in hand, they could then proceed to determine the age at which monkeys begin to match defensive behaviors selectively to specific cues. Finally, by determining the parts of the brain that reach maturity during the same time span, they could gain clues to the regions that underlie the regulation of fear and fear-related behavior. The experiments were carried out at the University of Wisconsin–Madison. Kalin and Shelton discerned varied behaviors by exposing monkeys between six and 12 months old to three related situations. In the alone condition, an animal was separated from its mother and left by itself in a cage for ten minutes. In the no-eye-contact condition, a person stood motionless outside the cage and avoided looking at the solitary infant. In the stare condition, a person was again present and motionless but, assuming a neutral expression, peered directly at the animal. These positions are no more frightening than those that primates encounter frequently in the wild, or those that human infants meet whenever they are left at a day-care centre. In the alone condition, most monkeys became very active and emitted frequent gentle “coo” calls made with pursed lips. More than 40 years ago it was deduced that when an infant monkey is separated from its mother, it yearns to regain the closeness and security provided by nearness to the parent. These responses help to draw the mother’s attention. In contrast, in the more frightening no-eye-contact situation, the monkeys reduced their activity greatly and sometimes froze for extended periods of time. When an infant spots a potential predator, its goal shifts from attracting the mother to becoming inconspicuous. Inhibiting motion and freezing are common attempts to achieve this in many species. If the infant perceives that it has been detected, its aim shifts to warding off an attack. So the stare condition evoked a third set of responses. The monkeys made several hostile gestures: barking (forcing air from the abdomen through the vocal cords to emit a harsh, growl-like sound) and staring back. Sometimes the animals mixed the threatening displays with submissive ones, such as fear grimaces, which look something like wary grins, or grinding of teeth. Having identified three categories of defensive behaviours, Kalin and Shelton set about determining when infant monkeys first begin to apply them effectively. Several lines of work had led them to surmise that the ability to make such choices emerges when an infant is around two months old. To establish the critical period of development, they examined four groups of infant monkeys ranging in age up to 12 weeks old. The babies were separated from their mothers, left to acclimatise to a cage, and then exposed to the alone, no-eye-contact and stare conditions. All sessions were videotaped for analysis. They found that the infants in the youngest group (no more than two weeks old) engaged in defensive behaviours, but they lacked some motor control and seemed to act randomly, as if they had not noticed the human beings that were present. Babies in the two intermediate-age groups had good motor control, but their actions seemed unrelated to the test condition. Only animals in the oldest group (nine- to 12-week-old) conducted themselves differently in each situation, and their reactions were both appropriate and identical to those of mature monkeys. This finding meant motor control was not the prime determinant of selective responding and that nine to 12 weeks is the critical age for the appearance of a monkey’s ability to adaptively modulate its defensive activity to meet changing demands.