IELTS Academic Reading — Practice Test 18

Few advances have done more to lengthen human lives than the discovery of antibiotics. Before they became widely available in the 1940s, a scratch could turn septic and kill, and routine operations carried a real risk of fatal infection. Antibiotics changed all this by killing bacteria or preventing them from multiplying. Yet from the very beginning their pioneers warned that the triumph might not last. Bacteria reproduce with extraordinary speed, and among the billions in any population a few will, purely by chance, carry a trait that lets them survive a drug that kills the rest. Resistance, in other words, is not an accident but an entirely predictable product of evolution — and the more heavily a drug is used, the faster it emerges.

The mechanics of the process are now well understood. When a population of bacteria meets an antibiotic, the few individuals that happen to resist it survive and multiply, passing their advantage to their descendants; within a few generations the resistant strain dominates. What makes bacteria especially formidable is a second route. Unlike animals and plants, they can swap fragments of genetic material directly with their neighbours, even across different species, through a process known as horizontal gene transfer. A resistance gene that arises in a harmless gut bacterium can therefore be handed to a dangerous one, so that resistance spreads not only down the generations but sideways, through whole communities of microbes at once.

Much of the blame for accelerating this natural process lies with how the drugs are used in medicine. For decades antibiotics were prescribed freely, often for complaints they could not touch: viral infections such as colds and influenza, against which they are wholly useless. Patients, too, have played a part, stopping a course as soon as they feel better and leaving behind the hardier bacteria that a full course would have finished off. Every unnecessary or incomplete treatment applies evolutionary pressure without securing any benefit, effectively training bacterial populations to withstand the very weapons meant to defeat them.

Medicine, however, is not the largest consumer of these drugs. In many countries the majority of antibiotics are given not to people but to farm animals — cattle, pigs and poultry — and not primarily to treat disease. Low doses added routinely to feed were found decades ago to make animals grow faster, and the practice became widespread on intensive farms. Because the animals are healthy, this exposes vast bacterial populations to just enough of a drug to favour resistant strains without wiping them out — close to ideal conditions for breeding resistance. Resistant bacteria can then reach humans through food, water or direct contact, which is why a growing number of governments have moved to ban the use of antibiotics purely for growth promotion.

One might expect the pharmaceutical industry to respond by developing new antibiotics, but here economics works against public health. A new antibiotic, once approved, is deliberately held in reserve and used as sparingly as possible to slow the emergence of resistance — which means it earns very little. A drug for a chronic condition such as high blood pressure, by contrast, may be taken daily for decades. Faced with this imbalance, most large companies have abandoned antibiotic research altogether, and the pipeline of genuinely new compounds has slowed to a trickle. The result is a paradox: the drugs society most urgently needs are the ones it is least profitable to make.

There is, nonetheless, much that can be done, and the most immediate measures cost relatively little. Stewardship programmes, which restrict antibiotics to cases where they are genuinely needed and match the drug precisely to the infection, have already slowed resistance in hospitals that adopt them. Rapid diagnostic tests, able to establish within hours whether an infection is bacterial and which drug will defeat it, would spare countless unnecessary prescriptions; at present a doctor often has to guess. Better surveillance, tracking where resistant strains appear and how they travel, allows outbreaks to be contained before they spread. None of these measures is glamorous, but together they buy time.

Buying time matters, because the problem cannot be solved by any single country or profession acting alone. Bacteria ignore borders, travelling with people, animals and goods, so a resistant strain that emerges on one continent may within months appear on another. This has prompted calls for a 'One Health' approach that treats human medicine, animal husbandry and the environment as a single connected system rather than as separate compartments. Some researchers pin their hopes on entirely new strategies — viruses that prey on bacteria, or drugs that disarm rather than kill them — but these remain largely experimental. For now, the realistic goal is not to defeat resistance, which evolution guarantees, but to manage it wisely enough that antibiotics keep working.

Every human society changes over time. The tools people use, the words they speak, the songs they sing and the beliefs they hold are not fixed but drift, generation by generation, into new forms. For most of history such change was simply described, not explained. Over the past half-century, however, a growing body of researchers has proposed that cultural change is not merely analogous to biological evolution but governed by the same underlying logic. Just as living things evolve when heritable variations are passed on at different rates, they argue, so too do ideas and practices. A catchy tune, a useful technique or a persuasive story spreads through a population while its rivals fade, and the accumulated result, over centuries, is the gradual transformation we call cultural history. The claim is bold, and it has provoked as much resistance as enthusiasm.

The appeal of the theory lies in its economy. Darwin's account of biological evolution rests on three ingredients: variation among individuals, inheritance of that variation, and differences in the rate at which variants are passed on. Wherever these three conditions hold, its defenders point out, evolution of some kind must follow — and culture appears to satisfy all three. Ideas vary; they are transmitted from person to person by imitation and teaching; and some are transmitted more successfully than others. In 1976 the biologist Richard Dawkins coined the word 'meme' for such a unit of cultural inheritance, a counterpart to the gene, imagining ideas as entities that compete to copy themselves into human minds. The term caught the public imagination, though many scholars have since found it more suggestive than rigorous.

For all its elegance, the analogy has drawn sharp criticism, and the sharpest objection concerns the matter of copying. Genes are replicated with remarkable fidelity: a gene is passed on as a near-perfect copy, and errors are rare. Cultural transmission, critics argue, is nothing like this. When a story passes from one teller to the next, it is not copied but reconstructed, filtered through the memory, understanding and purposes of each person who receives it. Every transmission is therefore an act of transformation, and over a chain of retellings the original may be altered beyond recognition. If there is no faithful replicator at the heart of the process, these critics conclude, then culture lacks the very thing that makes biological evolution work, and the comparison is at best a loose metaphor rather than a genuine science.

Defenders of the field have a ready reply. Perfect copying, they insist, is not required; what matters is that enough of the variation survives transmission for selection to act upon. A learner need not reproduce a skill exactly, only closely enough that its useful features tend to persist while others drop away. Moreover, several psychological tendencies push cultural transmission towards stability. People preferentially copy the majority, or imitate those who are successful or admired, and such biases can preserve a practice across many generations even when individual copies are imperfect. Mathematical models built on these assumptions, its proponents note, successfully predict how real customs spread and endure — a practical achievement that, they contend, no purely metaphorical account could deliver.

Even its strongest advocates concede, however, that cultural evolution departs from the biological kind in important ways. Biological inheritance flows in one direction, from parent to offspring; cultural inheritance can flow sideways between unrelated individuals, and even backwards, from the young to the old. Genetic mutations are blind, arising without regard to what would be useful; cultural variations are often deliberate, invented on purpose to solve a particular problem. And where a genetic change can spread through a population only across many generations, a cultural one — a new technology, say — can sweep through a society within a single lifetime. In these respects culture resembles less the slow, undirected process Darwin described than the discredited theory of his predecessor Lamarck, in which characteristics acquired during life are passed on to the next generation.

The two kinds of evolution are not, in any case, wholly separate; at times they visibly shape each other. The clearest example concerns the digestion of milk. Most mammals lose the ability to digest lactose, the sugar in milk, after infancy, and for most of human history adults did too. But in populations that took up dairy farming, individuals who happened to retain that ability into adulthood enjoyed a nutritional advantage, and over a few thousand years the relevant gene became common among them. Here a cultural practice — keeping animals for their milk — altered the pressures of natural selection and changed the genetic make-up of a population. This two-way interaction, in which culture reshapes biology and biology constrains culture, is now studied under the name of gene-culture coevolution.

Whether all this amounts to a unified science or merely an illuminating set of analogies remains genuinely contested. Sceptics maintain that borrowing the vocabulary of biology dresses up ordinary historical description in misleading finery, adding the prestige of Darwin without his predictive power. Enthusiasts counter that the approach has already yielded testable claims and quantitative models that conventional history never attempted. What is not in dispute is that the questions the field raises are real: why some ideas spread and others vanish, why certain practices persist for millennia, and why human beings, alone among animals, have accumulated a body of knowledge and custom that grows richer with each generation. The answers may not fit neatly into a Darwinian frame — but the frame has at least made the questions impossible to ignore.