Is it really healthier to live in the countryside?

But evidence-based research that can help us identify the healthiest environments to live is surprisingly scant. As scientists begin to tease apart the links between well-being and the environment, they are finding that many nuances contribute to and detract from the benefits offered by a certain environment – whether it be a metropolis of millions or a deserted beach.

“What we’re trying to do as a group of researchers around the world is not to promote these things willy-nilly, but to find pro and con evidence on how natural environments – and our increasing detachment from them – might be affecting health and well-being,” says Mathew White, an environmental psychologist at the University of Exeter Medical School.

White and other researchers are revealing that a seemingly countless number of factors determine how our surroundings influence us. These can include a person’s background and life circumstances, the quality and duration of exposure and the activities performed in it.

Generally speaking, evidence suggests that green spaces are good for those of us who live in urban areas. Those who reside near parks or trees tend to enjoy lower levels of ambient air pollution, reduced manmade noise pollution and more cooling effects (something that will become increasingly useful as the planet warms).

Wellington, New Zealand

The research shows that green spaces are good for urban dwellers, which should be welcome news to residents of Wellington, New Zealand (Credit: Getty Images)

Natural spaces are conducive to physical and social activities – both of which are associated with myriad benefits of their own.

Time in nature has been linked to reduced physical markers of stress. When we are out for a stroll or just sitting beneath the trees, our heart rate and blood pressure both tend to go down. We also release more natural ‘killer cells’: lymphocytes that roam throughout the body, hunting down cancerous and virus-infected cells.

Researchers are still trying to determine why this is so, although they do have a number of hypotheses. “One predominate theory is that natural spaces act as a calming backdrop to the busy stimuli of the city,” says Amber Pearson, a health geographer at Michigan State University. “From an evolutionary perspective, we also associate natural things as key resources for survival, so we favour them.”

This does not necessarily mean that urban denizens should all move to the countryside, however.

City residents tend to suffer from more asthma, allergies and depression – but they also tend to be less obese, at a lower suicide risk and are less likely to get killed in an accident

City residents tend to suffer from higher levels of asthmaallergies and depression. But they also tend to be less obese, at a lower risk of suicide and are less likely to get killed in an accident. They lead happier lives as seniors and live longerin general. (Read more aboutfive of the world’s healthiest cities).

City-dwellers live longer than their countryside counterparts and are happier as seniors

City-dwellers live longer than their countryside counterparts and are happier as seniors (Credit: Getty Images)

Although we tend to associate cities with pollution, crime and stress, living in rural locales may entail certain costs as well. Disease-carrying insects and arachnids can detract from the health factor of that otherwise idyllic cabin in Maine, for example.

In other cases, rural pollution poses a major threat. In India, air pollution contributed to the deaths of 1.1 million citizens in 2015 – with rural residents rather than urban ones accounting for 75% of the victims. This is primarily because countryside dwellers are at greater risk of breathing air that is polluted by burning of agricultural fields, wood or cow dung (used for cooking fuel and heat).

Indonesia’s slash and burn-style land clearing likewise causes a blanket of toxic haze that lasts for months and sometimes affects neighbouring countries, including Singapore, Malaysia and Thailand. Meanwhile, smoke pollution from fires lit in South America and southern Africa has been known to make its way around the entire southern hemisphere. (That said, the air in the southern hemisphere is generally cleaner than in the northern hemisphere – simply because there are fewer people living there).

Pollution can kill more people in the countryside than the cities

Because of practices like agricultural clearing, pollution can kill more people in the countryside than even in cities (Credit: Getty Images)

It’s not just developing countries, either: wildfires in the western US are wreaking havoc on air quality, while pollution from fertilizers used on farms are detracting from air quality in Europe, Russia, China and the US.

What about the idea of that pure mountain air? It’s true that black carbon aerosols and particulate matter pollution tends to be lower at higher altitudes. But trying to move above air pollution may cause other issues.

While people who live in in places 2,500m or higher seem to have lower mortality from cardiovascular disease, stroke and some types of cancers, data indicate that they also seem to be at an elevated risk of death from chronic pulmonary disease and from lower respiratory tract infections. This is likely at least in part because cars and other vehicles operate less efficiently at higher altitudes, emitting greater amounts of hydrocarbons and carbon monoxide – which is made even more harmful by the increased solar radiation in such places. Living at a moderate altitude of 1,500 to 2,500 meters, therefore, may be the healthiest choice.

It’s not always true that the higher the altitude, the healthier the place

It’s not always true that the higher the altitude, the healthier the place (Credit: Getty Images)

There is a strong argument to be made for living near the sea – or at least near some body of water

On the other hand, there is a strong argument to be made for living near the sea – or at least near some body of water. Those in the UK who live closer to the ocean, for example, tend to have a better bill of health than those who live inland, taking into account their age and socioeconomic status. This is likely due to a variety of reasons, White says, including the fact that our evolution means we are attracted to the high levels of biodiversity found there (in the past, this would have been a helpful indicator of food sources) and that beaches offer opportunities for daily exercise and vitamin D.

Then there are the psychological benefits. A 2016 study Pearson and her colleagues conducted in Wellington, New Zealand found that residents with ocean views had lower levels of psychological distress. For every 10% increase in how much blue space people could see, the researchers found a one-third point reduction in the population’s average Kessler Psychological Distress Scale (used to predict anxiety and mood disorders), independent of socioeconomic status. Given that finding, Pearson says, “One might expect that a 20 to 30% increase in blue space visibility could shift someone from moderate distress into a lower category.” Pearson found similar results in a follow-up study conducted near the Great Lakes in the US (currently in review), as did White in an upcoming study of Hong Kong residents.

The more ‘blue space’ people saw in their everyday life, the less distress and anxiety

Researchers found that the more ‘blue space’ people saw in their everyday life, the less distress and anxiety they experienced (Credit: Getty Images)

Not everyone can live on the coast, however. So Simon Bell, chair of landscape architecture at the Estonian University of Life Sciences and associate director of the OPENspace Centre at the University of Edinburgh, and his colleagues are testing whether restoring neglected bodies of water throughout Europe can help. They are interviewing residents before and after restoration, including at a rundown beach outside of Tallinn, Estonia and an industrial canal near a Soviet bloc-style apartment complex in Tartu, also Estonia, among other places in Spain, Portugal, Sweden and the UK.

The team’s second analysis of nearly 200 recently redeveloped water sites will allow them to tease out how factors such as climate, weather, pollution levels, smells, seasonality, safety and security, accessibility and more, influence a given water body’s appeal. The ultimate goal, Bell says, is to find “what makes a great blue space.” Once the results are in, he and his colleagues will develop a quality assessment tool for those looking to most effectively restore urban canals, overgrown lakes, former docklands, rivers and other neglected blue spaces to make residents’ lives better.

How much we benefit from even a single visit to the coast depends on a variety of factors

How much we benefit from even a single visit to the coast depends on a variety of factors (Credit: Getty Images)

Still, when it comes to wellbeing, researchers do not know how lakes compare to oceans or how rivers compare to seas. Nor have they compared how beaches in, say, Iceland measure up to those in Florida. What they do know is that complex factors including air and water quality, crowding, temperature and even high and low tides affect how something as seemingly simple as a visit to the beach can influence us.

“There might be a million other important things besides weather and daylight that influence someone in Hawaii versus Finland,” White says.

People who live in less regularly sunny places, like Vermont or Denmark, tend to have higher rates of skin cancer

In terms of health, data also suggest that, counterintuitively, people who live in more intermittently rather than regularly sunny places – Vermont and Minnesota in the US, for example, and Denmark and France – tend to have higher rates of skin cancer, likely because sunscreen is not part of daily routines. (Read more aboutfive countries where people live the longest).

Just as some green and blue spaces may be more beneficial than others, researchers are also coming to realize that the environment’s influence on well-being is not evenly distributed.

People living in lower socioeconomic conditions tend to derive more benefits from natural spaces than wealthy residents, White says. That’s likely because richer people enjoy other health-improving privileges, such as taking holidays and leading generally less stressful lives – a finding with important real-world implications. “Here in the UK, local authorities have a legal obligation to reduce health inequalities. So one way to do that is to improve the park system,” White says. “The poorest will benefit the most.”

A clean, oceanside city like Sydney may be one of the best options

A clean, oceanside city like Sydney may be one of the best options (Credit: Getty Images)

It’s also important to point out that simply moving to a relatively pristine coast or forest will not solve all of our problems. Other life circumstances – losing or gaining a job, marrying or divorcing – have a much greater impact on our health. As White puts it, no matter what environment you’re in, “It’s more important to have a house than to be homeless in a park.”

Bell adds that proximity to nature actually tends to rank low on people’s lists of the most important factors for selecting a place to live, after things like safety, quietness and closeness to key locations like schools and work. But while the benefits of green and blue spaces should not be overplayed on an individual level, they are important for the scale at which they work.

And even so, one takeaway seems obvious: those living in a clean, oceanside city with ready access to nature – think Sydney or Wellington – may have struck the jackpot in terms of the healthiest places to live.

By Rachel Nuwer 1 June 2018

Advertisements

15 Tiny Things That Could Seriously Improve Your Life In Just A Month

1. If a task if going to take you less than a minute to complete, do it as soon as you think of it.

The One-Minute Rule is simple, but it works! Getting out of the habit of putting things off is the easiest way to get shit done.

2. Read for a set amount of time every single day.

Even if it’s 10 or 20 minutes, you’ll either finish or make good progress on a book by the end of the month.

@empowerpuffgurl / Via instagram.com

3. Actually start flossing your teeth at least once a day.

It will be worth it when you don’t have to lie at your next dentist appointment.

4. Try and go to bed at the same time each night, and wake up at a similar time each morning.

Your body loves habits, especially good sleep habits. Set a go-to-bed alarm, as well as a wake-up alarm, and try and stick to both most days.

5. Make your bed each and every morning.

Coming home to a bedroom with a made bed is a pure delight. Once you’re in the habit of making your bed, you won’t be able to believe you ever left the house without doing it.

@inbedstore / Via instagram.com

6. Add one new healthy food or ingredient into your diet.

Adding something healthy feels way better than taking something out of your diet, so choose a new vegetable, grain, or spice and work it into your meal rotation.

7. Find a workout you can do comfortably in your own home, and do it regularly.

Even if it’s just a short routine of push-ups, sit-ups, lunges, and squats, you’ll always have something to do on days you can’t be bothered getting to the gym or a class.

8. Instead of putting things down, put them away.

Leaving things where they don’t belong is how homes get messy. Avoid an hour of tidying up by taking a few seconds to put things away as you finish with them.

@mojkkaa / Via instagram.com

9. Each night, plan what you’re going to wear the next day.

If you find mornings a struggle, try preparing your outfit for the next day, the night before.

10. Practice a new skill or hobby for 10 minutes every day.

Whether it’s watercolor painting, embroidery, violin, or learning a new language, dedicating10 minutes a day to it guarantees you’ll have improved by the end of the month.

@threadhoney / Via instagram.com

11. Save every $5 bill that makes its way into your wallet.

A lot of people swear by this simple money-saving trick. Stash away every $5 note you come across, and enjoy your savings at a later date.

12. Write down three things you’re grateful for each night before bed.

Keeping a gratitude list or journal is a lovely practice that helps highlight all the good things you have going on in your life.

@bujocute / Via instagram.com

13. Try meditating, starting with just three minutes a day.

The first session on the Calm app is just three minutes long. Start there, and see how you feel after a month of daily meditation.

14. Keep track of how much water you’re drinking, and set daily hydration goals.

Most of us aren’t drinking enough water, so keeping a tally of how many glasses you’re having a day is a good way to see if you need to improve your habit.

@rockonrubyxx / Via instagram.com

15. Call someone when you’re having a bad day, whether that person is a friend, family member, or health professional.

Find your person, then get into the habit of calling them to chat more regularly.

@sarachengrocks / Via instagram.com
Gyan Yankovich

An Australian railway man saved more than 2 million babies—including his own grandchild—with a simple donation of blood

Featured image
James Harrison. Photo by: Australian Red Cross

An Australian man who required blood transfusions to survive surgery as a teenager decided to repay the kindness of strangers by becoming a blood donor himself. Little did he know at the time that his blood contained a rare antibody required for a life-saving medication. By the time he retired from donating this month, James Harrison had saved an amazing estimate of 2.4 million babies!

James Harrison came to blood donation from personal experience. When he was 14 years old, he underwent major lung surgery that took hours and required a vast quantity of transfusions—13 units of blood, in fact. He remained hospitalized for three months. So he decided to pay it forward as soon as he could. In Australia, blood donors must be a minimum of 18 years old; so in 1954, when he turned 18, Harrison gave his first units of blood. Despite a fear of needles, he returned to donate every few weeks for a remarkable 60 years.

But the Good Samaritan’s good deed turned out to be more beneficial than he ever could have imagined. In the 1960s, researchers discovered that Harrison’s blood contained a rare antibody used in a medication called Anti-D that helps save babies from a potentially fatal disease. The Australian Red Cross reports that Harrison’s blood has been used in more than 3 million doses of Anti-D since 1967, and that he has helped save the lives of 2.4 million babies, including that of his grandchildren. His daughter, Tracey Mellowship, received the injection and had two healthy babies. The Red Cross called him “the man with the golden arm.”

The Anti-D injections are given to pregnant Rh(D) negative women carrying Rh(D) positive babies, whose blood-type incompatibility can result in miscarriage, brain damage, or even stillbirth, according to the Australian Red Cross. Around 17 percent of Australian women need the injections, which come only from blood plasma from a “tiny pool” of around 160 donors who have the rare antibody that Harrison has. Attempts to make a synthetic version of the medication have so far failed.

Harrison had been donating for a decade when researchers discovered his blood was perfect for their new Anti-D program.

A Man Saved A Condor Years Ago And The Bird Still Flies Back To Say Thanks

On May 11, Harrison, now 81 and retired from his job as a railway administrator, lay back and had his arm strapped and swabbed as he got ready to give his last donation. As always, he looked away from the needle, and gripped a stress ball in his other hand. Medical officials with the Red Cross said it was time for Harrison to retire and save his blood for his own health. He received the Medal of the Order of Australia in 1999 for his service to the Anti-D program. He also made it into the Guinness Book of World Records in 2003.

Harrison’s last donation at the Town Hall Blood Donor Center in Sydney was videotaped and shown on the local TV news. (Harrison, ever the proper railway man, wore a tie to the occasion.) Helium balloons above his head had the numbers 1, 1, 7, and 3 to represent the 1,173 times he had donated blood. A half-dozen moms who had benefited from the Anti-D injection program showed up, their babies in their arms, to commemorate the unassuming hero.

“The end of an era,” Harrison, who lives in New South Wales, told the New York Times. “It was sad because I felt like I could keep going.”

Harrison was proud of having helped though not unduly vain about his accomplishment. He hopes the publicity surrounding his retirement will inspire other blood donors to come forward; perhaps one will also carry the rare antibody.  “Saving one baby is good,” Harrison told the New York Times. “Saving two million is hard to get your head around, but if they claim that’s what it is, I’m glad to have done it.”

 E.L. Hamilton

In fifth-century Europe, socks were usually worn by “holy” people to symbolize purity

Featured image
The earliest known surviving pair of socks Author: David Jackson  CC BY-SA 2.0

Although nowadays socks seem to be nothing more than just a simple detail of one’s outfit, the fact is that they have come a long way and dramatically evolved over the centuries. Socks are considered by many as being the oldest type of clothing to have ever existed, dating back to the Stone Age when our ancestors first started using animal skin for the purpose of covering their feet and ankles in order to provide much-needed warmth and comfort.

The oldest known surviving pair of socks was discovered in the city of Oxyrhynchus, Egypt. They date back to 300-500 A.D. and were created by needle-binding. Today, these strange looking ancient socks are on display at the Victoria and Albert Museum in London. The museum explains that:

“The Romano-Egyptian socks were excavated in the burial grounds of ancient Oxyrhynchus, a Greek colony on the Nile in central Egypt at the end of the 19th century. They were given to the Museum in 1900 by Robert Taylor Esq., ‘Kytes,’ Watford. He was the executor of the estate of the late Major Myers and these items were selected among others from a list of textiles as ‘a large number of advantageous examples.”

It appears that humans have embraced the benefits of wearing socks since the earliest cultures and civilizations, including people of Ancient Greece. The famed Greek poet, Hesiod, gives us one of the first written accounts of the importance of keeping our feet warm by using “piloi,” ancient type of socks made from matted animal hair.

 In his didactic poem entitled Works and Days, Hesiod advises his brother Perses to protect himself by using this particular type of ancient socks: “Around your feet, tie your sandals made from brutally hunted oxen skin and, under these, dress them in piloi.” 

They came, they saw, they wore socks with sandals. As you might have already guessed, we are talking about the Ancient Romans. Several years ago, an archaeological dig in North Yorkshire brought archaeologists to a conclusion that Roman legionnaires wore socks with sandals. Although one can rarely see an Ancient Roman sculpture that features socks, the fact is that Ancient Romans, similarly to the Ancient Greeks, also wore socks for protection against cold weather.

While Ancient Greeks and Romans used socks for functional purposes, among Europeans of the 5th century A.D., socks become known as puttees and were usually worn only by “holy” people to symbolize purity.

Status symbols, both financial and cultural, have existed for quite a long time throughout our history with every era being defined by a different one. We all know the status symbols of our own era, but one might be surprised to find out that around 1,000 years ago a rather strange object was considered a mark of social standing, and that was, believe it or not, a pair of colored socks.

It was not until 1000 A.D. that socks became a prominent object in everyday life and a symbol of wealth among the nobility. However, this changed with the invention of the knitting machine in 1589, which made it possible for socks to be knitted far faster than knitting them by hand as people did before. A strange new substance known as nylon was introduced in 1938 which caused a revolution in the entire textile industry and changed sock production forever.

 

Today in the 21st century, socks can be found for any kind of need, purpose, or style; the only thing that remains a struggle is to keep one pair of socks complete.

 Alex .A

Crinolinemania: This deadly Victorian fashion garment killed around 3,000 women

Featured image

Observed from today’s perspective, crinolines look utterly uncomfortable and unattractive to the point of absurdity. Why would anyone want to wear something that resembles a gigantic whipped-cream cake around their waist? Yet fashion trends have shown that comfort and attractiveness often have little in common, so it can be said that crinolines were just what any fad is–a way to get all eyes on you even if the cost is being a real (fashion) victim.

One of the fashion trends of the 19th century Victorian Era that stirred lady fashionistas was the so-called “Crinolinemania,” a craze that referred to the fashion obsession with the crinoline, a stiffened underskirt made using horsehair and linen or cotton, invented in the early 1840s.

These skirts were the followers of the “panniers” women’s underwear worn in the 17th and 18th centuries that enabled extending of the skirt at the side, thus creating a large side-squared dress that properly displayed the garment’s decorations.

Comic photograph, c.1860.

However, according to some fashion historians, the real predecessor of the crinoline was the 16th-century Spanish “farthingale.” These wide, full skirts were much adored by the Spanish ladies even back in the 15th century. The queen consort of Castile, Joana of Portugal, copied their style and introduced it to court, attracting admiring attention, although court rumor had it that the main reason she wore the style was to hide her illegitimate pregnancy. England became acquainted with the crinoline when Catherine of Aragon, first wife of Henry VIII, wore a Spanish farthingale made of linen and cane sticks.

In the first half of the 1800s, skirts became bigger and adopted a round shape. The ladies created an illusion of a large circle at the bottom part of their attire by wearing numerous layers of petticoats. This layered clothing often disabled the ladies’ movement and comfort, so when the crinoline was finally invented, they felt a relief. Crinolines weighed less and fit more easily to the body.

The name of the fashion fad first appeared in the 1800s in the magazine Punch, which mocked the crinoline craze and published humorous cartoon illustrations about Crinolinemania. The root of the garment’s nickname originates in the French words crin (horsehair) and lin (linen), which describe the materials of which the initial versions of the crinoline were made. The horsehair crinolines supported the weight of the layers of petticoats under the full skirts and provided more convenience.

Inflatable crinolines. Caricature, Punch, January 1857.

One of the most widely known models is the cage crinoline which was first patented in 1856 by R.C. Milliet in Paris. His agent brought it to Britain and it became popular overnight. These crinolines were made of spring steel with lightness providing flexibility and enabled women to walk and sit while wearing them.

Cage crinoline underskirt, the 1860s, MoMu.

 The ladies felt liberated in comparison to their previous layered petticoats and praised their experience in the Lady’s Newspaper in 1863: “So perfect are the wave-like bands that a lady may ascend a steep stair, lean against a table, throw herself into an armchair, pass to her stall at the opera, and occupy a further seat in a carriage, without inconveniencing herself or others, and provoking the rude remarks of observers thus modifying in an important degree, all those peculiarities tending to destroy the modesty of Englishwomen; and lastly, it allows the dress to fall in graceful folds.”

These positive reviews stimulated a massive production of crinolines led by the most successful producer, Douglas & Sherwood’s Hoop Skirt Factory in New York. The mass-production made crinolines affordable to women who stood at different levels on the social ladder. On daily occasions, most of the women wore small crinoline versions while the large bell-shaped models, some up to six feet in diameter, were worn on special occasions such as balls.

Three women showing dresses in blue with black lace and white with red stripes and brown color with queue de Paris

Nevertheless, due to their heaviness and robustness, crinolines had disadvantages that completely outweigh the advantages. Wearing them in the summer meant spending the day in hot, unhygienic conditions. The biggest issue, however, was a fatal one.

The enormous size of the crinolines was often too challenging for the women in specific surroundings, and thus there were thousands of reported cases of ladies being severely injured or burned alive when a candle or a spark from the fireplace would accidentally flame by touching the crinoline. Sometimes the hoops would also get caught in machinery or be run over by carriage wheels, causing serious consequences to the wearer.

 Brad Smithfield

Darwinian medicine

Darwinian medicine, field of study that applies the principles of evolutionary biology to problems in medicine and public healthEvolutionary medicine is a nearly synonymous but less-specific designation. Both Darwinian medicine and evolutionary medicine use evolutionary biology to better understand, prevent, and treat human disease. These goals are very different from concerns about the human species pursued under the rubric medical Darwinism in the late 19th and early 20th centuries.

Darwinian medicine, which is named for English naturalist Charles Darwin, whose theory of evolution by natural selectionbecame the foundation of modern evolutionary studies, is not a method of practice or a specialized area of research. Like embryology, evolution provides a basic science foundation for all research and clinical practice. Some applications are very practical, such as using evolutionary modeling to understand antibiotic resistance or the reasons why disease-causing genespersist. Other applications are more fundamental. For example, an evolutionary foundation deepens scientists’ understanding of what disease is, and it explains why the metaphor of the body as a designed machine is inadequate.

Evolutionary applications in medicine are diverse, ranging from established methods such as population genetics to newer attempts to understand why the body has traits, such as the narrow birth canal in females, that leave it vulnerable to disease. Evolutionary explanations can be based on the phylogeny (evolutionary history) of the trait or on its proposed adaptive significance. They can address five kinds of traits acted on by evolution (human traits, human genes, pathogen traits, pathogen genes, and cell lines). The intersection of these two kinds of explanations with five objects of explanation defines 10 areas of work in the field.

Established Applications

Much of Darwinian medicine consists of well-established applications of evolution to medicine. For instance, population genetics is intrinsically based on evolutionary biology, phylogenetic methods have long been useful in medicine, and antibiotic resistance is recognized as an example of natural selection. New methods and data have expanded these applications. In genetics, for example, methods have been developed to identify chromosome locations subjected to strong recent selection, such as locations near the lactase gene that influence whether adults can digest milk. Modern phylogenetic methods use genetic data for diverse tasks, from tracing the specific source of an infection to tracing the genetic heritage of an individual. Informal evolutionary thinking about antibiotic resistance has been replaced by rigorous mathematical models that have major implicationsfor public health.

Developing Applications

Other applications of evolutionary biology to medicine are still developing. In particular, studies to test hypotheses about why natural selection has left the human body vulnerable to disease expanded after 1991, when an article titled “The Dawn of Darwinian medicine,” published in The Quarterly Review of Biology and written by American evolutionary biologist George Williams and physician Randolph Nesse, argued that evolutionary explanations are needed to explain not only why bodies usually work well but also why they have aspects that leave them vulnerable to disease. The major evolutionary reasons that explain why bodies remain vulnerable to disease can be organized into six categories. Mismatches between the environments that humans evolved in and that they now occupy account for the prevalence of substance abuse, obesityhigh blood pressureatherosclerosis, and breast cancer. A second reason for vulnerability is the speed with which infectious organisms evolve ways to deal with antibiotics and the protective defenses of the human body. This process of coevolution results not in benign coexistence but in levels of virulence (ability to damage tissues) shaped to maximize the rate of pathogen spread. Virulence often depends on the route of transmission. For instance, respiratory viruses severe enough to keep victims in bed are likely to be displaced by less-severe strains whose victims are mobile enough to infect others. In contrast, malaria parasites spread faster when they make the host too sick to defend against mosquitoes; thus, malaria tends to be quite virulent.

Vulnerability results also from constraints. For example, the eyes of vertebrates are poorly designed, with a blind spot, and nerves and vessels run between the point where light enters the eye and the retina. The octopus eye, by contrast, has no blind spot. Another constraint is the inevitability of DNAreplication errors. Bodies are also subject to engineering constraints and trade-offs. Bones could be thicker, but bodies would then be heavier and slower. Darwinian medicine emphasizes that nothing in the body can be perfect, since every trait is subject to constraints and trade-offs.

Selection shapes bodies for maximum reproduction rather than health. Usually optimal health and reproduction coincide, but mutations that increase reproduction tend to spread, even if they decrease health and longevity. Higher male than female mortality rates in polygynous species (species that have more than one mate) are an example. In such species an incremental investment in bodily protection and repair increases reproductive fitness more for females than for males.

Additionally, many symptoms are not diseases but protective responses shaped by natural selection. Painfever, cough, and anxiety are aversive and useful responses. Nonetheless, medications can often safely block their expression, because of the “smoke-detector principle.” Humans put up with sensitive smoke detectors set off by making toast because such false alarms are a minor nuisance compared with the huge cost of not being alerted to a fire. Likewise, the cost of many bodily defenses is low compared with the cost of not expressing a defense when it is needed, so the normal mechanisms shaped by natural selection give rise to many false alarms and apparently excessive responses.

Practical Implications

Darwinian medicine has narrowed the gap between evolutionary biology and medicine and contributed to improvements in the understanding of health and disease. Some advances have been straightforward, such as new public health policies based on formal evolutionary models of antibiotic resistance and evolutionarily informed searches for genes that cause disease. Other advances have come from asking new evolutionary questions about why natural selection has left bodies vulnerable to disease. Applications of these advances are less direct, but they may be more fundamental. They encourage new studies of phenomena with enormous clinical importance, such as why males die younger than females and how selection shapes mechanisms that regulate protective responses such as pain and fever. They offer a more fully biological view of the body and disease

Written by Randolph M. Nesse