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Our climate seems to be more sensitive to greenhouse gas emissions than someresearchershad hoped, meaning the world will have to up its decarbonisation efforts

Climate change could be even worse than we thoughtKapook2981/Getty Images

Climate change could be even worse than we thought

Earth’sclimatemay be more sensitive to pollution from greenhouse gas emissions than we had hoped, which could mean limiting the rise in global temperature to less than 2°C will be more difficult.

This is “bad news” for global efforts to tackle climate change, saysGunnar Myhreat the CICERO Center for International Climate Research in Norway.

Read moreThe jet stream may be starting to shift in response to climate change

The jet stream may be starting to shift in response to climate change

Researchers have known for decades that pumpinggreenhouse gasesinto Earth’s atmosphere will warm the climate, with far-reaching consequences. But what scientists do not know for sure is how much warming we can expect as a consequence of this pollution. In other words, how sensitive is Earth’s climate to these emissions?

The main uncertainty stems from the question of how clouds will respond to a warming atmosphere, as shifts in cloud systems can amplify the warming effect in a vicious feedback loop.

Most estimates of how much warming we can expect by the end of the century are based on running climate models with a range of sensitivity assumptions. Models used by the Intergovernmental Panel on Climate Change suggest that a doubling of atmospheric CO₂ concentrations relative to pre-industrial levels would produce between 2°C and 5°C of warming, with the organisation settling on a central estimate of 3°C.

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Alongside his colleagues, Myhre set out to compare predictions from these climate models againstsatellite readings of Earth’s energy imbalance. This is a measure of how much surplus heat is in our climate system, and it gives an indication of the sensitivity level of the global climate.

The team found that climate models with low sensitivity – those that suggest Earth’s climate is more resistant to greenhouse gases in the atmosphere – don’t match satellite records gathered since the turn of the millennium. Models with a higher level of sensitivity, suggesting Earth’s climate is less resistant to these gases, more closely match observations, says Myhre. “The optimistic models that would give us a small amount of warming are more unlikely,” he says.

The findings call into question the accuracy of climate models that predict less than 2.9°C of warming for a doubling of atmospheric CO₂. Instead, they suggest warming above this level is more likely for the same amount ofpollution.

This also tallies with recent record-breaking temperatures recorded over land and sea since 2023, which “point towards a stronger climate feedback” in the atmosphere, says Myhre.

Is climate change accelerating and is it worse than we expected?With temperature records tumbling, it is only natural to worry about cascading tipping points, but the reality is far more nuanced

Is climate change accelerating and is it worse than we expected?

With temperature records tumbling, it is only natural to worry about cascading tipping points, but the reality is far more nuanced

A more sensitive climate means emissions must fall faster to maintain the same temperature trajectory. In short, the world has to decarbonise further and faster to fulfil its climate commitments.

Johannes Quaasat the University of Leipzig in Germany says the research presents a “very plausible argument” that Earth is more sensitive to warming than some models suggest, adding that it has “narrowed the range” of model estimates that scientists should work from. “It underlines the need for political action against climate change.”

Richard Allenat the University of Reading in the UK points out that the satellite record only began in 2001, so “natural climate fluctuations” could also form part of the story. Nevertheless, he says the study is “rigorous” and “adds more evidence that simulations which predict less warming in the long term are less realistic”.

Journal reference:ScienceDOI: 10.1126/science.adt0647

ScienceDOI: 10.1126/science.adt0647

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A simulation of the "aerial screw" designed by Leonardo da Vinci in 1480 suggests it would use less power than modern drone rotors to generate the same lift, and make less noise too

Leonardo da Vinci’s sketch of the aerial screwGianni Dagli Orti/Shutterstock

Leonardo da Vinci’s sketch of the aerial screw

A flying machine designed by Leonardo da Vinci may have been functional and much quieter than modern drone designs.

Rajat Mittalat Johns Hopkins University in Maryland and his colleagues have found that da Vinci’s “aerial screw”, which he proposed while working as a military engineer in the 1480s but never built or tested, may require less power to generate the same amount of lift as a conventional drone rotor.

Read moreDrone versus drone combat is bringing a new kind of warfare to Ukraine

Drone versus drone combat is bringing a new kind of warfare to Ukraine

The machine is similar to an Archimedes’ screw, a helix-shaped pump that transports water as it rotates. Da Vinci envisaged the aerial screw as being powered by humans, which would have made it challenging to get off the ground due to weight. But with light electric motors spinning the rotor, it could have actually flown.

Mittal and his team built a simulation of the screw and put it in a virtual wind tunnel to see how it would perform while hovering in place, testing it at different rotational speeds and comparing it with a conventional drone rotor with two blades.

They found the aerial screw could generate the same amount of lift while rotating more slowly, meaning it would consume less power.

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By measuring the pressure and wind flow patterns that moved around the virtual screw, Mittal and his team could also calculate how much sound it might produce, which they found was less than the conventional design for the same amount of lift.

“We were surprised,” says Mittal. “We went in thinking that because the shape of this spiral screw is just completely, in some sense, ad hoc, it was intuitive that the aerodynamic performance would be so bad that we would not be able to get any improvements over conventional blades.”

Mittal and his team now want to see if they can improve upon da Vinci’s design to make it more efficient while keeping its noise-reducing qualities, he says.

Read moreSupersonic flight will see a dramatic return in 2025 with new aircraft

Supersonic flight will see a dramatic return in 2025 with new aircraft

As drones are increasinglyused in cities, such as for home deliveries or emergency services, noise pollution has become more of a problem, leading to researcherslooking for newrotor designs that create less noise for a similar amount of lift.

“The authors do a good job of stating that if you can create the same thrust by turning slower, which the da Vinci [rotor] does, then the noise is going to be less,” saysSheryl Graceat Boston University in Massachusetts. “It doesn’t have to be the da Vinci design to achieve this, but it is nice that da Vinci’s does.”

However, to show that da Vinci’s design could be useful in real-world scenarios, they would need to test how it performs while flying through the air, rather than just hovering, as well as consider how the extra weight of the rotor might affect performance, says Grace.

Reference:arXivDOI: arXiv:2506.10223

The science of the Renaissance: ItalyEncounter the great scientific minds and discoveries of the Renaissance, which helped cement Italy’s role at the forefront of scientific endeavour.Find out more

Encounter the great scientific minds and discoveries of the Renaissance, which helped cement Italy’s role at the forefront of scientific endeavour.

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Over the past 150 years, the rise in Caesarean sections and changes in diet could have led to smaller pelvises among women – which may make vaginal birth more difficult but could also reduce common conditions associated with childbirth

Medical advances have changed childbirth – potentially enough to impact human evolutionFatCamera/Getty Images

Medical advances have changed childbirth – potentially enough to impact human evolution

Women’s pelvises have become narrower over the past 150 years, according to a study of over 8000 people from three countries. There are many factors at play, but whatever the ultimate cause, it is the latest piece of evidence leading researchers to rethink the “obstetrical dilemma”, a description of the competing evolutionary pressures on pelvis size: the need to accommodate babies’ large heads drives pelvises to widen, but the need to walk bipedally pushes them to narrow.

Read moreThe biggest coincidence in human evolution

The biggest coincidence in human evolution

We don’t know exactly what is driving this change, or all the ways it will affect people’s health. But if pelvises continue shrinking at this pace, it could make Caesarean sections more likely out of necessity – which could have a host of knock-on effects.

Maciej Hennebergat the University of Adelaide in Australia and his colleagues reanalysed an existing dataset of 1247 Australian women, born between 1900 and 1984, and found that pelvic width decreased by 0.42 millimetres per year. Likewise, among 3486 Polish women, pelvis widths decreased by 0.47 mm per year between 1880 and 1970, and among 320 Mexican women, pelvis width shrank by 0.42 mm per year between 1900 and 1970. In the same time periods, average height increased and shoulder width either held steady or increased.

“Given that in these different regions, it evolved in the same direction, even though body height increased, I personally find this convincing,” saysPhilipp Mitteroeckerat the University of Vienna in Austria.

“The dataset is fantastic,” saysLia Bettiat University College London.

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For Henneberg, this finding shows that modern medicine is weakening natural selection’s impact on the human pelvis – and especially on the width of the birth canal. In the past, if a baby was too large or the birth canal was too narrow, both mother and baby would probably die in childbirth. However, safe and effectiveCaesarean sections, or C-sections – in which the baby is removed surgically through the abdomen – mean this evolutionary pressure is reduced. As a result, birth canals and pelvises can become narrower.

Mitteroecker also thinks C-sections are changing the evolutionary pressures at work on the human birth canal. He predicted that this might drive pelvises to narrow ina 2016 analysis, and says this is the latest iteration of a long-standing phenomenon.

“Midwifery is old,” he says, and “really unique to humans”. Women have been getting help with childbirth, often from other women,for hundreds of thousands of years. This cultural practice hasrelaxed the selection pressure on the pelvis and birth canal– so our behaviours have affected our own biological evolution. “C-section is, in a way, an extreme form of that,” says Mitteroecker. C-sections took off starting in the 1970s through the 1990s, and the global rate increased from7 per cent in 1990 to 21 per cent in 2021.

Read moreWhy did humans evolve big brains? A new idea bodes ill for our future

Why did humans evolve big brains? A new idea bodes ill for our future

However, Betti is sceptical that C-sections are the main explanation for the recent change in pelvic width. She points out that humans got a lot taller in the same time frame, but that is probably due to diet and better healthcare – not an evolutionary change in our genes.

“We know that diet can affect the pelvis,” says Betti. When nutrition is scarce, our developing bodies tend to allocate more nutrients to certain organs, including the brain, at the expense of others. But now we have ample nutrition, so our bodies may have reallocated nutrients. “So we end up with different body proportions,” says Betti. “That’s quite possible.”

Finding an explanation for our narrowing pelvises could help us understand why human childbirth is so difficult – which brings us back to the obstetrical dilemma. However, the exact nature of the dilemma has been disputed. In a 2024 study, Mitteroecker and his colleagues found that thepelvic floor, not walking, was probably the key driver towards narrowness: wider pelvises increase the already high pressure on the pelvic floor, boosting the risk of prolapses and incontinence.

Or both influences could be at work.A study of 31,000 people, published in April, linked wider pelvises to easier births, but also slower walking and a greater risk of pelvic floor conditions.

Read moreThe evolution of easier births means slower walking and pelvis issues

The evolution of easier births means slower walking and pelvis issues

There could be even more influences in this dilemma. Betti argues that our pelvises are sensitive tomany factors in the environment, such as temperature. Other researchers have described a “new obstetrical dilemma” linked to rising rates of obesity, which can make babies larger. The real answer is probably some combination of factors, says Betti: she says some researchers have rebranded the dilemma as a “multifactor pelvis”.

Narrower pelvises will affect human health. They will make vaginal childbirth more difficult, potentially leading to even more C-sections. “Who knows how long it will take to get to the state that there will be no children born naturally?” saysRenata Henneberg, part of the team behind the new research and Maciej Henneberg’s wife.

At the same time, narrower pelvises may reduce the risk of pelvic floor problems, which can be very harmful. Childbirth, says Betti, can have “very unpleasant, long-lasting effects, which can affect very negatively the life of a woman”.

However, she says predicting what will happen is difficult, again because so many factors are in play: people are having fewer children, which might reduce the risk of injury, but they are also having them later. “A lot of things have changed at the same time,” she says.

Reference:Research SquareDOI: 10.21203/rs.3.rs-6712615/v1

Research SquareDOI: 10.21203/rs.3.rs-6712615/v1

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The night lizards may have been the only terrestrial vertebrates that survived in the region of the asteroid impact 66 million years ago, which led to the extinction of non-avian dinosaurs

A yellow-spotted tropical night lizard (Lepidophyma flavimaculatum)Dante Fenolio/SCIENCE PHOTO LIBRARY

A yellow-spotted tropical night lizard (Lepidophyma flavimaculatum)

Dante Fenolio/SCIENCE PHOTO LIBRARY

A small, secretive group of lizards that still exists today may have been the only terrestrial vertebrates that survived in the vicinity of theChicxulub asteroid collision, which led to the extinction of the non-avian dinosaurs.

It has long been known that xantusiid night lizards are an ancient lineage that have persisted for tens of millions of years. ButChase Brownsteinat Yale University and his colleagues suspected that the group may have actually arisen earlier than previously thought: in the Cretaceous Period, which ended around 66 million years ago.

Read moreThere’s growing evidence the big five mass extinctions never happened

There’s growing evidence the big five mass extinctions never happened

The end of the Cretaceous was marked by a giant asteroid strike in the vicinity of Yucatán peninsula in Mexico, which left a crater over 150 kilometres wide and caused the extinction of most of the animal and plant species across the world.

Today, the night lizards – a misnomer, as they aren’t actually nocturnal – are still found in Cuba, Central America and the south-west of the US.

Brownstein and his team used previously published DNA sequence data for xantusiids to create an evolutionary tree for the group. They combined this with skeletal anatomy across living and fossil night lizards, allowing the team to determine how old their lineages are and estimate how many offspring the ancestral night lizards would have produced.

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They found that the most recent common ancestor of living xantusiids emerged deep within the Cretaceous, over 93 million years ago, and they probably only had clutches of one or two offspring.

“I think it is very possible that these ancient populations were as close or closer to the impact site than those today,” says Brownstein. “It’s almost as if xantusiid distribution sketches a circle around the impact site.”

Based on fossil evidence, it is unlikely that the ancient night lizards simply recolonised the region later on, says Brownstein.

“We know from our reconstructions that the common ancestor of living species was almost certainly living in North America, where the fossil record of xantusiids is pretty much fairly continuous on either side of the boundary layer marking the impact,” he says.

Read moreThe extraordinary ways species control their own evolutionary fate

The extraordinary ways species control their own evolutionary fate

Many night lizard species live in rock crevices and their slow metabolisms are comparable to those of other survivors of the mass extinction, such as turtles and crocodiles. “This, perhaps, would have allowed them to take shelter during the impact and its immediate aftermath,” says Brownstein.

Nathan Loat the University of Sydney says the lizards are remarkable. “They lived in the region around the asteroid’s point of impact, [yet] they managed to survive, even though the asteroid would have wiped out organisms that were within hundreds of kilometres of the impact point.”

They managed this despite not having many of the usual traits that we would expect to see in survivors of mass extinctions. “The species that tend to survive through these extinction events are those that are small in size, reproduce quickly and that have large geographic ranges,” says Lo. “But these lizards generally reproduce slowly and seem to have quite small ranges.”

Journal reference:Biology LettersDOI: 10.1098/rsbl.2025.0157

Biology LettersDOI: 10.1098/rsbl.2025.0157

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Enigmacursordarted around North America in the Late Jurassic 145-150 million years ago and its skeleton now be on display in London’s Natural History Museum

Illustration ofEnigmacursor mollyborthwickae, a newly recognised dinosaur species© The Trustees of the Natural History Museum, London

Illustration ofEnigmacursor mollyborthwickae, a newly recognised dinosaur species

© The Trustees of the Natural History Museum, London

A newly discovered species of dinosaur is going on display in London’sNatural History Museum.

Enigmacursor mollyborthwickaewas a speedy, two-legged herbivore, 64 centimetres tall and 180 cm long that lived about 145 million to 150 million years ago, during the Late Jurassic Period.

Read moreLargest ever animal may have been Triassic ichthyosaur super-predator

Largest ever animal may have been Triassic ichthyosaur super-predator

Its reconstructed skeleton will be on display in the museum’s Earth Hall from 26 June, alongside its contemporary,Sophie the Stegosaurus.

Susannah MaidmentandPaul Barrett, both palaeontologists at the Natural History Museum, have analysed theEnigmacursorspecimen, which was uncovered from theMorrison Formationin the western US in 2021-22.

Back then, it was thought to be aNanosaurus– a poorly known species of small herbivorous dinosaur. TheEnigmacursorfossil isn’t complete, but using the few teeth – which reveal it ate plants – and portions of the neck, backbone, tail, pelvis, limbs and feet, Maidment and Barrett have defined this fossil as a new species, placed it in an evolutionary tree and reconstructed it for display.

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They have based the structure of missing elements, like the skull, on similar small dinosaurs likeYandusaurusandHexinlusaurus. Generally, we know little about smaller dinosaurs, both because they are less likely to fossilise than bigger animals and because fossil hunters tend to seek larger, more valuable examples.

“This is a two-legged dinosaur and it’s got very small forearms that it probably would have used to grasp food to bring it to its mouth,” says Maidment. “And it’s got incredibly large feet and very long limbs. So, it was probably quite fast by dinosaur standards.”

TheEnigmacursorskeleton at the Natural History Museum in London© The Trustees of the Natural History Museum, London

TheEnigmacursorskeleton at the Natural History Museum in London

© The Trustees of the Natural History Museum, London

That is where the “cursor” part of its name comes from: it means “runner”. Maidment says it was probably charging around in the shadows of behemoths likeDiplodocusandStegosaurus.

The specimen’s vertebrae weren’t fused, which implies it wasn’t fully mature when it died. “I think this animal was probably a teenager, but it may well have been sexually mature, so it might not have got that much bigger,” says Maidment.

Read moreLast common ancestor of all life emerged far earlier than thought

Last common ancestor of all life emerged far earlier than thought

“Enigmacursorrepresents one of the rarities from further down the food chain of the dinosaur era,” saysDavid Normanat the University of Cambridge. “This newly described animal was clearly a small, wallaby-sized herbivore that scampered around the Late Jurassic countryside.”

The discovery sheds light on the early evolutionary stages of the herbivorous dinosaurs that would go on to dominate Cretaceous ecosystems in North America, says Maidment, and helps us build a more realistic ecological picture of the life and times of dinosaurs.

Journal reference:Royal Society Open ScienceDOI: 10.1098/rsos.242195

Royal Society Open ScienceDOI: 10.1098/rsos.242195

Related tourExpeditionDinosaur hunting in the Gobi desert: Mongolia – 1 place remaining16 August 202515 days

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Adults and AI models fail to recognise messages with harmful intent expressed with Gen Alpha slang or memes, raising concerns about youngsters’ online safety

Teenagers’ language might make online bullying hard to detectVitapix/Getty Images

Teenagers’ language might make online bullying hard to detect

Generation Alpha’s internet lingo is mutating faster than teachers, parents andAImodels can keep up – potentially exposing youngsters to bullying and grooming that trusted adults and AI-based safety systems simply can’t see.

Manisha Mehta, a 14-year-old student at Warren E. Hyde Middle School in Cupertino, California, andFausto Giunchigliaat the University of Trento, Italy, collated 100 expressions and phrases popular with Generation Alpha – those born between 2010 and 2025 – from popular gaming,social mediaand video platforms.

Read moreGoogle tool makes AI-generated writing easily detectable

Google tool makes AI-generated writing easily detectable

The pair then asked 24 volunteers aged between 11 and 14, who were Mehta’s classmates, to analyse the phrases alongside context-specific screenshots. The volunteers explained whether they understood the phrases, in what context they were being used and if that use carried any potential safety concerns or harmful interpretations. They also asked parents, professional moderators and four AI models – GPT-4, Claude, Gemini and Llama 3 – to do the same.

“I’ve always been kind of fascinated by Gen Alpha language, because it’s just so unique, the way things become relevant and lose relevancy so fast, and it’s so rapid,” says Mehta.

Among the Generation Alpha volunteers, 98 per cent understood the basic meaning of the terms, 96 per cent understood the context in which they were used and 92 per cent could detect when they were being deployed to cause harm. But the AI models only recognised harmful use in around 4 in 10 cases – ranging from 32.5 per cent for Llama 3 to 42.3 per cent by Claude. Parents and professional moderators were no better, spotting only around a third of harmful uses.

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“I expected a bit more comprehension than we found,” says Mehta. “It was mostly just guesswork on the parents’ side.”

The phrases commonly used by Generation Alpha included some that have double meanings depending on their context. “Let him cook” can be genuine praise in a gaming stream – or a mocking sneer implying someone is talking nonsense. “Kys”, once shorthand for “know yourself”, now reads as “kill yourself” to some. Another phrase that might mask abusive intent is “is it acoustic”, used to ask mockingly if someone is autistic.

“Gen Alpha is very vulnerable online,” says Mehta. “I think it’s really critical that LLMs can at least understand what’s being said, because AI is going to be more prevalent in the field of content moderation, more and more so in the future.”

“It’s very clear that LLMs are changing the world,” says Giunchiglia. “This is really paradigmatic. I think there are fundamental questions that need to be asked.”

The findings were presented this week at the Association for Computing Machinery Conference on Fairness, Accountability and Transparency in Athens, Greece.

“Empirically, this work indicates what are likely to be big deficiencies in content moderation systems for analysing and protecting younger people in particular,” saysMichael Vealeat University College London. “Companies and regulators will likely need to pay close attention and react to this to remain above the law in the growing number of jurisdictions with platform laws aimed at protecting younger people.”

Reference:FAccT ’25: Proceedings of the 2025 ACM Conference on Fairness, Accountability, and TransparencyDOI: 10.1145/3715275.3732184

FAccT ’25: Proceedings of the 2025 ACM Conference on Fairness, Accountability, and TransparencyDOI: 10.1145/3715275.3732184

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Since 1970, heart attack deaths have fallen almost 90 per cent in the US, though deaths from chronic heart conditions have significantly risen

Bystander CPR training may have contributed to fewer heart attack deaths in the past five decadespiyamas dulmunsumphun / Alamy Stock Photo

Bystander CPR training may have contributed to fewer heart attack deaths in the past five decades

piyamas dulmunsumphun / Alamy Stock Photo

Deaths fromheart attackshave plummeted in the US over the past 50 years, whereas deaths from chronic heart conditions have skyrocketed, probably due to people living longer.

“We’ve made some really great progress in certain areas of heart disease mortality, but now we’re seeing this shift,” saysSara Kingat Stanford University in California.

Read moreThe radical treatments bringing people back from the brink of death

The radical treatments bringing people back from the brink of death

She and her colleagues collected data on heart disease deaths from 1970 to 2022 using the US Centers for Disease Control and Prevention’s WONDER database, which tracks all recorded fatalities in the country.

They found that in 2022, heart disease accounted for 24 per cent of all deaths in the US, down from 41 per cent in 1970. The decline is largely thanks to an almost 90 per cent decrease in heart attack deaths, which were once the deadliest form of heart disease.

“Incredible progress has been made to reduce deaths from heart attacks over the last 50 years,” says King. This includesnew therapiessuch as heart stents, coronary artery bypass surgery and cholesterol-lowering medications. Public health measures, such as bystander CPR training and efforts to lower smoking rates, have also probably helped, says King.

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Even so, heart disease remains the country’s top killer, mainly because deaths from other types of heart disease – mostly chronic conditions – have increased 81 per cent over the same period. For instance, fatalities from heart failure, arrhythmia and hypertensive heart disease have risen 146 per cent, 106 per cent and 450 per cent, respectively.

“A lot of these conditions are conditions that come with age,” says King. “To us, it seems like people that are now surviving these heart attacks are living longer and having more time to sort of develop these chronic heart conditions.”

Read moreThe surprising truth about the health benefits of snacking

The surprising truth about the health benefits of snacking

However, the data may exaggerate the shift in heart disease deaths. “There are a lot of different causes that could lead to somebody’s death, and that can lead to misclassification or oversimplification,” says King. For instance, many people die from heart failure after havingsurvived a heart attack. “The underlying cause of that heart failure is still the blockages in those coronary arteries, so it isn’t black and white,” says King.

Still, the majority of heart disease deaths are clearly no longer due to heart attacks. “It is going to be important that we focus on these other rising causes of mortality,” says King. “Finding ways to age healthily will be the next frontier in cardiology.”

Journal reference:Journal of the American Heart AssociationDOI: 10.1161/JAHA.124.038644

Journal of the American Heart AssociationDOI: 10.1161/JAHA.124.038644

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Cancer cells can acquire energy-generating structures called mitochondria from nearby nerve cells, which seems to aid their spread, a discovery that could lead to new treatments

A nerve cell (stained green) growing among a cancer cell cultureSimon Grelet and Gustavo Ayala

A nerve cell (stained green) growing among a cancer cell culture

Cancercells steal energy-generating parts from nerve cells to fuel their spread to distant sites, a discovery that could improve treatments against the deadliest tumours.

“This is the first time that mitochondrial exchange has been demonstrated from nerves to cancer cells,” saysElizabeth Repaskyat the Roswell Park Comprehensive Cancer Center in Buffalo, New York, who wasn’t involved in the research. “It’s a major next step in cancer neuroscience, a field that’s exploding.”

Read moreThe chilling discovery that nerve cells help cancers grow and spread

The chilling discovery that nerve cells help cancers grow and spread

We already knew that nerve cells, or neurons, within and surrounding tumours produce proteins and electrical signals that help cancer grow and spread. “Cancers with higher nerve density are associated with poorer prognosis,” saysSimon Greletat the University of South Alabama.

Prior studies have also shown that brain cancer cells can acquire mitochondria – energy-generating structures – from non-neuronal brain cells. But it was unknown whether tumour cells could take mitochondria from nerve cells, says Grelet.

To find out, he and his colleagues genetically engineered breast cancer cells from mice to contain a red fluorescent molecule and mixed them with mouse nerve cells, containing mitochondria labelled with green pigment, in a lab dish. By imaging the cells, they found that cancer cells stole mitochondria from the nerve cells within a few hours.

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“The cancer cells elongate their membrane so they are stealing, siphoning, the mitochondria from the neurons,” says Grelet. “It’s like a train of mitochondria that pass through a very tiny structure, entering the cancer cell one at a time,” he says.

To see if this occurs in the body, the researchers injected red breast cancer cells into the nipples of female mice to form tumours. They also genetically engineered the nerves around the tumours to carry green mitochondria. Around a month later, 2 per cent of the cancer cells in these tumours had acquired mitochondria from neurons.

In contrast, 14 per cent of tumour cells that had spread to the brain carried nerve-derived mitochondria – suggesting that cancer cells with nerve-derived mitochondria were much better at spreading than those without. Further experiments suggest this is because cells with stolen mitochondria are better at enduring physical and chemical stresses that they encounter in the bloodstream.

“There are many, many obstacles for a cancer cell that’s trying to spread,” says Repasky. “They have to break out of the initial tumour, make it through barriers of the blood vessels, get out of the blood, then get enough oxygen and nutrients at the secondary site – most of them don’t make it,” she says. “Stealing mitochondria seems to allow cancer cells to better endure that obstacle course,” she says.

Read moremRNA cancer therapy now in human trials after shrinking mouse tumours

mRNA cancer therapy now in human trials after shrinking mouse tumours

To explore if this happens in people, the researchers analysed tumour samples from eight women with breast cancer that had spread to distant sites within their bodies. They found that tumour cells from other parts of the body had 17 per cent more mitochondria, on average, compared with those in the breast, suggesting the process does occur in patients, says Grelet.

What’s more, the team analysed a human prostate tumour sample and found that cancer cells closer to nerves contained substantially more mitochondria than those further away. “We think it would be a universal mechanism that all sorts of tumours will be doing,” says team memberGustavo Ayalaat the University of Texas Health Sciences Center at Houston.

The findings suggest that blocking mitochondrial transfer could reduce the spread of the deadliest tumours. “I do believe this will be possible, at least in certain kinds of tumours,” says Repasky. Ayala says the researchers plan to develop drugs that can do this.

Journal reference:NatureDOI: 10.1038/s41586-025-09176-8

NatureDOI: 10.1038/s41586-025-09176-8

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Mice created using genetic material from two sperm cells have gone on to have offspring off their own, but the prospect of one day using the technique in humans has potential to cause controversy

“All hell will break loose, politically and morally, all over the world.” So said James Watson, the Nobel prize-winning co-discoverer of DNA’s double helix, on the possibility of human in vitro fertilisation in 1974. Four years later, Louise Brown, the first successful IVF baby, was born.

Today, more than 12 million people have been conceived via IVF, and hell seems still to be broadly contained. Few of us would bat an eye at the procedure.

But what of our attitudes to future reproductive technology? That question is raised by the birth offertile mice with two genetic fathers. Such featshave been attempted before, creating both motherless and fatherless mice, but this latest technique stands apart because it doesn’t involve genetic modification. In principle, that makes it suitable for use in humans.

There are many technical reasons why this won’t happen soon, from the low success rate to the large number of human eggs, stripped of their DNA, that would be required. Despite that, we should start thinking about the social hurdles.

For some people, the thought of a child with two genetic fathers will never be acceptable, just as there are still those who decry gay couples adopting a family. Such minds will be difficult, if not impossible, to change.

As with IVF, what was once front-page news could become run of the mill

As with IVF, what was once front-page news could become run of the mill

But we can expect a broader group of people to have, if not strict moral objections to the idea, a general unease. The first children born in this way, if any are, will, in a way, be unlike any humans that have ever existed. While IVF children are conceived via a process our ancestors could never imagine, they still continue a genetic lineage of every person having one male progenitor and one female.

Does this matter? Quite possibly not – as with IVF, what was once front-page news could become run of the mill. But in an era when the US iscurtailing reproductive and transgender rights, having an open discussion about the technology without prejudice will be the bigger challenge. It is perhaps fortunate that these questions don’t have to be settled any time soon.

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Weight-loss surgery seems to lower the risk of colorectal cancer by changing where bile acids enter the small intestine, raising the possibility of developing treatments that mimic these effects

Gastric bypass surgery is generally used for weight loss, but it may have other benefitsPortra/Getty Images

Gastric bypass surgery is generally used for weight loss, but it may have other benefits

A common form of weight-loss surgery may cut the risk of colorectalcancerby altering levels of molecules called bile acids in the blood and small intestine. The findings could lead to new treatments forbowel cancer.

Gastric bypass surgery involves stapling the stomach to form a small upper pouch and a larger lower pouch. The small intestine is then connected to the upper pouch so food and digestive juices bypass most of the stomach and the start of the small intestine. After having the surgery, people typically feel full sooner and lose weight.

Read moreThe alarming rise of colorectal cancer diagnoses in people under 50

The alarming rise of colorectal cancer diagnoses in people under 50

Prior studies have also linked the procedure to areduced risk of colorectal cancer, but it was unclear why. To find out,Rebecca Kesselringat the University of Freiburg in Germany and her colleagues fed mice a high-fat diet until they gained around 50 per cent of their initial body weight, on average. They then gave a third of the mice gastric bypass surgery while the rest underwent sham surgery that didn’t rearrange their digestive organs.

Aiming to isolate the effect of having gastric bypass surgery from that of losing weight, the team put the gastric bypass group and half of the remaining mice on a diet that caused them to lose about a fifth of their weight, on average, over six weeks.

The researchers then implanted colorectal cancer cells into the mice’s colons. After another six weeks, they found that colon tumours in the gastric bypass group were two-thirds smaller than those of either the mice that had kept gaining weight or the mice that had lost weight through diet alone.

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What’s more, tumours had spread to the liver in only one mouse out of 20 in the gastric bypass group, while this occurred in most animals in the sham groups.

“As both sham groups had similar tumour levels but different weights, weight loss itself didn’t account for the reduced cancer risk – there was something else about bypass surgery,” says Kesselring.

The team wondered if changes in bile acids, a mix of molecules that digest fats, might be responsible. These are usually made by the liver and pass through the gall bladder, stomach and small intestine before returning to the liver via the blood.

“With bypass surgery, bile acids are introduced later into the small intestine,” says Kesselring. This means they may encounter a different mix of gut bacteria, which chemically alter the molecules.

The mice that underwent gastric bypass surgery had reduced levels of some bile acids called primary bile acids in their colons and blood compared with those in the sham groups.

Read moreBeyond Wegovy: Could the next wave of weight-loss drugs end obesity?

Beyond Wegovy: Could the next wave of weight-loss drugs end obesity?

To test whether bile acid changes really did alter cancer risk, the team put another group of mice through the same experiment – but instead of gastric bypass surgery, these mice had an operation that simply diverted their bile acids to a later part of their small intestine without altering the stomach.

Crucially, the team found that this lowered levels of primary bile acids in the blood and reduced the size and spread of colorectal tumours in these mice as effectively as gastric bypass surgery. This was supported by another experiment where the team found that primary bile acids boost the growth of colorectal cancer cells in a lab dish.

The findings suggest that targeting primary bile acids could help treat cancer. “We could maybe figure out some oral drug that reduces these bile acids, that we could give to people with cancer, to simulate some of these beneficial effects of [gastric bypass] surgery,” saysVance Albaughat Louisiana State University.

Journal reference:Science Translational MedicineDOI: 10.1126/scitranslmed.ads9705

Science Translational MedicineDOI: 10.1126/scitranslmed.ads9705

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