Artist’s impression of Stenopterygius quadriscissus, an ichthyosaur
dotted zebra / Alamy Stock Photo
PREHISTORIC Earth was a place of monsters. There were 2.5-metre-long millipedes, flying reptiles with 11-metre wingspans and snakes that weighed over a tonne. But if it is the biggest animal of all time you are looking for, conventional wisdom says you don’t need to step back in time. The blue whale is known to reach 30 metres in length and to weigh 199 tonnes. Nothing else in more than half a billion years of animal evolution comes close, not even the largest dinosaur.
Conventional wisdom might be wrong. The fossil record may be concealing an animal that was even bigger than a blue whale. For decades there has been a slow trickle of evidence that a truly enormous super-predator swam the seas between 200 and 250 million years ago. Now, a string of discoveries and reanalysis of previous findings has dramatically bolstered the case.
The implications are far-reaching. We don’t know exactly what this huge animal looked like and it doesn’t even have a name. We have, however, begun to work out how such a gigantic creature could feed itself in the prehistoric seas. Confirmation that it outgrew the blue whale would tell us that we may have drastically underestimated how large toothed carnivores can grow. More than that, the discovery that such leviathans appeared shortly after the most devastating mass extinction in Earth’s history suggests we may need to rethink the factors that drive evolution on such an epic scale.
When dinosaurs ruled the land, several groups of marine reptiles dominated…
I HAVE seen my future and it is full of beans, both literally and metaphorically. As well as upping my bean count, there will be a lot of vegetables, no meat, long periods of hunger and hardly any alcohol. But in return for this dietary discipline, my future will also be significantly longer and sprightlier. I am 52 and, on my current diet, can expect to live another 29 years. But if I change now, I could gain an extra decade and live in good health into my 90s.
This “longevity diet” isn’t just the latest fad, it is the product of more than a human lifespan of scientific research. And it isn’t merely designed to prevent illness, but to actually slow down the ageing process – that’s the claim, anyway.
Of course, it is a no-brainer to say that our diets can alter our lifespans. Worldwide, millions of people still die prematurely every year from lack of calories and nutrients. Meanwhile, an estimated 11 million die each year from too many calories and the wrong sort of nutrients. Scoffing more than we need inevitably leads to obesity and its pall-bearers, cardiovascular disease, diabetes and cancer. Typical Western diets are also high in sugars, refined starches and saturated fats and low in wholefoods, which add insult to injury by disrupting metabolism. That includes the excessive release of insulin, the hormone that keeps blood sugar levels under control and has a direct impact on ageing. Suffice to say that Western diets don’t push the longevity lever in the right direction. But is it really possible to eat oneself into a later grave?…
Article amended on 29 June 2022
We have corrected step 5 of the longevity diet.
Article amended on 20 July 2022
We corrected the main target of amino-acid restriction.
COURTNEY SHUKIS was looking forward to lunch: she had just recovered from covid-19 and was glad to be meeting her friends again. Before leaving her home in Plano, Texas, she checked the calendar, making a mental note of the restaurant and when to meet. “But instead of going there, I got in my car and drove to a completely different place,” she recalls. “I sat at the table for half an hour, looking at my phone, wondering where everyone was. My brain fog was really bad.”
That wasn’t a one-off. After having covid-19, Shukis had frequent episodes of memory loss. She would forget to make dinner, had trouble finding the words to describe things and got confused about school pick-up times. “I had never had any difficulties with these kinds of things before. It just felt like my brain wasn’t working right.”
Shukis is one of millions of people worldwide reporting a severe dent in cognitive functioning following a covid-19 infection, and as a result, the issue of brain fog has been thrust into the limelight. For many, this is long overdue. “It’s something that patients with a wide variety of different medical problems have said has interfered with their ability to function for a long time,” says Sabina Brennan, a neuroscientist at Trinity College Dublin, Ireland, and author of Beating Brain Fog. The hope is that this interest could improve care for those experiencing it. “If there’s anything positive to come out of the covid-19 pandemic, it’s that the spotlight is now on brain fog and the scientific community is paying much more attention to it,” says Brennan.…
SCIENTIFIC revelations come from the unlikeliest of places. Like a rat, in a lab, doing a “downward dog” stretch.
According to the people who found a way to get rats to do yoga, these creatures benefit from a good stretch as much as we do. In the process, they are revealing the true significance of a body tissue that has been overlooked by science for centuries.
The 19th-century anatomist Erasmus Wilson called this tissue – now known as fascia – a natural bandage. In dissection, that is exactly what it looks like: sheets of white, fibrous connective tissue that are strong yet flexible and perfect for keeping muscles and organs in place. They are also sticky, gloopy and get in the way of looking at the muscles, bones and organs they cover. Which explains why, for years, anatomists cut this tissue off, chucked it away and thought little more about it.
Recently, though, researchers have begun to take a fresh look at fascia and are finding that it is anything but an inert wrapping. Instead, it is the site of biological activity that explains some of the links between lifestyle and health. It may even be a new type of sensory organ. “There appears to be more going on in the fascia than is commonly appreciated,” says Karl Lewis at Cornell University in Ithaca, New York.
We are now realising that a better understanding of this ubiquitous tissue is sorely needed. If we manage to figure it out, it has the potential to provide new ways to tackle many common yet hard-to-treat conditions, from immune dysfunction to chronic pain.
One difficulty with studying fascia is that there is disagreement about what it actually is. It comes under the umbrella of connective tissue, which, at its broadest definition includes not only tendons and ligaments, but also bone, skin and fat.
Most fascia researchers, however, understand it to be sheets of tissue made up of strong collagen fibres and more stretchy elastin fibres. In many places, these fibrous sheets are separated by “areolar” or “loose” fascia, a form that contains fewer fibres and with the gaps between fibres filled with a slimy substance that allows the surrounding layers to slide over each other. The main ingredients of this slippery soup are hyaluronic acid, for lubrication, and proteoglycans, molecules that provide cushioning. The fascia fibres and the soup are both secreted by specialised cells in the tissue – fibroblasts and the recently discovered fasciacytes.
Holding us together
If you were to cut into the body, you would find two obvious layers of this natural cling film: the superficial fascia, which sits directly under the skin, and the deep fascia, which wraps muscles and organs and connects them to each other. Some researchers, however, extend the definition to include the visceral fascia, which lines the body cavity and divides it into compartments for different organs, and also thin layers of connective tissue that line pretty much every part of the body. By this definition, fascia forms a network that pretty much holds us together (see “A body-wide network“).
Remarkably, until the early 2000s, no one had studied this common tissue in detail. Among the first to do so was Carla Stecco, an orthopaedic surgeon and anatomist at the University of Padova in Italy. She started studying fascia 20 years ago when her father, a physiotherapist called Luigi Stecco, invented a form of physical therapy called fascial manipulation, which he claimed could treat everything from headaches to muscle and joint pain. His system is now one of many physical therapies that hinge on the idea that fascia can become stiff, and that it can be “released” through massage.
The only problem was that there was no evidence for or against the idea that physically manipulating the body did anything specifically to the fascia, or that this would affect pain. And as Carla Stecco soon discovered, there wasn’t even a body of literature explaining, in detail, what fascia actually was. It wasn’t even known if it had nerves associated with it, she says.
Since then, she and others have shown that fascia is indeed rich in nerves, and that the information that these relay varies throughout the body. Superficial fascia contains nerves that specialise in sensing pressure, temperature and movement. Deep fascia is involved in proprioception, the body’s sense of its position in space, and nociception, the sensing of pain.
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Because of this sensory role, some researchers say that fascia should be considered a new organ, one that is specialised for communication about the body’s internal state. Robert Schleip at the Technical University of Munich in Germany recently estimated that an adult’s fascia contains approximately 250 million nerve endings, similar to, or slightly more than the skin. “It is beyond any doubt our richest sensory organ,” he says. Others are more cautious. “It’s plausible, but there is a strict definition for an organ to do with material organisation, cell types and function, so it sounds like it’s a candidate,” says Lewis. “But it’s early days for making that determination.”
Organ or not, there is evidence that deep fascia specialises in a different kind of message to other bodily tissues. Experiments in which healthy human volunteers had painful injections into their skin, muscles and fascia showed that while nerves in the skin and muscles produce focused, localised pain, the network of nerves in fascia is linked to a radiating pain, one that is more difficult to pinpoint. This kind of diffuse pain is a feature of several chronic pain disorders, including fibromyalgia, which some studies have linked to inflammation in the fascia. It is also a feature of post-exercise soreness, which has long been blamed on damage to the muscles, but which some researchers now think has more to do with injury or inflammation in the fascia.
The bad news for anyone with inflamed fascia is that if it continues for too long, the body responds by altering the composition of fascial nerves to become more sensitive to pain. In rats, the percentage of nociceptive fibres – pain receptors that respond to harmful stimuli – in the fascia increased from 4 per cent to 15 per cent following chronic inflammation of deep fascia in the lower back.
This could help to explain why lower back pain is so difficult to treat. Despite being one of the most common causes of work absence and overall movement restriction, 85 per cent of cases worldwide are classified as non-specific, meaning the exact cause can’t be established.
Given what we now know about nerves in the fascia, the thoracolumbar fascia, a diamond-shaped, multilayered structure in the lower back in which different layers connect to different muscle groups in the trunk, is starting to look like a good place to put the blame for this back pain. “The thoracolumbar fascia is like a big receptor that is able to feel the tension coming from the upper limbs, the spine and the abdomen,” says Stecco. The sensory neurons in the fascia may respond to this tension by registering it as pain.
Fascia is a connective tissue made up of fibres of the proteins collagen and elastin
Prof. P. Motta/Dept. Of Anatomy/University "La Sapienza", Rome/Science Photo Library
On top of nerve changes, inflammation in the loose, areolar fascia that is found between fascial layers can make matters worse. Helene Langevin at the US National Institutes of Health in Maryland used ultrasound imaging of the lower back to show that people with chronic lower back pain had thoracolumbar fascia that was 20 per cent stiffer than those without this pain.
This stiffness seemed to be explained by multiple layers of tissue becoming stuck together, stopping the loose layer from sliding. Her studies in pigs have backed this up, showing that even after an initial injury has healed, a lack of movement in the lower back can be enough to keep the fascia stiff and to cause adhesions, where two layers become physically linked by new collagen fibres. This, other studies suggest, restricts movement, not only in the fascia immediately surrounding the stiff spot, but also in connected regions nearby. In particularly severe cases, fascial layers can become stuck into one immobile block that runs from the superficial fascia to the deep fascia and into the muscle.
Injury and inflammation aside, there are many other reasons why fascia may become stiff. Schleip’s research hints that activation of the sympathetic nervous system, which is involved in the body’s fight-or-flight response, causes the fascia to contract by prompting the fibroblasts within it to transform into myofibroblasts, cells that are part of the inflammatory response to injury, often seen in joint-related problems such as frozen shoulder.
The details of how exactly fight-or-flight stress leads to stiffness are still being worked out, but Schleip says that adrenaline seems to increase the expression of an inflammatory substance called TGF-beta. This is then stored in the loose fascia in preparation for the next time the body is stressed. When this happens, fibroblasts “drink [TGF-beta] and they become myofibroblasts in a few hours”, he says. “And then they are four times as strong as before. They are contraction machines. So, adrenaline can make fascia stiffer.”
In fact, the list of things that affect fascial stiffness is getting longer all the time. “Oestrogen is able to create a fascia that is more elastic,” says Stecco. “The fascia is a very dynamic tissue that is able to answer to hormonal input, chemical input and mechanical input. Altogether, that defines if our fascia is elastic or rigid.”
On the plus side, this dynamic nature of fascia suggests that lifestyle changes could help to reverse problems related to it. One promising intervention under investigation is stretching. In samples of rat tissue, Langevin found that stretching causes changes to the fibroblasts that make up the matrix of the loose fascia. She says they expand several fold and become longer and flatter. “Stretching the tissue allows it to relax,” she adds.
Stretch it out
Other studies by Langevin with pigs showed that stretching the lower back for 5 minutes, twice a day, not only reduced the size of an area of inflammation, but also seemed to induce a series of anti-inflammatory chemical events from the fascia. This is a promising finding because chronic inflammation has been linked to pretty much every modern ailment going, from heart disease and diabetes to cancer and depression.
A team at Harvard Medical School is conducting a trial in people to find out if the same is true in humans. A pilot study completed in late 2021 showed that healthy volunteers who undertook an hour-long stretching session had altered levels of immune system molecules called cytokines, compared with those who didn’t stretch, suggesting that there is a regulation of inflammation after stretching.
Future studies will assess whether levels of resolvins, chemicals made by the body that turn off inflammation, also increased, as has been seen in rat and pig stretching studies. If so, stretching could prove useful for reducing cases of more widespread chronic inflammation, which can be triggered by long-term stress, obesity and bad diet.
As for physical therapies that focus on fascia release, such as massage, it is unclear whether they have the same cellular and anti-inflammatory effects as stretching seems to, or whether they simply make temporary changes to the fascia. It could be, for example, that manual therapies warm the tissues, which has been shown to make the fascia matrix less viscous, temporarily allowing the layers to slide more easily. Langevin sounds a note of caution, that until more is known about what happens during these therapies, it isn’t clear what, if anything, they do to the fascia, or anything else.
In order to turn fascia research into evidence-based treatments, this tissue will also have to overcome its image problem among scientists. This dates back to the 1940s and 50s, when medical researchers were paying little attention to the stuff, and it became central to an alternative approach to health invented by the late biochemist Ida Rolf. Her method, which she called structural integration, but which is better known as Rolfing, is a mixture of physical therapy and claims about alignment of bodily energy fields. Since then, fascia has become a buzz word in all kinds of alternative therapies.
Stecco, however, thinks that it is high time for the mainstream medical profession to start paying attention to this tissue. She would like fascia to be recognised as important to many areas of medicine, and as a window into our overall health. This, she says, would be “the true revolution of the fascia”.
A body-wide network
Our understanding of how fascia affects health (see main story) depends on where you draw the line between where it begins and ends in the body.
Some people think that as well as the distinct layers of this tissue found under the skin and surrounding muscles, the term should also cover the interstitium: the fluid-filled connective tissue that lines every organ, muscle fibre and blood vessel.
If that is correct, the fascia makes a whole-body network of fluid that could function both as a shock absorber and an immune network relevant to inflammatory disorders, scar formation and the spread of cancer.
The true nature of the interstitium only became apparent in 2018 when a study by Neil Thiese at the Icahn School of Medicine at Mount Sinai, New York, and his colleagues used a new microscopic technique to look at its structure in a living person undergoing a biopsy. In the past, it was only possible to see this tissue by removing it and squashing it on a microscope slide. When seen in living tissue, what had previously looked like a dense tangle of fibres actually had a sponge-like structure filled with fluid that drained into the lymphatic system, part of the body’s immune set-up.
The team suggested that physical movement may help keep this fluid healthy, whether due to the pumping of the heart, the movement of the digestive tract or physical movement of the body. “It seems that no such spaces are static,” says Thiese. This discovery opens up the possibility that the body is connected in ways that we are only beginning to understand and that movement is required to keep this tissue healthy.
OUR planet is like a bad cake in a cosmic baking contest. On inspection of the first slice, the judges might say its layering is quite neat. The crunchy crust sits on a solid-but-squidgy mantle, which wraps around a gooey outer core. But cut another slice and they will soon see that something has gone awry. Looming inside the neat layers are two giant, messy lumps.
These two blobs are colossal. They are the size of continents, covering almost a third of the boundary between the core and the mantle. We also know that they are hotter than their surroundings. But everything else about these blobs is mysterious, from what they are made of and where they came from to how they affect our planet today.
The quest to understand them has so far verged on the quixotic. Geologists and planetary scientists are pursuing it with vigour, however, because the blobs are likely to be guarding some serious secrets. We are scrambling to get a better picture of these shadowy underworld titans, not least how ancient they are.
That is important because if they turn out to be geologically youthful, it would suggest we are living through a special epoch. There must be something particularly strange going on down there, to produce such giant oddities. Whereas “if these things are truly ancient”, says Sujoy Mukhopadhyay at the University of California, Davis, “it tells us something about how our planet formed”. And they might even surprise us with an answer to a bigger question, one that goes beyond parochial concerns about our own planet.
Since the late 19th century, geologists have used vibrations called seismic waves, normally generated by earthquakes, to map the interior of our planet. These waves move slowly in less dense and rigid rock, but faster through more tightly packed matter. After studying their speed in countless rock types, geoscientists sent seismic waves through Earth to see the composition of its internal structure: a solid inner core, surrounded by a liquid outer core, which sloshes molten iron and nickel around to generate its magnetic field. On top of this is the mostly solid mantle, the bulk of Earth’s interior. Capping all this is the crust, an amalgam of rocks that have been erupted, broken up, squashed together and pulled apart. This is what you learned about at school.
Dr. Hiroki Ichikawa (http://dagik.org/misc/gst/index.html)
But what you may not know is that, in the 1980s, seismic waves hit on something odd: two giant clumps inside the planet’s mantle, making up about 8 per cent of the mantle’s volume. These lumps sit on top of the liquid core, one below the Pacific, one beneath Africa. As wide as ocean basins, they also seem to rise almost 1000 kilometres vertically, into the mantle. They are uneven and misshapen, like the waxy blobs of a lava lamp. But right from the get-go, the questions of what they are doing there, and how they got there, have confounded Earth scientists.
It is even hard to know what to call them. When seismic waves hit the blobs, they slow down. This earned them the name “large low-shear-velocity provinces”, a clumsy collection of words. “It’s not an acronym you can easily say,” says Paul Byrne, a planetary scientist at Washington University in St Louis, Missouri. Some call them superplumes. Byrne insists “blob is fine”.
Most of what we know about these blobs is through seismology, but seismology has its flaws. Temperature changes the density and rigidity of a rock, but so does its composition. “It’s really hard to tell the difference between the two,” says Harriet Lau, a geophysicist at the University of California, Berkeley. Most agree that the blobs are probably hotter than the surrounding mantle, but it is hard to tell if they are made of the same stuff, with lots of iron in them, or if they are packed with other minerals.
Rise and fall
The simplest explanation is that they are made of the same material as the mantle, and are just hotter. If so, their presence may be a result of the disintegration of Pangaea, Earth’s most recent supercontinent, which formed around 330 million years ago and started breaking up around 200 million years ago. Continents are part of the planet’s outer shell, made of crust and some upper material in the mantle. As Pangaea broke into tectonic jigsaw pieces, prominent subduction zones – deep wounds that allow one tectonic plate to descend beneath another – opened up. For the past 250 million years, defunct chunks of tectonic plates, called slabs, have been descending into the lower mantle. Since the insides of our planet are hotter, the blobs might simply be the warm spots on the core-mantle boundary that aren’t receiving any of this cooler falling material.
Then again, the simplest explanation isn’t always the correct one. There is also a chance these blobs aren’t just hotter, but are also made of different stuff to the rest of the mantle. If so, where they came from is a mystery. And the key to solving the mystery lies in their density, which determines what rises and falls, and gives clues about temperature and chemical composition. “Density is kind of the holy grail in this debate,” says Paula Koelemeijer, a seismologist at Royal Holloway, University of London.
Working separately, Lau and Koelemeijer have both been trying to figure how dense these blobs are. In 2017, using GPS sensors to measure tidal changes to the shape of the crust caused by the blobs, Lau and her colleagues estimated the blobs to be fairly dense. But that same year, Koelemeijer and her colleagues used a type of seismic wave sensitive to deep mantle structures, to study where the blobs sit in relation to the core. They were always elevated above the rest of the core, hinting that they were less dense than the surroundings.
The two approaches “were showing us conflicting results”, says Koelemeijer. To crack the case, the researchers decided to team up. Early results from their new work indicating that the blobs may be mostly light – perhaps bundles of hot, buoyant mantle plumes – but with dense plant-like roots. But until the results are published, they don’t want to speculate about what this could mean for the blobs’ origins.
Another important conundrum is the age of these blobs. Scientists examined lava spewed by oceanic volcanoes powered by the blobs (see “Shaping Earth”), finding odd chemistry. Some of this volcanic material seems like it “hasn’t ever erupted at the surface of the planet”, says Lau. This includes radioactive elements dating back to the first 50 to 100 million years of Earth’s life, stuff you won’t find in younger rocks. “That’s a very strong argument to say there’s something really ancient down there,” says Mukhopadhyay.
Strangely shaped entities inside Earth rise out of the crust and into the mantle
Dr. Hiroki Ichikawa (http://dagik.org/misc/gst/index.html)
If so, that would go against the idea that plate tectonics caused the blobs. Plate tectonics began at least 3 billion years ago, but we don’t know exactly when it started. If the blob matter is truly primordial, even older than the advent of plate tectonics, then where else could it have come from? One option is that this material crystallised deep within the molten soup that was the very young Earth, remaining there since.
A more intriguing suggestion, which has been gaining interest in recent years, is that the blobs come from elsewhere in the solar system.
Around 4.5 billion years ago, when Earth was just an infant, an object the size of Mars, known as Theia, is thought to have slammed into the planet. This giant impact sent molten matter screaming into orbit around our magma-covered world, material that coalesced to form the moon. This idea of how the moon formed has been around since the 1970s, and remains the leading hypothesis. In recent years, however, some have taken it further, wondering if Theia may also be the origin of the blobs. Segments of Theia’s corpse could have been preserved on the fringes of Earth’s core for the past 4.5 billion years.
If that’s right, it would solve the origins of the Earth blobs and settle the debate over how the moon formed in one fell swoop. Except that is a tricky thing to prove. For one, Theia has been destroyed, so we can’t take samples to compare with the lava created by the blobs’ mantle plumes. Another issue arises when trying to virtually reproduce the giant, primordial impact. Chemical analyses of lunar material scooped up during the Apollo era suggest that the moon is mostly made of Earth material, but simulations of the giant primordial impact create a moon mostly made from Theia. A recent study suggested you get something geologically closer to the real moon if Theia hit a magma-ocean-covered Earth, but it still isn’t a perfect replication of reality.
There are various ways we could yet get a better understanding. If Earth blobs truly are primordial, then ancient radioactive elements would give off a unique neutrino signature that, hypothetically, could be detected at the planet’s surface. But that would need the right sort of detectors placed at the perfect spots, and we aren’t there yet.
Most scientists hope to do more with the tools they already have – seismology, chief among them. Most seismometers, the devices that detect seismic waves, are on land, which makes up less than a third of Earth’s surface area. The oceans, on the other hand, are “one massive blind spot that global seismology is yet to really improve upon”, says Lau. Floating seismometers, or vast arrays of sea-floor seismometers that can peer into the planet in considerable detail, are starting to fix that. This sort of research is showing our pair of mystery objects “not as two massive blobs, necessarily”, says Koelemeijer, “but much patchier with more details.”
The plot thickened last year when Qian Yuan, a doctoral student at Arizona State University, presented intriguing new results at the Lunar and Planetary Science Conference, held online. According to a combination of his colleagues’ prior work and Yuan’s computer simulations, after Theia’s collision with our planet 4.5 billion years ago, much of the upper segment of Earth was liquefied, and Theia was largely obliterated. About 20 per cent of Theia’s mantle punched through to Earth’s lower mantle, a solid layer that for the most part didn’t join in with the sloshing molten world above. Yuan’s argument is that there, below that shield, Theia’s mantle shards remain, surviving to this very day.
That may sound far-fetched, but it would tally with the hints of primordial matter in some of the lava driven onto the planet’s surface by the blobs’ plumes. And there might be ways to test Yuan’s hypothesis.
According to Yuan, samples of the moon’s crust offer additional clues. A team of his colleagues has studied the chemistry of these rocks, and found that they suggest the lunar mantle – a stand-in for Theia’s mantle – has a preponderance of dense iron oxide. That suggests the blobs are denser than Earth’s mantle.
If so, that may explain why they still exist today: instead of being swept up by the mantle’s currents and blended into it, their high density let them sink to the base of the mantle and become stubbornly stuck there, to this day. Subducting plates may be influencing the location and composition of the blobs today, but perhaps Theia gave birth to them. That would have been a sight to behold, says Yuan. “It’s beyond my imagination.”
Shaping Earth
Two vast blobs of anomalous material in Earth’s mantle (see main story) are, geologically speaking, alive. This layer of our planet is populated by towering streaks of superheated material that rise to inflict prolonged, island-making, continent-tearing and occasionally climate-changing volcanism on the surface.
Plume-driven volcanism is unlike any other. It has created chains of islands like the Hawaiian archipelago, home to by far the largest volcanoes on the planet. It played a key role in the dismantling of supercontinents and the creation of ocean basins. And it even contributed to the chaos that unfolded 65 million years ago, unleashing climate-changing volcanic gases while the world reeled from a major asteroid impact.
Although some seem to stand alone, most of these entities, named mantle plumes, appear to sprout from the two blobs. But the way they do this is subject to debate. They might rise up as one continual fountain, or they could appear as many little blobs that together give the illusion of one continuous plume. For now, the main investigation is into where they came from. “Until we know what the blobs are, it seems a bit premature to attribute them to any causal mechanism,” says Paul Byrne at Washington University in St Louis, Missouri.
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YOU open a door and it hits you – a flare of warmth on your skin. You brace yourself to go inside, battling smoke and heat. Flames flicker around you as you make your way through a burning building. You find what you came for and escape. Outside, it is so cold you start to shiver, while your hands and feet go numb.
But then you remove your headset and it all stops. You just finished an incredibly realistic training exercise. None of those sensations were caused by changes in your surroundings, although they felt real. Instead, chemicals carefully selected to mimic different feelings were pumped onto your skin.
Such stimulants have long been useful for understanding touch, the most complex of all human senses. In the 1990s, studies of capsaicin, an extract of chilli peppers, and menthol, found in peppermint, helped us pin down how our bodies react to hot and cold conditions. Now, Jasmine Lu and her colleagues at the University of Chicago are using this knowledge to create chemically induced sensations, to make virtual environments astonishingly realistic.
In a technology dubbed chemical haptics, they have built a wearable device that, when placed on the skin, can cause the wearer to experience a range of sensations – hot or cold, numb or tingly – on demand. Its uses could include creating intensely realistic virtual worlds for gamers to explore or for training firefighters. But will we ever be able to fully replicate the experience of touching something real, and what might we lose if we can’t?…
FEW of life’s milestones are as unappealing and unceremonious as arrival in middle age. Our skin becomes noticeably looser, grey hairs more numerous and, of course, our clothes typically start to feel a bit tighter – especially around the waist.
The last of these is known as middle-aged spread, the commonly accepted idea that we start to pack on the pounds around the abdomen as we get older. This excess weight is said to be easy to put on and harder to shift than when we were younger, the thinking being that our once-perky metabolism gets sluggish with age. We can no longer get away with as much, and our efforts to ditch the belly with diet or exercise become a losing battle.
So far, so miserable. But then, last July, a study of over 6000 people around the world blew the idea out of the water. It showed that metabolism stays remarkably stable as we age, at least until our 60s. “The amount of calories you burn per day from age 20 to 60 remains about the same,” says Herman Pontzer at Duke University in North Carolina. “We’ve shown that you have much less control over metabolism than we thought.” The idea that your metabolism is just as active as you approach your 60s as it was in your 20s should be welcome news for anyone nearing middle age – usually defined as the period from 45 to 65 years of age – and facing the dreaded spread. But it leaves a burning question: if metabolism isn’t to blame, then what is? And what can be done?
Melting permafrost in Russia’s Yamal peninsula (pictured) has exposed nomadic reindeer herders (below) to anthrax
Elena Shchipkova/Alamy
IN NOVEMBER 2019, the US National Academies of Sciences, Engineering and Medicine held a workshop to discuss an emerging disease threat. Not covid-19: they were a couple of months too early for that. Instead, they were trying to figure out what to do about microorganisms trapped in glaciers, ice sheets and permafrost, which will be released as the world warms and the ice thaws.
Many of us have felt more than a little stressed over the past couple of years. For me, exhibit A is my teeth. A recent trip to the dentist confirmed that months of pandemic-induced jaw-clenching, product of the usual deadline stress amplified by the demands of two young children, had left four of them broken.
Crumbling teeth are small fry. Last year, the American Psychological Association found that two-thirds of people in the US reported feeling more stressed in the pandemic, and predicted “a mental health crisis that could yield serious health and social consequences for years to come”. Increased risk of diabetes, depression and cardiovascular disease and more are all associated with high stress levels. It’s enough to make you feel stressed just thinking about it.
Perhaps we just need to think about stress differently, though. That, at least, is the startling conclusion of researchers studying the mind-body connection. There are natural benefits to being stressed, they say, and if we change our “stress mindset”, we might be able to turn things around and make stress a positive influence on our lives. Fortunately, there are some simple hacks that will allow us to do this, and they bring with them the promise of better physical health, clearer thinking, increased mental toughness and greater productivity.
There is no denying that too much stress can harm both body and mind. It has been linked to all six of the main causes of death in the West: cancer, heart disease, liver disease, accidents, lung disease and suicide. It can weaken the immune system, leaving us more prone to infection and reducing…
Letters to the editor from the April 2021 issue of Scientific American
Credit:
Scientific American, April 2021
PERCOLATION INSPIRATION
It was an absolute delight to read about percolation theory in “The Math of Making Connections,” by Kelsey Houston-Edwards. Please feature more articles by this author and about mathematics as applied to science. I’m not a mathematician, yet I enjoy learning about theory and application. I love the expanse of disciplines you cover.
I am an African-American woman with a biology degree. I used to work as a research assistant in cancer research. That was until the racism that I consistently encountered wore me down, and I just didn’t want to ever work with scientists again. Although I am in another line of work, I haven’t lost my love of the sciences and mathematics. Your magazine provides me with the joy I used to feel but without the heartache.
TRACIE S. JOHNSON via e-mail
One approach to developing a theory of quantum gravity is called loop quantum gravity (LQG). It treats space as a discrete substance composed of individual spatial atoms, or nodes, at the Planck distance scale of 10−35 meter. They are connected to one another in a way that would seem to lend itself very well to percolation theory, which is precisely geared toward modeling the connections among discrete nodes. Has percolation been applied to advancing LQG and quantum gravity?
EDWARD ROSENBLATT via e-mail
HOUSTON-EDWARDS REPLIES: In response to Rosenblatt: In percolation theory, a “dial” controls the local connectivity of a network. When its needle lands on a critical point, a phase transition occurs, and the global connectivity of the network changes dramatically. To apply the theory to LQG, one needs to describe how and why this dial moves to the critical point. But as theoretical physicist Lee Smolin explained in an e-mail to Scientific American, nature exhibits several instances of “self-organized critical phenomena,” in which the dial tunes itself toward the critical threshold. Smolin hypothesizes that such a self-organized phase transition might explain “the emergence of classical spacetime in a quantum theory of gravity,” including loop quantum gravity. He and physicist Mohammad Ansari explored these ideas in the 2008 paper “Self-Organized Criticality in Quantum Gravity.” It is unclear how extensively a “self-tuning” version of percolation could be used for understanding a self-organized phase transition in the case of LQG.
CLIMATE PRIORITY
I was troubled by “What to Do about Natural Gas,” Michael E. Webber’s article about ways to decarbonize the natural gas system. Pointing out that the primary alternative, electrification, will be challenging is fair enough. But electrification does not have barriers that are greater than, or even equal to, a zero-carbon gas system, which faces structural limitations. To his credit, Webber names some of these limitations. But his presentation of them as solvable with some tweaks is disingenuous. Even by the gas industry’s own estimates, two decades of scaling up all low-carbon gases would displace only about 13 percent of the U.S.’s existing gas demand. Also, it would squander any genuinely sustainable gases that could be used where we might actually need them, such as chemical feedstocks, shipping and aviation.
Keeping warming within the 1.5 degrees Celsius limit necessary to avoid catastrophic climate destabilization requires us to reach net-zero emissions, meaning we must leave the majority of the world’s existing gas reserves unburned. And whether methane is synthetic, biogenic or fracked, if it’s pumped through the existing distribution network, it will face leakage, adding to atmospheric warming.
Perhaps the most important omission is that decarbonizing gas does not solve the health impacts of combustion. With low-carbon gases, we only get more expensive ways of polluting our homes.
SASAN SAADAT Research and policy analyst, Earthjustice
WEBBER REPLIES: It seems that we agree that addressing climate change is the most urgent and important challenge of the 21st century. That realization led me to the conclusion that we need every solution possible to get us to carbon neutrality (and carbon negativity!) as quickly, safely and affordably as possible. As I write in the article, I think the first two priorities for decarbonizing the economy are (1) conservation and efficiency and (2) electrification. Because low-carbon fuels play an important role for sectors that are difficult to electrify, we need to make progress on decarbonizing gases as the third step.
As someone who invented sensors to measure the emissions from combustion, I’m well aware of its pollution. And as someone who quantitatively analyzes different forms of energy, I’m also aware of the significant ecosystem impacts of some utility-scale renewables. The energy system is all about trade-offs, and there is no one fuel or technology option that is purely villainous or virtuous. Rather we must design a suite of solutions that meets society’s complex needs.
PREDICTIONS AND MEMORY LOSS
In “Prediction Predicament” [Advances], Hannah Seo notes that making predictions impairs people’s ability to remember predictive events. I see this a lot in the martial arts. Often when an instructor demonstrates a technique, the students will be busy imagining what comes next and how they think the technique should be performed while failing to see the variation that the instructor is demonstrating. It’s like the students are watching to confirm their predictions instead of observing to learn something new.
IAN MCINTYRE via e-mail
RECOVERING FROM ADDICTION
“Hope for Meth Addiction,” by Claudia Wallis [Science of Health], encouragingly describes the growing evidence base for contingency management as an effective treatment for stimulant use disorder, particularly in conjunction with bupropion and naltrexone. It notes that one trial of the two drugs found that they helped a significant number of treated users test methamphetamine-free “at least three quarters of the time.”
Wallis’s piece is to be applauded for its apparent recognition that complete abstinence is not the only recovery pathway. Harm reduction is effective, and reoccurrence of substance use is not unusual for most people as they seek recovery. While abstinence-based approaches may be ideal for some, they don’t work for everyone. Contingency management and harm reduction are both important strategies that can lead to improved health and wellness for those who are still struggling with harmful substance use.
Ann Herbst Interim CEO, Young People in Recovery
ERRATA
In “The Math of Making Connections,” by Kelsey Houston-Edwards, the bottom illustration in the box “Square Lattice” should have depicted the white pipe at the top left of the lattice filling with water.
In “Scientists: Admit You Have Values,” by Naomi Oreskes [Observatory], the end of the quote attributed to Francis Bacon should have read: “… man prefers to believe what he wants to be true.”
