Category: MIL-OSI

Source: The Conversation – Africa – By Breyten Van der Merwe, PhD student, Stellenbosch University

“Magic mushrooms” are consumed recreationally and for medicinal purposes around the world. These fungi gained their fame as “magic” because they produce chemical compounds (called psilocybin and psilocin) which have psychedelic effects.

The most famous species of these mushrooms, due to their global distribution and ease of cultivation, is Psilocybe cubensis, known primarily from its preferred habitat of dung-laden fields. It was first described from Cuba, but is found throughout the world.

However, there has been a long-standing question about its evolutionary history. Where did it originate, and how did it move around the globe?

We described a new species of magic mushroom in South Africa and Zimbabwe, now named Psilocybe ochraceocentrata, which has allowed us to investigate this question.

Our disciplines are mycology (the study of fungi) and evolutionary biology. In a recent paper, we report on what P. ochraceocentrata may tell us about the possible wild origins of Psilocybe cubensis.

Our findings used sophisticated methods to test whether P. cubensis could have arrived in the Americas along with European colonisation and cattle, a long standing hypothesis proposed by the Mexican mycologist and ethnomycologist Gastón Guzmán. We also investigated other possible scenarios, such as dispersal by environmental factors like wind, or ancient biological means such as large herbivore or insect migration.

Before this study, P. ochraceocentrata was already regularly collected. But it was assumed either to be P. cubensis or P. natalensis, sold under the name “Natal Super Strength”.

We have created a framework of unambiguous identification. Ultimately, our work does not fully resolve the evolutionary history question. But it provides a guide for future study to fully understand where these fungi evolved and how they may have travelled the world.

Knowing the origin of a species is important as it explains how historical, geological and climate factors shape the current distribution of life on Earth. This can be important for understanding how some traits evolved in response to their environment, where a species may become invasive, or possibly where to look for closely related species with traits of interest for medicinal research.

How was the study performed?

Fieldwork conducted over decades in Zimbabwe by researcher Cathy Sharp, and further observations in South Africa, yielded multiple collections of mushrooms similar to P. cubensis. All were associated with the dung of herbivores, including animals native to Africa. Some Psilocybe mushrooms use dung as a food source.

Our work showed that these “cubensis look-a-likes” were superficially similar but differed microscopically and at a molecular level. We chose to investigate this relationship further. Our approach involved:

• field collection – studying specimens from the wild

• genomics of museum specimens (museomics) – using molecular techniques on historically important specimens

• phylogenetics – using genetic data to reconstruct how species are related through common ancestry

• molecular dating – estimating a general time frame when two species may have diverged from one another

• ecological niche modelling – predicting where a species can live based on environmental conditions.

This allowed us to study the natural history of P. cubensis and its close relative Psilocybe ochraceocentrata.

We found that P. ochraceocentrata and P. cubensis may have had a common ancestor living about 1.56 million years ago.

This corresponds with the global expansion of grasslands and the distribution of grazing herbivores. The world at this time would have been populated with migrating herbivores. Coprophilic fungi (fungi that grow on animal dung) could have moved with them globally, and then begun to evolve along independent paths.

Origin story

To complement our taxonomic and dating investigations, we wanted to see if we could find a plausible origin of P. cubensis. In previous studies, the lead author had identified that the closest relatives of P. cubensis all had native distributions across the Asian continent. There was very little overlap with species from the Americas.

With the addition of P. ochraceocentrata as the sister taxon (the closest relative), it became far more reasonable to suggest its evolutionary history is centred in Africa or Asia, not the Americas.

To test this, we used publicly available data from the popular public “citizen science” repository for biodiversity monitoring, iNaturalist. We then used mathematical modelling to hypothesise where these organisms might have occurred hundreds of thousands to millions of years ago.

Our work showed a lot of variability across time but partially favoured tropical and subtropical regions where large animals roamed. From this, we proposed a few scenarios of how P. cubensis split from the ancestor it shared with P. ochraceocentrata and became globally dispersed.

One theory is a natural disturbance via unknown animal or environmental vectors. In other words, something may have changed the environment and disrupted the population. For example, dung beetles could have eaten dung that had fungal spores in it, and could have crossed the ocean, taking the fungus with them. Or the spores may have been carried across the ocean on the wind. This is known to have happened with other fungi, such as Podospora.

Another possibility is migration via the Bering land bridge between Eurasia and the Americas. This is how many plants and animals moved between the continents.

Guzmán proposed that P. cubensis likely originated in Africa and was transported to the Americas via cattle transport during the colonisation events of the 1400s and 1500s. Our work suggests that this route was also possible.

The most likely scenario would be multiple introductions, and spore dispersal between populations in the Americas to retain genetic diversity.

What’s missing

Africa is one of the most biodiverse continents, and yet it is the most under-sampled for fungal diversity, due in part to a historical sampling bias of fungi from other parts of the world.

When it comes to Psilocybe, fewer than ten species are officially described from the African continent. Worldwide about 165 species are known.

Further studies are needed across the continent, to describe and map local fungal diversity and improve on current knowledge. Knowing more about the mushrooms that occur in a region tells us more about the ecology of the area, which is key to conservation efforts.

Natural history museums and herbariums were critical for this work and serve as an immeasurable biodiversity resource representing hundreds of years of scientific effort that both scientists and the general public can access.

– Magic mushrooms: new African species sheds light on the history of the famous fungus
– https://theconversation.com/magic-mushrooms-new-african-species-sheds-light-on-the-history-of-the-famous-fungus-279007

Source: The Conversation – Africa – By Abeer Elshater, Professor of Urban Morphology, Ain Shams University

Cities are often described as living archives of human memory. Walk through an old neighbourhood in an Islamic city like Fez in Morocco or Cairo in Egypt, and you can see layers of history in its streets and buildings. Traces of the past remain visible in everyday life.

Urban historians sometimes call this a palimpsest – a place where layers of history remain visible, like old writing faintly showing beneath new text.

But in many parts of the world today, cities are being transformed so rapidly that these historical layers are disappearing. Entire neighbourhoods and older areas are demolished and replaced with new districts, infrastructure corridors, or megaprojects. It’s a process that might remind one of French civil servant Georges-Eugène Haussmann’s dramatic demolition and reshaping of Paris in the 1800s.

Today’s speed and scale of development challenge the idea that cities grow slowly over time. Building places from scratch is often described as tabula rasa – a “blank slate” approach in which everything is cleared away and rebuilt as if nothing had existed before.

As scholars of architecture and urban design, we recently researched this tension between erasure and memory in urban design. We argue that urban transformation today cannot be understood simply as a choice between preserving the past or starting anew. Instead, cities are increasingly shaped by a complex interaction between the two.

Understanding this tension matters because it influences not only the identity and heritage of a city but also the social and cultural lives of the people who inhabit it. Our argument is grounded in the importance of understanding history to guide future development based on solutions that have been tested successfully in the past.

The myth of the blank slate

For centuries, planners and philosophers have been fascinated by the idea of the tabula rasa. In practice, however, urban space is never truly empty.

Even after buildings are demolished, the forces shaping the city remain: economic pressures, planning regulations, infrastructure networks, and political agendas. Clearing land often produces what French social theorist Henri Lefebvre described as “abstract space”. These are spaces designed mainly for efficiency, profit, or control – rather than for people’s memories or everyday life.

Modern urban renewal projects have often replaced historic districts with standardised environments such as large housing estates, business districts, or transport infrastructures. These environments can feel disconnected from local identity because the historical context that once gave the place meaning has been removed.

For example, Pruitt‑Igoe in St Louis in the US replaced dense, mixed-use neighbourhoods with high-rise public housing that ignored existing street patterns and community life. In Beirut in Lebanon, post-war reconstruction of the city centre prioritised modern commercial developments over the urban fabric and social networks that had defined it for decades.

French anthropologist Marc Augé described many of these environments as “non-places”: spaces of transit and consumption, such as airports, highways, and anonymous commercial zones. People pass through without forming lasting attachments.

Cities as layered memory

At the opposite end of the spectrum lies the idea of cities as palimpsest. Historic districts, archaeological remains, street patterns, and even place names all contribute to a layered memory. Urban designers often create designs that draw from the history of a site.

But the palimpsest approach also has limits. Preserving historical layers does not necessarily guarantee meaningful engagement with the past. Sometimes heritage becomes a form of nostalgia –replicating historical styles without understanding their social or cultural significance.

French philosopher Paul Ricoeur helps clarify this by distinguishing between two types of memory: repetition memory and reconstruction memory.

Repetition memory reproduces the past, often superficially. In Sydney, efforts to revitalise Indigenous neighbourhoods between 2005 and 2019 ended up repeating patterns of colonial land displacement.

Meanwhile, in Rio de Janeiro, the push to redevelop the waterfront for the 2014 Football World Cup and 2016 Olympics wiped out Afro-Brazilian cultural heritage. It replaced it with a sleek, futuristic vision of a global city.

More broadly, across cities in Africa, Asia and Latin America, speculative real-estate projects and investment-driven urban developments have turned land into a commodity. This has fuelled gentrification and pushed local communities to the margins.

Reconstruction memory, by contrast, uses fragments of the past to interpret and reinvent them for the present. For example, in Warsaw in Poland after the second world war, the Old Town was rebuilt. Not as an exact replica but as a carefully interpreted reconstruction, using historical paintings, archaeological evidence, and surviving fragments to evoke the city’s pre-war character. At the same time it accommodated modern needs.

Similarly, Hiroshima’s post-1945 reconstruction preserved certain ruins, such as the Genbaku Dome, while redesigning the surrounding urban fabric to create a memorial landscape. This both honours the past and supports a functional, modern city.

Moving beyond preservation vs demolition

Rather than choosing between total preservation and total erasure, urban design needs to recognise the dynamic relationship between memory and transformation.

We propose thinking about cities through what philosophers call a negative dialectic – a relationship in which two opposing forces, erasure and memory, continually reshape one another. We argue that:

• Urban clearance does not create a neutral blank slate. It produces new forms of space shaped by political and economic power.

• Historical memory is not a fixed archive. It is continually reconstructed through interpretation and design.

Understanding cities in this way opens the door to new design strategies. Instead of replicating historical forms or ignoring them entirely, designers can work with fragments, traces, and spatial relationships to generate new urban forms.

For example, in the historic centre of Lugano, Switzerland, the traditional public markets that take place on medieval streets and lake‑edge promenades have long shaped the city’s social life and spatial patterns. Today, these markets interact with contemporary cafés, restaurants and pedestrian routes. They knit together old street networks and new uses in a living urban tapestry rather than freezing them as static heritage relics.

This kind of layering, where everyday activities and historical paths inform modern public space design, shows how urban form can evolve by reintegrating historical traces into present-day life. But urban transformation today is largely driven by rapid development, erasure, and less visible forces.

This makes it essential to rethink how memory, preservation and design methods work together. It requires a shift in design practice away from established paradigms and toward more flexible, context-sensitive strategies.

Designers have tools to respond to rapidly changing urban environments in ways that remain meaningful to communities. These tools include cognitive mapping, which visualises how people perceive and move through a city; layered analysis, which examines overlapping aspects of urban life; and network thinking, which conceptualises cities as interconnected systems.

Designing cities in a rapidly changing world

The future of cities will likely involve even more rapid transformation. Urban sprawl, technological change, and shifting economic systems are already reshaping urban environments, challenging established planning models. For urban designers, this means learning to work in situations where historical precedents are incomplete or unstable.

Cities react to destruction and change in very different ways. Some take a tabula rasa approach. They wipe out communities and rebuilding from scratch, sometimes referencing the past in form or style. This happened in Warsaw’s Old Town. It was rebuilt to look like the prewar city, even though the original residents were gone. Brasília in Brazil, meanwhile, was planned entirely from scratch, clearing old settlements to create a modernist vision.

Others take a more layered, incremental approach, working with what’s already there and letting communities adapt over time.

In Harare’s Dzivarasekwa Extension, for instance, informal settlements were gradually formalised. Housing, services and land tenure were improved, but streets and social networks were preserved. Some cities mix both strategies, like Hiroshima did.

The challenge today is to design urban spaces that acknowledge history while remaining open to new possibilities. For us, the city is neither a blank slate nor a finished story but constantly rewritten through memory and change.

– Designing cities: should we build from scratch or keep history alive?
– https://theconversation.com/designing-cities-should-we-build-from-scratch-or-keep-history-alive-280071