Health & Science

RESEARCH accumulated by the Centre for Urban Design and Mental Health con rms it: People living in big cities are far more susceptible to mental illnesses than those living in more quiet, rural areas. Speci cally, city-dwellers are almost 40% more likely to su er from depression and other mood disorders and twice as likely to develop schizophrenia.

For decades, psychologists, philosophers, and urban planners have hypothesised as to why urban environments could be associated with poor mental health. During this time, many viable explanations have been brought forth. For one, citydwellers are routinely placed in emotional states that eat away at their psychological wellbeing, such as stress, isolation, and uncertainty. ere seems to be something about cities that brings out the worst in people regardless of whether they arrived with predetermined trauma in tow. One of the academic texts which comes closest to describing this “something” is ‘ e Metropolis and Mental Life’, an essay that was published in 1903 and written by the German sociologist Georg Simmel.

Growing up in the burgeoning metropolis of Berlin during the so-called Belle Époque, Georg Simmel did not share his contemporaries’ unwavering belief in civilisation. Where others saw society as continuously improving with the help of science and commerce, Simmel could not help but feel as though humanity had taken a wrong turn and was now paying for its mistake.

In his essay, Simmel compares living in a rural village to a big city and tries to show how each environment shapes the psychology of its inhabitants for better or worse. His central thesis is that city-dwellers, because they are exposed to so many more audiovisual stimuli than their countryside counterparts, involuntarily erect psychological defenses against their surroundings that make life less rewarding.

Likening the human nervous system to an electrical circuit, Simmel supposes that this system — if overstimulated for a prolonged period of time — will cease to function. As a result, things that once emotionally or intellectually stimulated the city-dweller quickly cease to excite them. Simmel refers to this outlook as blasé, but today, people also use the term jaded. “ e essence of the blasé attitude,” writes Simmel, “is an indi erence toward the distinctions between things. Not in the sense that they are not perceived, as is the case of mental dullness, but rather that the meaning and value of the distinctions between things... are experienced as meaningless. ey appear to the blasé person in a homogeneous, at and grey color.” e number of people which city-dwellers must interact with on a daily basis is so large that it is both impossible and impractical to develop a personal connection with every one they meet. Consequently, most interactions with others are brief and impersonal. is is in sharp contrast to the village, where inhabitants are intimately familiar with each other.

While relationships in towns are governed by emotions, those in cities are based on reason. “All emotional relationships between persons rest on their individuality,” writes Simmel, “whereas intellectual relationships deal with persons as with numbers, that is, as with elements which, in themselves, are indi erent, but which are of interest only insofar as they o er something objectively perceivable.”

Because city-dwellers are unable to establish meaningful relationships with a large number of people in their vicinity, their interactions with di erent elements of society become economic rather than communal. Consequently, the trust which city- dwellers are able to vest in one another is transferred over to the currencies they exchange instead.

Georg Simmel refers to money or currency as “the frightful leveler” because it expresses everything in the same monetary unit. Goods and services, rather than being unique to the person that provided them, acquire a value that can instantly be compared to all other things. us, the market economy, fully developed in big cities, also contributes to the city-dweller’s inability to distinguish their surroundings.

Modern cities are built on individuality, which is expressed in the specialisation of its labour as well as the nancial independence of its inhabitants. e polis, by comparison, was more like a large, small town. Rather than separating its populations into distinct economic units, these citystates promoted the notion that everyone was part of the same social institution.

As the world’s metropolises continue to grow, so too do the public health crises that fester in their bowels. “ e deepest problems of modern life,” Georg Simmel wrote more than 100 years ago, “ ow from the attempt of the individual to maintain the independence and individuality of his existence against the sovereign powers of society, against the weight of the historical heritage and the external culture and technique of life.”

When living in our cities is bad for our mental health

‘Cities are full of people we don’t know...

Why most modern humans possess Neanderthal DNA

IN her new book, Life as We Made It: How 50,000 Years of Human Innovation Re ned — and Rede ned — Nature, biologist Beth Shapiro explores the many ways humans have shaped nature over the millennia.

By 700,000 years ago, lineages belonging to the genus Homo were distributed from the southern tip of Africa northward and across Europe and Asia. ey were sophisticated tool users with large brains and dexterous hands, and they had begun to manipulate the world around them. After that, the fossil evidence points to a scenario something like this: Homo erectus gave rise to Homo heidelbergensis, who spread across Africa and into Europe and lived from around 700,000 years ago until around 200,000 years ago. Homo heidelbergensis gave rise to our cousins, Homo neanderthalensis, or Neanderthals, by 400,000 years ago and probably in Europe or the Middle East, and to us, Homo sapiens, in Africa by 300,000 years ago.

Today, every described Homo lineage apart from our own is extinct. e dates of the most recent remains of many latesurviving lineages coincide with evidence that our own lineage had turned up in their habitats. is uncanny coincidence of events also has a simple interpretation: our ancestors killed o all the other human lineages in Africa, left Africa for Europe where they killed o the Neanderthals, and then spread across the rest of the world killing o whatever remnant populations of nonsapiens human they encountered. is was essentially the big picture of relatively recent human evolution when the eld of ancient DNA was rst established. Given our species’ selfish tendencies, it’s not surprising that Neanderthals and early Homo sapiens were among the rst targets for ancient DNA research. What these early studies found, however, surprised everyone. e rst Neanderthal DNA sequence was published in 1997. is study, like most genetic research that focuses on Neanderthals, was led by Svante Pääbo, who at the time was a professor at the University of Munich but is now director of the department of genetics at the Max Planck Institute for Evolutionary Anthropology in Leipzig.

In 1997, Pääbo and colleagues published the sequence of a small fragment of Neanderthal mitochondrial DNA. Mitochondrial DNA was a common target of early ancient DNA studies for a few reasons. First, every cell has thousands of copies of the mitochondrial genome (mitochondria are organelles found outside the cell’s nucleus and have their own genomes) but only two copies of the nuclear genome. is means that mitochondrial DNA is simply more likely than nuclear DNA to survive in fossils.

Second, mitochondria are passed down the maternal line, which makes their evolutionary history simple to interpret. e mitochondrial DNA that Pääbo published in 1997 was distinct from all mitochondria present in modern humans, which suggested (like the fossil record) that Neanderthals and humans evolved along separate paths.

In the early 2000s, new approaches to sequencing DNA made it economical and practical to try to sequence a Neanderthal nuclear genome. In 2010, Ed Green, Svante Pääbo, and others collaborated to produce a complete draft sequence of the Neanderthal genome and, for the rst but certainly not last time, ancient DNA rewrote human evolutionary history. With this rst draft genome, the team con rmed that Neanderthal populations and modern human populations separated around 460,000 years ago, approximately when the fossil record suggests that the earliest hominins with typical Neanderthal morphologies appeared in Europe.

However, the data also delivered a surprise. Some fragments of what could now be identi ed as Neanderthal DNA were present in modern human genomes. is could only be explained if our cleanly branching evolutionary tree were not cleanly branching after all—if the lineages leading to Neanderthals and modern humans had rst separated and then, later, come back together again.