Once expelled, the algae can no longer provide the coral with the nutrients and pigments it needs to survive.

Prolonged or repeated bleaching events, however, typically lead to widespread coral mortality and the collapse of reef ecosystems.

Coral bleaching occurs when environmental stressors cause reef-building corals to expel the symbiotic algae living within their tissues.

If temperatures return to normal within a few weeks, the algae may recolonise and the coral can recover.

Rising sea surface temperatures, driven by global climate change, are the most widespread trigger of this phenomenon worldwide.

This rapid proliferation of printed material contributed directly to rising literacy rates across all social classes.

Johannes Gutenberg's press, developed in Mainz around 1440, made it possible to produce books at a fraction of the cost of hand-copying.

Historians have argued that without this technological shift, the intellectual movements of the Renaissance and the Reformation would have unfolded very differently.

The introduction of movable-type printing in fifteenth-century Europe marked a decisive turning point in the history of knowledge dissemination.

Within decades, printing houses had appeared in every major European city, dramatically expanding the availability of written texts.

This mechanism, while theoretically straightforward, operates with significant time lags that make precise timing of rate decisions notoriously difficult.

Higher interest rates make borrowing more expensive, which tends to reduce consumer spending and business investment.

As spending contracts, upward pressure on prices gradually eases, bringing inflation back toward the target.

Central banks use interest rate adjustments as their primary tool for managing inflation and stabilising the economy.

When inflation rises above the target range, the central bank typically raises its benchmark rate to cool demand.

Critically, the theory predicts that the strength of this bias increases when the group's status or identity is perceived to be under threat.

These findings have informed policies aimed at reducing intergroup conflict, though translating laboratory results into real-world interventions remains a persistent challenge.

Once a person identifies with a particular group, they tend to favour members of that group over outsiders, even when group membership is assigned arbitrarily.

Social identity theory, first articulated by Henri Tajfel in the 1970s, proposes that individuals derive a significant portion of their self-concept from the groups to which they belong.

This in-group bias has been demonstrated in numerous experimental settings, from the minimal group paradigm to large-scale surveys of ethnic and national identification.

Once the DNA is severed, the cell's natural repair mechanisms can be harnessed to delete, replace, or insert genetic material at that site.

Consequently, a major area of ongoing research focuses on developing modified versions of Cas9 that minimise these off-target effects while retaining the system's efficiency.

The system works by using a guide RNA molecule to direct the Cas9 enzyme to a specific location in the genome, where it makes a precise cut in the DNA strand.

Despite its precision, the technique still carries risks of off-target edits — cuts made at unintended genomic locations — which pose significant safety concerns for clinical applications.

CRISPR-Cas9, a molecular tool adapted from a naturally occurring bacterial defence mechanism, has transformed the field of genetic engineering since its first application in 2012.

These structural challenges were compounded by Cold War rivalries, as both the United States and the Soviet Union competed for influence over the newly independent states.

The wave of decolonisation that swept across Africa in the 1960s reshaped the political map of the continent in barely two decades.

In many cases, however, independence was followed by prolonged instability, as newly formed governments struggled to establish legitimacy across ethnically diverse populations.

Several colonial powers, weakened by the Second World War and facing mounting international pressure, began negotiating the transfer of power to local political movements.

Understanding this post-independence trajectory is essential for making sense of the political and economic conditions that continue to shape many African nations today.

For example, studies have demonstrated that individuals tend to overvalue immediate gratification over long-term benefits, a tendency known as present bias.

Traditional economic models assume that individuals make decisions rationally, weighing costs and benefits to maximise their utility.

The concept of 'nudging' — designing choice architectures that gently steer people toward better decisions without restricting their freedom — has since been adopted by governments worldwide.

Whether such interventions represent a legitimate use of state influence or an infringement on personal autonomy remains a subject of ongoing debate among scholars and policymakers alike.

Behavioural economists, drawing on insights from psychology, have shown that systematic cognitive biases routinely cause people to deviate from these predictions.

Research suggests, however, that the relationship between density and social isolation is far more complex than this simple narrative implies.

Policymakers seeking to promote social cohesion in rapidly growing cities would therefore benefit from focusing on the design of shared public spaces rather than on population density alone.

In some high-density neighbourhoods, close physical proximity actually strengthens community ties by facilitating frequent informal interactions among neighbours.

A common assumption is that such extreme population density inevitably erodes social bonds and fosters alienation among residents.

Rapid urbanisation in the developing world has created cities that house millions of people within a remarkably small geographic footprint.

Importantly, emerging research indicates that the microbiome also trains and modulates the immune system, helping it distinguish between harmful pathogens and benign substances.

Perturbations to this microbial community — whether caused by antibiotics, diet, or infection — have been linked to a range of chronic conditions, including inflammatory bowel disease and obesity.

The human gut harbours trillions of microorganisms collectively known as the gut microbiome, which plays a fundamental role in maintaining overall health.

Among its many functions, the microbiome assists in the digestion of complex carbohydrates and synthesises essential vitamins that the human body cannot produce on its own.

These findings have spurred a rapidly growing field of microbiome-targeted therapies, though the sheer complexity of microbial interactions means that clinical applications remain in their early stages.

Critics of this framework argue, however, that the rise of transnational challenges — from climate change to global pandemics — has exposed the limits of a system built on rigid territorial sovereignty.

This principle of non-interference, combined with the notion of legal equality among states, became the organising logic of European diplomacy for the next three centuries.

Subsequent international law, including the United Nations Charter, has built upon these Westphalian principles, embedding them in the architecture of global governance.

The Peace of Westphalia, signed in 1648, is widely regarded as the foundational moment in the development of the modern state system.

By ending the Thirty Years' War and recognising the sovereignty of individual states over their own territories, the treaties established the principle that no external authority could legitimately interfere in a state's internal affairs.