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<p>Men’s average testosterone levels have halved over the past 50 years, according to scientists who say society is facing a male fertility crisis. Rising levels of obesity and diabetes are expected to play a part, but the team behind the work suggest that environmental factors such as endocrine-disrupting chemicals – which can be found in various household items – and global heating could also be factors in the apparent striking decline. Ian Sample speaks to science correspondent Hannah Devlin to find out how the work has been received and what the researchers want to see happen in response to their finding</p><p><strong><a href="https://www.theguardian.com/society/2026/jul/07/mens-average-testosterone-levels-have-halved-in-last-50-years-say-scientists">Men’s average testosterone levels have halved in last 50 years, say scientists</a></strong></p><p>Support the Guardian: <a href="http://theguardian.com/sciencepod">theguardian.com/sciencepod</a></p> <a href="https://www.theguardian.com/science/audio/2026/jul/09/is-male-testosterone-in-freefall-podcast">Continue reading...</a>

<p>‘Persistent’ inequities found to exist in access to prevention, diagnosis, treatment and care, annual global review says </p><p>Remarkable scientific progress against cancer has changed very little for millions of patients globally, who face devastating physical, emotional and financial consequences after diagnosis, a new World Health Organization report has warned.</p><p>One person in five will develop cancer, according to WHO estimates, and the disease will touch 92% of people, either through their own diagnosis or that of a close family member.</p> <a href="https://www.theguardian.com/global-development/2026/jul/08/health-who-global-persistent-inequities-progress-cancer-prevention-diagnosis-treatment-care">Continue reading...</a>

<p>Modern forensic analysis leads to arrest in murder of traveling salesman John Warren, authorities say</p><p>Items that were found discarded behind a Cracker Barrel restaurant in <a href="https://www.theguardian.com/us-news/state-of-georgia">Georgia</a> in 1985 have led to charges against a suspect in an <a href="https://www.theguardian.com/us-news/ohio">Ohio</a> killing committed at about that time, investigators announced recently.</p><p>As told by authorities, the case centering on killed traveling salesman John Warren is among the latest in the US criminal justice system to illustrate how the application of modern forensic testing techniques on evidence collected decades earlier can lead to closure of cold murder cases.</p> <a href="https://www.theguardian.com/us-news/2026/jul/08/modern-forensic-evidence-1985-georgia-murder">Continue reading...</a>

<p>I can’t blame my patients for turning to its straightforward assessments. But it has real risks – and care may require human messiness</p><p>“Chat told me I should break up with him.”</p><p>I instructed my face to remain therapist-neutral, but I must have smirked. The truth is, I was annoyed. We had been discussing the viability of this relationship for weeks, and in an instant AI had brought the answer. “How do you feel about it?” She said this had been her gut feeling all along. The following session, her relationship was over.</p> <a href="https://www.theguardian.com/commentisfree/2026/jul/08/chatgpt-ai-therapy">Continue reading...</a>

<p>Exclusive: Researchers warn of ‘major crisis in male reproductive health’ partly driven by obesity and diabetes</p><p>Men’s average testosterone levels have halved over the past 50 years, according to scientists who say that society is facing a male fertility crisis.</p><p>Total testosterone levels in men declined by 54% between 1972 and 2019, according to data presented at the annual meeting of the European Society of Human Reproduction and Embryology in London on Tuesday.</p> <a href="https://www.theguardian.com/society/2026/jul/07/mens-average-testosterone-levels-have-halved-in-last-50-years-say-scientists">Continue reading...</a>

<p>Researchers testing a cheap, homegrown oil in Uganda found what cats knew all along – it worked as well as the artificial chemical used globally </p><p>A homegrown catnip lotion has proven “just as effective as Deet” as a mosquito repellant in trials carried out in Uganda.</p><p>Catnip, or <em>Nepeta cataria</em>, is a common herb from the mint family. The chemical in the plant that causes feline euphoria – nepetalactone – also has insect-repelling properties but this has not previously been commercialised.</p> <a href="https://www.theguardian.com/global-development/2026/jul/07/catnip-lotion-as-effective-as-deet-at-repelling-mosquitoes-study-finds">Continue reading...</a>

<p>In the last 50 years, Britain has lost an astonishing 73 million wild birds from its landscape, according to the British Trust for Ornithology. Habitat loss, pesticides, disease, cats and the climate crisis mean there are fewer birds than ever before. For children and young people it can be difficult to appreciate the scale of the loss due to a psychological phenomenon called ‘shifting baseline syndrome’, where each generation inherits a degraded version of the environment, and therefore doesn’t notice the overall decline. But Gen Z are bucking the trend. Thanks to social media and the Merlin Bird ID app, birding has become cool. To find out what we’re missing from the dawn chorus, and why <a href="https://www.theguardian.com/environment/2026/may/01/birdwatching-boom-britain-nature-gen-z-rspb-environment">young people are embracing birdwatching</a>, Madeleine Finlay hears from the writer Robert Macfarlane and from Jess Painter, a member of the RSPB’s youth council</p><p><strong><a href="https://www.theguardian.com/environment/2026/jul/03/dawn-chorus-uk-birdsong-50-years-audio-landscape">Listen to Britain’s dawn chorus of 1976: the dramatic loss of birdsong in 50 years</a></strong></p><p><strong><a href="https://guardianbookshop.com/the-book-of-birds-9780241404737/">To support the Guardian order The Book of Birds from Guardian Bookshop</a></strong></p> <a href="https://www.theguardian.com/science/audio/2026/jul/07/a-break-from-scrolling-how-gen-z-fell-in-love-with-birding-podcast">Continue reading...</a>

<p>Study of more than 2,000 men identifies epigenetic changes linked to exposure to common outdoor pollutants</p><p>Air pollution appears to alter how sperm genes function, one of the largest fertility studies of its kind has found.</p><p>Men exposed to common air pollutants while sperm were developing showed subtle DNA changes that affected whether genes were switched on or off, raising fresh concerns air pollution may harm male fertility.</p> <a href="https://www.theguardian.com/science/2026/jul/07/air-pollution-dna-changes-sperm-men">Continue reading...</a>

<p>The answer to today’s puzzle</p><p>Earlier today I set you this puzzle about an imaginary game show.</p><p>At the end of the show two people will be chosen and each placed in a separate booth.</p> <a href="https://www.theguardian.com/science/2026/jul/06/did-you-solve-it-this-tv-show-is-flipping-brilliant">Continue reading...</a>

<p>As the Smithsonian’s National Air and Space Museum turns 50, an expansive exhibition celebrates how art has coincided with space</p><p>Wearing a shiny silver spacesuit, Alan Shepard clutches his helmet and looks like an archetypal blue-eyed American hero. The <a href="https://npg.si.edu/object/npg_61.6">1961 portrait by Bruce Stevenson</a> paid tribute to the first US astronaut in space. It also planted a seed.</p><p>James Webb, the then administrator of Nasa, saw the painting and was inspired to start the space agency’s own art programme, believing that artists could bring a unique perspective to exploring the cosmos. From 1962 to 1974 it was led by <a href="https://www.nasa.gov/get-involved/art-program/a-different-perspective-remembering-james-dean-founder-of-the-nasa-art-program/">James Dean</a>, who then became the first art curator at the <a href="https://www.si.edu/museums/air-and-space-museum">Smithsonian National Air and Space Museum</a> in Washington.</p> <a href="https://www.theguardian.com/artanddesign/2026/jul/06/smithsonian-space-museum-exhibition">Continue reading...</a>

<p>A probability puzzle</p><p>Today’s puzzle imagines a TV game show.</p><p>The compere announces that at the end of the show two people will be chosen and each placed in a separate booth.</p> <a href="https://www.theguardian.com/science/2026/jul/06/can-you-solve-it-this-tv-show-is-flipping-brilliant">Continue reading...</a>

<p>Organisation says objects consistent with ‘debris from a foreign rocket body that recently re-entered the atmosphere’ </p><p>The Australian Space Agency has said the six so-called “space balls” <a href="https://www.theguardian.com/australia-news/2026/jul/05/mysterious-debris-found-on-queensland-beaches-could-be-space-balls-and-may-contain-toxic-rocket-fuel">found in north Queensland</a> were likely from a “foreign rocket body” that had recently re-entered the atmosphere after being in orbit.</p><p>The six mysterious objects were found by the public washed ashore in the Forrest Beach area, north of Townsville, on Friday, Saturday and Sunday and were suspected of containing hazardous chemicals.</p> <a href="https://www.theguardian.com/australia-news/2026/jul/06/mysterious-space-balls-queensland-beaches-origin-source-australia">Continue reading...</a>

<p>Cluster might look like a mini version of the Plough unless you grab your binoculars</p><p>In the early hours of 11 July, the waning crescent moon will be gliding past the beautiful Pleiades star cluster, which is also known as M45 or the Seven Sisters.</p><p>The chart shows the view looking east-north-east from London at 3am BST. By then, the sky will getting ready to start brightening for the coming day, so a clear, low horizon will be essential to see the pairing.</p> <a href="https://www.theguardian.com/science/2026/jul/06/starwatch-waning-crescent-moon-pairs-up-with-the-seven-sisters">Continue reading...</a>

<p>Study finds those who speak two languages have brains that appear around six years younger than those who speak one</p><p>Learning another language could slow ageing in the brain by up to 13 years, according to research.</p><p>People who speak more than one language seem to have younger brains and the more languages you speak and the earlier you speak them, the better, according to findings from a study being presented at the Federation of European Neuroscience Societies conference in Barcelona.</p> <a href="https://www.theguardian.com/education/2026/jul/06/learning-another-language-appears-to-slow-brain-ageing-scientists-say">Continue reading...</a>

<p>Polling shows that the public supports this new technology, but the conversation must move beyond simple questions of safety</p><p>Ever since Crispr-Cas9 gene-editing technology emerged in the early 2010s, ethical questions around genetically altered humans, so-called designer babies, have become increasingly urgent. There is already a worldwide legal prohibition. No country currently allows human germline editing (meaning genetic changes to an embryo that could also be passed on to its children), and <a href="https://academic.oup.com/jlb/article/12/1/lsaf007/8129080">70 have laws against it</a>, including the UK. But a series of recent discoveries and a new poll suggest that scientists and the public believe gene-edited humans are likely – even desirable – in the near future.</p><p>Two new studies use base editing – a more precise next-generation Crispr tool – on human embryos to study early development or disease (this research is legal in the UK and US as long as the embryos are destroyed within 14 days). The lead author of one study, Dieter Egli, <a href="https://www.cuimc.columbia.edu/news/study-identifies-pitfall-correcting-mutations-human-embryos-crispr">said that</a> the technology wasn’t yet ready for the clinic, but the advances would “guide responsible research to achieve its ultimate safe and effective use”. This encapsulates the view of many scientists, who believe the regulated use of germline editing to eradicate hereditary conditions is inevitable, and the main objection is around safety.</p> <a href="https://www.theguardian.com/commentisfree/2026/jul/05/the-guardian-view-on-gene-edited-humans-darker-uses-must-be-acknowledged-alongside-medical-ones">Continue reading...</a>

<p>Humans have long sought to geoengineer the Earth’s environment. <strong>Tim Flannery</strong> outlines a few of the wildest ideas from the 20th century</p><p>An increasing number of scientists think we have let the climate crisis fester for so long that our only hope to stave off ever-intensifying catastrophes is to use technological interventions. Cloud brightening, injecting sulphur into the atmosphere and the use of tiny mirrors in space – all of which might reduce the amount of sunlight reaching Earth’s surface – are among the concepts being promoted<strong> </strong>by entrepreneurs and governments alike. Geoengineering, they argue, is now inevitable.</p><p>Ever since the God of the Old Testament granted our species dominion over the Earth, ideas of remaking the world to better suit us have been a dominant thread in human thinking. We have for centuries toyed with grand ambitions to alter and re-form the climate and environment, many of which – in retrospect – seem doomed or absurd.</p><p><strong><a href="https://www.theguardian.com/australia-news/2021/dec/21/sign-up-for-five-great-reads-guardian-australias-wrap-of-our-best-summer-stories">Sign up for a weekly email featuring our best reads</a></strong></p> <a href="https://www.theguardian.com/environment/2026/jul/06/five-outlandish-plans-to-remodel-earth-climate">Continue reading...</a>

<p>Finding that Norfolk butterfly has been distinct subspecies for 200,000 years could transform conservation approach</p><p>The endangered swallowtail butterfly <em>Papilio machaon britannicus</em>, which is only regularly found breeding in Britain on the Norfolk Broads, has been a distinct subspecies for at least 200,000 years, according to a study.</p><p>Smaller, darker in colour and much rarer than the continental swallowtail, <em>britannicus</em> was previously considered to have developed its distinctive form during its confinement in the wetlands of eastern England over the last 8,000 years, after the flooding of Doggerland.</p> <a href="https://www.theguardian.com/environment/2026/jul/05/british-swallowtail-butterfly-distinct-subspecies-study-conservation">Continue reading...</a>

<p>Australian Space Agency working to confirm origin of objects as space archaeologist says they may be connected to a rocket launch</p><p>Six pieces of suspected space debris found washed up on north Queensland beaches could be “space balls” that are often left over from rocket launches, according to one expert.</p><p>The Australian Space Agency confirmed on Sunday it was working to determine the nature and origin of the mysterious objects which police said were suspected of containing hazardous chemicals.</p> <a href="https://www.theguardian.com/australia-news/2026/jul/05/mysterious-debris-found-on-queensland-beaches-could-be-space-balls-and-may-contain-toxic-rocket-fuel">Continue reading...</a>

<p>As this year’s invertebrate of the year competition launches, we join scientists studying last year’s winner</p><ul><li><p><a href="https://www.theguardian.com/environment/2026/jul/01/nominate-your-invertebrate-of-the-year">Nominate your invertebrate of the year</a></p></li></ul><p>Witek Morek is closely inspecting an old brick-and-flint wall on the Cambridgeshire campus of the Wellcome Sanger Institute.</p><p>“We are going to use a very advanced tool designed by bioengineers and evolved over millions of years – the human hand – and grab some moss, and put it in an envelope,” he says.</p> <a href="https://www.theguardian.com/environment/2026/jul/04/hunting-tardigrade-sequencing-dna-life-earth-invertebrate-year">Continue reading...</a>

<p>Study suggests even light activity such as ironing could reduce health risks linked to prolonged sedentary behaviour</p><p>Sitting for longer than half an hour at a time each day raises the risk of dying from cancer, a study suggests.</p><p>Researchers who tracked more than 90,000 people over a decade found that sitting or lying down while awake for more than 30 minutes in one period each day was associated with an increased risk of cancer death. The risk increases for every additional hour of continuous inactivity, the findings suggest.</p> <a href="https://www.theguardian.com/science/2026/jul/02/sitting-minutes-cancer-death-risk-study">Continue reading...</a>

<p>Differences in unhealthy cholesterol levels and blood pressure found to have ‘narrowed or disappeared’ in over-40s</p><p>Many adults living with obesity have “indistinguishable” cholesterol and blood pressure levels compared with those who are a healthy weight, largely because of the use of statins, according to a study.</p><p>In some cases, people with obesity were “better off” than those of a healthy weight, researchers added.</p> <a href="https://www.theguardian.com/society/2026/jul/02/over-40s-obesity-normal-bmi-cholesterol-blood-pressure-study-finds">Continue reading...</a>

<p>Researchers claim they are closer to creating life from nothing after building tiny, quivering blobs that use lab-made DNA to feed, grow and multiply in a dish. To find out how significant this step is, and where scientists hope it will lead, Madeleine Finlay hears from co-host Ian Sample and from Kate Adamala, professor of genetics at the University of Minnesota</p><p><strong><a href="https://www.youtube.com/@ItsComplicated">Follow It’s Complicated on YouTube</a></strong></p><p>Support the Guardian: <a href="http://theguardian.com/sciencepod">theguardian.com/sciencepod</a></p> <a href="https://www.theguardian.com/science/audio/2026/jul/02/beautiful-blobs-can-scientists-build-life-from-scratch-podcast">Continue reading...</a>

<p>Tiny, quivering spheres designed to feed and multiply raise prospect of artificial organisms to make drugs, food and fuel</p><p>Researchers claim they are closer to creating life from scratch after building tiny, quivering blobs that use lab-made DNA to feed, grow and multiply in a dish.</p><p>The synthetic cells were made from chemical compounds and are believed to be the first to demonstrate the complete cell cycle of growth, genetic replication and splitting to produce the next generation.</p> <a href="https://www.theguardian.com/science/2026/jul/01/synthetic-life-lab-made-dna-spudcells-scientists">Continue reading...</a>

<p>Some adults aged 65 and above will be able to get the drug for $50 through Medicare GLP-1, a temporary program</p><p>Kathryn, a retiree who worked in healthcare, has throughout her life experienced “cyclical weight-loss, weight-gain”.</p><p>“Every time that that has happened, it’s been a little bit greater of the loss and the gain, which is really unhealthy,” said the 66-year-old who lives in Denver, Colorado, and requested that only her first name be used. At her heaviest, the 5ft 1in-woman weighed 220lbs.</p> <a href="https://www.theguardian.com/us-news/2026/jul/01/medicare-glp1-pilot-program">Continue reading...</a>

<p>Final vowel in words such as happy, baby and chilly varies clearly by social class across the city </p><p>Pronunciation of the “happy vowel” is one of the key indicators of social class in Mancunian accents, researchers have found.</p><p>A sociolinguistic study, led by Lancaster University, found that the final vowel in words such as happy, baby, chilly and city – known to linguists as “the happy vowel” – varies clearly by social class across Manchester.</p> <a href="https://www.theguardian.com/uk-news/2026/jul/01/happy-vowel-key-indicator-social-class-manchester-accents-study">Continue reading...</a>