Category: MIL-OSI

Source: The Conversation – UK – By Louise Burgess, Lecturer in Sport and Exercise Science, Bournemouth University

An estimated 595 million people globally are living with osteoarthritis. This makes it one of the leading causes of pain and disability.

Osteoarthritis is a degenerative joint disease, in which tissues in the joint break down over time. The condition can affect any joint, but most commonly the knees, hips, hands and spine.

However, the impact of osteoarthritis often goes beyond the affected joint. The condition can have profound effects on daily life.

Research shows that people with osteoarthritis are less likely to remain in work and more likely to develop additional health problems, such as diabetes, obesity and poor mental health, than those without the disease.

One of the key approaches recommended for managing osteoarthritis is exercise, including aerobic exercise and muscle strengthening. It’s shown to be extremely beneficial for managing the condition and its associated symptoms.

But not everyone who has osteoarthritis is able to exercise due to pain and limited mobility. This is why electrical muscle stimulation, a novel technology that uses small electrical impulses to help muscles contract, is being investigated for managing osteoarthritis.

Exercise for osteoarthritis

Aerobic and muscle strengthening exercises are both proven to address key drivers of osteoarthritis symptoms.

Aerobic exercise can help manage body weight and improve pain by enhancing circulation and reducing inflammation.

Muscle strengthening exercise improves joint stability by supporting the surrounding musculature. This reduces stress on the joint and improves movement.

Together, these approaches can help to break the cycle of pain, inactivity, weight gain and physical decline that can happen in osteoarthritis.

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Read more:
Joint pain or osteoarthritis? Why exercise should be your first line of treatment

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But as beneficial as exercise is, many people with osteoarthritis are reluctant to try it or struggle to adhere to physical activity long term.

In fact, data suggests that people with musculoskeletal conditions (such as osteoarthritis) are around twice as likely to be physically inactive as their healthy counterparts.

Reported barriers to physical activity include pain, limited mobility, negative experiences of physical activity and a lack of motivation. But the less we move, the more muscle mass and strength we gradually lose.

A difficult cycle can then emerge, whereby pain, stiffness and fear of making symptoms worse all discourage movement. Then, without movement, stiffness and pain worsen.

An alternative approach

When exercise feels too painful or isn’t possible, electrical muscle stimulation (EMS) may offer an alternative method for maintaining and improving strength.

This works by placing electrodes on the skin to deliver small electrical impulses, causing muscles to contract without the joint needing to move. The electrical impulse is similar to the signal we normally send from our nervous system when we want to perform a movement.

When performed instead of exercise over several weeks and sessions, EMS has been shown to increase muscle size and strength and improve function in people with hip and knee osteoarthritis. For example, in people with knee osteoarthritis, EMS performed on the quadriceps muscles three days per week for 4-8 weeks has led to benefits.

The therapy can be used in isolation, or it can be applied during exercise to activate even more muscle fibres in what is called a superimposed muscle contraction.

Electrical muscle stimulation also shows promise for those with severe, end-stage osteoarthritis who are preparing for surgery.

For example, one study compared the effects of performing EMS or exercise before surgery for knee osteoarthritis on postoperative outcomes. The study found that participants who used EMS for 20 minutes a day, five days a week in the six weeks before surgery saw greater improvements in postoperative muscle mass, strength and function, compared with patients who performed physical exercise.

Muscle weakness is common both before and after surgery, partly due to pain and reduced movement. While exercise programmes before and after surgery are widely recommended, research suggests they often only have modest effects on functional recovery from joint replacement surgery.

One explanation may be that people with severe osteoarthritis cannot tolerate the level of intensity needed while exercising to build muscle effectively. In addition, joint trauma and swelling from surgery can cause disruption to the signalling pathways that are required to activate muscles.

Because EMS can bypass some of these signalling issues, it may help to maintain or rebuild muscle where conventional exercise is not feasible immediately after surgery. It’s often used in sports settings for this reason, such as when athletes require anterior cruciate ligament surgery.

Not a replacement for exercise

That said, electrical muscle stimulation is not a magic solution and has its limitations. In many cases, it works best as a complement to, not a substitute for, active rehabilitation.

The body of evidence for its effectiveness in osteoarthritis is also still evolving. Some studies showed inconsistent results or were only conducted using a small sample.

Some people find the sensation of electrical stimulation uncomfortable. Some aren’t suitable for its use (for example, those with pacemakers) and devices can be expensive to buy.

Nonetheless, for those who cannot exercise due to pain, swelling or limited mobility, EMS offers a practical tool to maintain muscle strength. This can help them stay active and independent for longer, recover quicker from surgery, and maintain a better quality of life.

Louise Burgess does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.

– ref. Osteoarthritis: how stimulating the muscles with electricity may help manage the condition – https://theconversation.com/osteoarthritis-how-stimulating-the-muscles-with-electricity-may-help-manage-the-condition-281601

Source: The Conversation – UK – By Jennifer Loudon Moxen, PhD Candidate, COPD Inflammation, University of the West of Scotland

Chronic obstructive pulmonary disease, or COPD, is one of the world’s leading causes of death, responsible for 3.5 million deaths in 2021 alone. It is often thought of as a disease of older smokers. But that picture is too simple. COPD usually develops slowly over many years, often long before symptoms become obvious.

COPD is a long-term lung condition that makes it harder to move air in and out of the lungs. It includes damage to the airways, often described as chronic bronchitis, and destruction of the tiny air sacs in the lungs, known as emphysema. Because this damage builds up gradually, many people do not realise anything is wrong until symptoms become difficult to ignore. There are treatments that can help, but there is no cure, and by the time COPD is diagnosed the damage is often permanent.

Common symptoms include a long-term cough, bringing up mucus and shortness of breath. These symptoms often appear later in life, which helps explain why COPD is so often seen as an older person’s disease. But in many cases, the damage started decades earlier.

Many environmental irritants can harm the lungs, but cigarette smoke remains the main cause of COPD. Cigarette smoke contains thousands of chemicals, including toxic gases and cancer-causing substances, that injure lung tissue and trigger oxidative stress, a form of cellular damage that drives inflammation.

Inflammation is part of the body’s normal defence and repair system. Usually, it settles once the source of harm has gone. But in COPD, the lungs may be exposed to cigarette smoke day after day, so the inflammatory response never properly switches off.

Over time, immune cells sent to repair the damage can end up injuring the lungs further. The airways become narrower, the lungs produce more mucus, and the tiny air sacs known as alveoli can break down. Together, these changes make breathing increasingly difficult.

As the disease progresses, the lungs are physically altered in ways that cannot be fully reversed, even if someone stops smoking. COPD inflammation also does not always respond well to standard anti-inflammatory medicines such as steroids, which is one reason prevention matters so much.

Although cigarette smoking remains the main driver of COPD, e-cigarettes are also raising concerns. Vaping aerosols can contain nicotine, ultrafine particles and flavouring chemicals that may irritate the lungs and contribute to inflammation. The long-term effects are still unclear because these products are relatively new.

That matters particularly for younger people. In Great Britain, recent survey data suggest that 7% of 11- to 17-year-olds currently vape. While that does not mean they will go on to develop COPD, it does mean more young lungs are being exposed to substances whose long-term effects are not yet fully understood.

COPD is often diagnosed only after major lung damage has already occurred. Because it develops so gradually, people may dismiss early breathlessness, coughing or mucus production as a consequence of getting older, being unfit or smoking. Respiratory organisations warn that symptoms such as cough, phlegm and shortness of breath should not be treated as a normal part of ageing, while studies show that COPD remains widely underdiagnosed, including among people with respiratory symptoms.

The burden on health systems is huge. A 2023 study estimated that COPD could cost the global economy around INT$4.3 trillion between 2020 and 2050. International dollars adjust for differences in prices between countries; in broad terms, this is roughly equivalent to US$4.3 trillion in US purchasing power, or about £3.2 trillion if treated as US dollars at current exchange rates. Hospital admissions often rise in winter, when people with COPD are more vulnerable to bacterial and viral infections that can worsen symptoms and speed up decline.

That is why the most important window for action may come much earlier in life. By the time many people are diagnosed, the disease has been developing for years. Better education about lung health at school age could help people understand that choices made in their teens and twenties may shape their breathing decades later.

COPD care has traditionally focused on treating symptoms once they appear. But by then the lungs may already be permanently damaged. Seeing COPD as a disease that develops slowly over decades could shift attention towards earlier prevention and, ultimately, reduce its human and economic cost.

Jennifer Loudon Moxen does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.

– ref. Chronic obstructive pulmonary disease develops over decades – and we are missing the window to prevent it – https://theconversation.com/chronic-obstructive-pulmonary-disease-develops-over-decades-and-we-are-missing-the-window-to-prevent-it-278473

Source: The Conversation – UK – By Nick Chater, Professor of Behavioural Science, Warwick Business School, University of Warwick

Feelings of despair at the state of the world can be overwhelming. Social and environmental problems persist, but political discourse is polarised, divisive and often ineffective.

A couple of decades ago, some behavioural scientists – ourselves included – began to think there might be a better way of addressing these challenges.

Instead of relying on governments to change things, we figured, perhaps we should switch the focus to people’s own actions. And maybe improving their choices would provide an alternative route to social and environmental transformation.

The idea developed from the fact that people sometimes make bad decisions which may be harmful – to themselves, to others or to the environment.

So what if we tried to discourage things like smoking or frequent flying, not with the heavy hand of government, but by appealing directly to the psychology of the individual?

Two pioneers of this approach, Richard Thaler and Cass Sunstein, argued that governments and institutions could “nudge” people by subtly redesigning the decision-making process. A typical nudge might involve making certain arrangements the default option, such as automatic enrolment into pension schemes. Or it might mean placing healthier meals first on menus.

In these situations, nothing needs to be banned. The undesirable options remain available – they’re just tucked away or more difficult to access.

Behaviour gets nudged along in personally and socially beneficial directions, without removing freedom of choice, and without getting into politically contentious territory. Like many enthusiasts, we were optimistic that focusing on individual behaviour might prove to be an effective route to a better world.

Sadly, things turned out rather differently.

Recent results from large meta-analyses (studies that bring together findings from many previous experiments) suggest that the effects of nudges and other individualistic interventions are disappointingly small.

Some authors have even concluded that there may be no reliable evidence that nudges work at all. Other evidence suggests that even when nudges do have an effect, those effects are small, short lived and difficult to scale up.

And there is another problem, as we argue in our new book It’s On You. By focusing attention on individual responsibility for the world’s problems, behavioural scientists may have inadvertently assisted a broader process known as “responsibilisation”“.

Responsibilisation means placing the burden of blame onto individual consumers – deflecting attention from the need to regulate or constrain big businesses which benefit and profit from maintaining the status quo.

Oil companies for example, might want the world to focus on the responsibility of individual car drivers and frequent flyers. Plastics and packaging companies stress the scourge of individual littering. Manufacturers of ultra-processed foods and sugary drinks want us to blame ourselves for poor diets.

In each case, individual behaviour is placed centre stage, while the need for regulations to shift corporate practices recedes from view.

And persuading us to place responsibility on the individual goes very much with the grain of human psychology. Our social lives are built around interacting with small numbers of other people, even while we are governed by complex systems of norms, conventions and rules that change slowly. Systems that we largely take for granted, do not control and rarely even notice.

Taking responsibility

It is hardly surprising then, that when we look for explanations for social problems such as climate change or gun violence, we naturally attribute them to the actions of bad people. It’s the drivers of big cars or violent types with mental health problems.

This means that people are wired to be all too ready to buy into the responsibilisation narrative that individuals, including ourselves, are at the heart of the problems that bedevil society.

But when social problems arise and intensify, it is unlikely that human nature has suddenly deteriorated en masse.

It is far more plausible that large-scale systemic forces – changes in regulation, market structure, technology and incentives – are at work. And when problems are systemic and self-reinforcing, systemic solutions are what is required.

In a world that feels increasingly contentious and imperilled, it is tempting to hope that individual consumers can really make a difference – to imagine that we can improve the world one recycled yoghurt pot at a time. And each of us should, of course, do our bit by making good consumer choices where we can.

But we must not allow a focus on the individual to distract us from the need for deeper systemic change. Gentle nudges will never be enough. To address our persistent social and environmental challenges, we need the collective political will to reshape the rules that govern all of our lives.

Nick Chater receives funding from UKRI and NSF. I am also a co-founder of Decision Technology, a behavioural science consulting company founded in 2002 (and I continue to be a share-holder and director). The company doesn’t stand to benefit from this article (if anything, the reverse!).

George Loewenstein does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.

– ref. Nudge theory was all about taking responsibility – but it allowed big business to look the other way – https://theconversation.com/nudge-theory-was-all-about-taking-responsibility-but-it-allowed-big-business-to-look-the-other-way-278357

Source: The Conversation – UK – By Michael J. Benton, Professor of Vertebrate Palaeontology, University of Bristol

A great Tyrannosaurus rex strides through the conifer trees of her territory, sniffing the air. She picks up the scent from the carcass of a dead horned dinosaur, Triceratops, that she was feeding on yesterday. She walks over and strips off some more shreds of meat, but the smell is foul even for her.

She goes down to the lake to drink and small crocodiles and turtles scuttle into the water. But she hardly sees them. Of more interest is an armoured dinosaur, Ankylosaurus, lurking nearby. However, she knows this dinosaur won’t be an easy kill and she isn’t desperate enough for food to risk a fight. Little does she know there are bigger dangers ahead. She looks up and sees a bright light racing downwards accompanied by faint crackling and sizzling noises.

Our T. rex has excellent hearing for low frequency sounds and she is disturbed by the vibrations she can feel. But her upset only lasts for a moment. In a flash, she has been burnt to a crisp and her world changed forever.

This all happened 66 million years ago, when a huge asteroid famously hit the Earth in the area of what is now the Caribbean. At the end of the Cretaceous period, sea levels were 100–200 metres higher than today, so the shores of the Caribbean lay far inland over eastern Mexico and the southern United States. The impact happened entirely within these waters.

The event triggered instant changes to our planet and its atmosphere and led to the extinction of the dinosaurs and about half Earth’s other species. But what would it have been like to experience such an gargantuan impact? What would you have seen, heard or smelled? And how would you have died – or survived?

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The Insights section is committed to high-quality longform journalism. Our editors work with academics from many different backgrounds who are tackling a wide range of societal and scientific challenges.

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As experts on meteoritics and palaeontology, respectively, we’ve created a detailed timeline, based on decades of research, to take you right there. So let’s start by travelling back in time to the very last day of the Cretaceous.

T-minus one day

All is calm and the Cretaceous day proceeds as usual. In what will soon be ground zero, it is pleasantly warm, about 26°C, and wet. It often is. For about a week, the asteroid has been visible only at night. Because the giant rock is heading straight towards Earth, it looks like a motionless star. There is no dramatic tail; this is a rocky asteroid rather than a comet.

In the last 24 hours, the light becomes visible during the daytime. But it still looks like a star or planet, getting as brighter in the final few hours before impact.

T equals 0: the impact

If you were close by, you would first have experienced a brief light and sound show. Minutes to seconds before the impact, you’d have seen the bright fireball, and its accompanying crackling or fizzing noises. This sizzling sound is a result of the photo-acoustic effect: the intense light of the fireball warms the ground, which then heats the air above it, causing pressure waves, or sound.

Next, a deafening sonic boom, which occurs because the asteroid is travelling faster than the speed of sound. But the asteroid is so huge, perhaps 10km in diameter, that it almost certainly hits the ground before any living creature near the impact zone has time to run for cover.

The asteroid’s enormous energy forms a crater through a series of processes that together take only a few seconds. As the asteroid collides with the surface, its kinetic (movement) energy is instantly transferred to the surface as a combination of kinetic, thermal (heat) and seismic energy (released during earthquakes). This results in a series of shock waves that heat and compress both the asteroid and its target.

As the shock waves propagate, rocks fracture, break up and are ejected, producing a bowl-shaped depression, or transient cavity, about ten seconds after impact. The heat and compression also melt and vaporise large volumes of material, including the asteroid itself, releasing a fountain of incandescent vapour (its temperature is more than 10,000 K, or 9726.85°C).

Over the next few seconds, the cavity increases in size to many times the diameter of the original asteroid. Simulations suggest that around 20 seconds after impact, the transient cavity is at least 30km deep – deeper than the deepest depth currently known on Earth, the 11km Challenger Deep valley, part of the Pacific Ocean’s Marianas Trench. The rim of the crater is over 20km high – more than twice the height of 8,900m Mount Everest.

But this enormous feature lasts for less than a minute before it starts to collapse. Within three minutes of the impact, the centre of the crater has rebounded to form a peak several kilometres high. The peak only lasts about two minutes before collapsing back into the crater.

Whether a dinosaur or a dung beetle, if you were near the transient cavity you would have been incinerated instantly by the blast. But even if you were up to 2,000km from the epicentre, you’d likely have been killed quickly by the thermal radiation and supersonic winds now spreading out from the impact site.

T-plus 5 minutes

Five minutes after the impact, the winds have “eased” to those of a category 5 hurricane, flattening everything within about 1,500km of the impact. Destroying everything, that is, which has not already been burnt. Atmospheric temperatures in the region rise to over 500K (226.85°C). This would feel like being inside an oven – causing burns, heatstroke and death. Wood and plant matter ignite, creating fires everywhere.

Because the asteroid struck the sea, the atmosphere is also filled with super-heated steam, making the hurricane-force winds even deadlier.

Next come the tidal waves, triggered by the vast quantities of displaced rock and water. These 100-metre megatsunamis first strike the shores of what is now the Gulf of Mexico, engulfing the land before depositing huge amounts of debris as they retreat.

By now, the crater has almost reached its final dimensions – 180km across and 20km deep. But making an enormous hole in the ground isn’t the only outcome of the impact. All the rock and vapour displaced during the collision has to go somewhere. Several locations in Northern America show that metre-sized blocks of debris from the impact were thrown distances of hundreds of kilometres.

So if you were 2,000km to 3,000km from the epicentre and survived the first few seconds, you’d most likely die from overheating, earthquakes, hurricanes, fires, tsunami-driven floods or being hit by impact melt.

But what is happening much further away? In the first five minutes after impact, dinosaurs roaming the Cretaceous forests of what are now China or New Zealand are so far undisturbed.

But it won’t be long before that changes.

T-plus one hour

Shockwaves on land and sea are only minor inconveniences compared with the fire that is still radiating down from the sky. Some of the impact energy has been transferred into the atmosphere, heating the air and dust to incandescence.

An hour after impact, a belt of dust has circled the globe. Deposits of solidified molten droplets (impact spherules) and mineral grains have been found in numerous locations from New Zealand in the south to Denmark in the north. In these locations, you would not have been aware of the tsunamis around the Americas or the wildfires, but the skies would certainly have begun to darken.

T-plus one day

By now, huge tsunamis are moving east across the Atlantic and west across the Pacific, entering the Indian Ocean from both sides.

They are still around 50m high – causing death and destruction across many coasts around the world. By comparison, the 2004 Boxing Day tsunami reached heights of up to 30 metres. Tsunamis kill fishes and marine life that are washed high on the shore and then dumped, just as they kill coastal trees and drown land animals. But the tsunamis gradually fade away and probably don’t wipe out any entire species – at least on their own.

The hurricane force winds have also died down, but tropical storm strength winds are whipping up debris and causing further chaos and destruction across the tsunami-affected areas. The burning sky is also triggering wildfires across the globe – which, in turn, carry ever more soot into the atmosphere. The sooty signature of these wildfires has been found deposited as carbon particles in sediments from the K-Pg boundary – a 66-million-year-old thin clay layer.

Further away, in what is modern Europe and Asia, the skies continue to fill up with dust and soot, as they do everywhere. Temperatures start to drop as sunlight is blocked. Trees and plants in general, including phytoplankton, close down as if for winter, unable to photosynthesise. Any animals that rely on warm conditions ultimately hunker down and die.

T-plus one week

It’s getting darker and darker. Simulations of solar radiation reaching the Earth’s surface following the impact indicate that, after about a week, the solar flux (the amount of heat and light per a certain area) is just one thousandth of that prior to the impact. This is caused by particles of dust and soot in the atmosphere.

The continued decrease in light levels is accompanied by a global drop in surface temperatures of at least 5°C. This means that most of the dinosaurs and other large flying and swimming reptiles probably die from freezing within the course of this first week (smaller reptiles with slower metabolisms or more flexible diets could survive longer). Cooling temperatures and cloud cover also lead to rain. But not just any rain. Storms of acid rain fall across the Earth.

Two separate mechanisms generate acid rain. The first is down to the geology of the impact region. The asteroid happened to hit an area of sediments rich in sulphur, which vaporised and caused sulphur oxides (acidic and pungent gas compounds composed of sulphur and oxygen) to be part of the plume of plasma blasted into the atmosphere. Second, the energy of the collision was sufficient to turn nitrogen and oxygen into nitrogen oxides – highly reactive gases that can form smog.

The dropping temperature ultimately allows water vapour to condense into drops, and the sulphur and nitrogen oxides dissolve to form sulphuric and nitric acids. This is sufficient to generate a rapid drop in pH. Early models suggest that the pH of the rain might be as low as 1 – the same acidity as battery acid.

At this point, Earth is not a great place to be. Rotting vegetation, choking smoke and sulphur aerosols combine to make the planet stink. Plants and animals on land and in shallow seas that have survived the darkness and cold succumb to the corrosive acid rain and ocean acidification. Acid rain also kills trees by leaching nutrients such as calcium, magnesium and potassium from the soil. Shallow marine shellfish, crustaceans and corals also die as acid seawater destroys their skeletons.

T-plus one year

Winds die down, wildfires are extinguished and the oceans are once again calm. It might appear that the asteroid collision is just a scar on the ocean floor. But its effects are still destructive. The atmosphere is still filled with dust and the Sun hasn’t shone for a year. Temperatures have continued to drop, with the average surface temperature now 15°C lower than before the impact. Winter has come.

Any dinosaurs or marine reptiles that survived the first week of freezing conditions would have died very soon after. A year after the impact, only rotted skeletons of these behemoths remain. Here and there, smaller animals like mammals the size of rats and insects would be nestling in crevices, barely surviving on their reserves and decaying plants.

Indeed, it has not been a good year for life on Earth: over 50% of plants have died out because of the cold and lack of sunlight. And similar losses have occurred among terrestrial animals and species in the acidified, shallow sea waters.

While most plant groups and many of the modern groups of insects, fishes, reptiles, birds and mammals recover reasonably rapidly, things don’t look great for other species. Dinosaurs and pterosaurs living on land are extinct, as are many marine reptiles, ammonites, belemnites and rudist bivalves in the oceans. Ammonites and belemnites are high in their food chains, and so suffer not only from the cold and acidification but also from the loss of abundant food resources, such as smaller marine organisms.

T-plus ten years

The Earth is still in the grip of a fierce winter. Although most of the sulphur has rained out of the atmosphere, dust and soot particles remain. The average surface temperature is still about 5°C lower than before the impact. The main oceans have not frozen, but inland lakes and rivers around the world are iced over.

Surviving plant and animal groups such as turtles, smaller crocodiles, lizards, snakes, some ground-dwelling birds and small mammals repopulate the Earth at this point. But they are forced back to limited areas of relative safety a long way from the impact site. These areas are now receiving sufficient sunlight for plants and phytoplankton to photosynthesise again. As leaves and seeds provide the basis for the food chains on land and in the sea, life begins to rebuild.

Eventually, life returns to the devastated landscapes, but ecosystems are very different and the dinosaurs are no more.

T-plus 66 million years

Today, 66 million years after the impact, the scars of the collision are hidden within geological strata – and scientists have started deciphering them. It was in 1980 that researchers first reported evidence of the impact. In their classic paper, Luis Alvarez, a Nobel-prize-winning physicist, and co-authors, described a sudden enrichment in the element iridium in a specific clay layer in Denmark and in Italy.

Iridium is rare in surface rocks because most of it was sequestered in Earth’s core when the planet first formed. However, iridium is found in meteorites, and Alvarez and colleagues inferred that the rate of accumulation of the metal in the sediments was so high that it could only have been produced by impact of a gigantic meteorite.

Because the scientists had only observed the iridium spike in two locations, the impact hypothesis was rejected by many scientists at the time. However, through the 1980s, iridium spikes were identified in clay layers at more and more locations – in muds laid down on land, in lakes, in the sea.

Support for an impact hypothesis strengthened when a crater of the correct age was found in 1991. The crater is buried beneath younger rocks, but clearly visible in geophysical surveys, lying half on land in the Yucatán Peninsula of Mexico, and half offshore. Since 1990, evidence for the impact has increased, not least when scientists discovered that there was indeed a sharp cooling event at the end of the Cretaceous.

In total, it is estimated that half the species of plants and animals alive at the end of the Cretaceous disappeared. It was once thought that surviving groups such as many plants, insects, molluscs, lizards, birds and mammals somehow escaped unscathed. But detailed study shows that this is not the case – they were all hit hard.

But, by chance or luck, enough individuals and species were able to survive the cold and absence of food, or were in parts of the world where the effects were less extreme. As the world returned to normal, they had the opportunity to expand rapidly into their old niches, but also to occupy the space vacated by extinct groups. In fact, one important consequence of the extinction of the dinosaurs, apex predators in their heyday, was the successful spread and evolution of mammals.

When Alvarez and colleagues first described the drop in temperature following the impact, they called it a “nuclear winter”, reflecting the political climate of the early 1980s. Now we might be more inclined to describe the effects as a global climate change – similar events are currently resulting from increased carbon dioxide in the atmosphere (flooding, temperature fluctuations).

It is salutary to think that without the asteroid collision, primates might never have reached the level we are at today. But it is equally salutary to consider that modern humans are causing some of the same changes to the atmosphere that ultimately killed our reptilian forbears and may one day also lead to our own demise.

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Monica Grady receives funding from the Leverhulme Trust for an Emeritus Fellowship and from the STFC. She is affiliated with The Open University, Liverpool Hope University and the Natural History Museum, London.

Michael J. Benton does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.

– ref. What it would have been like to experience the dinosaur-killing asteroid armageddon: a blow-by-blow account – https://theconversation.com/what-it-would-have-been-like-to-experience-the-dinosaur-killing-asteroid-armageddon-a-blow-by-blow-account-271786