As world leaders began to gather at Cop27 yesterday, speeches began on the main stage in Sharm el-Sheik. Presidents and prime ministers spoke of the need to rapidly reduce carbon emissions and the horrendous impacts of climate breakdown. But, if previous years are anything to go by – these words may not turn into concrete actions. Instead, indigenous and community groups are leading the charge on saving the planet. Madeleine Finlay speaks to Nina Lakhani about the need for climate justice, and hears from activist Nonhle Mbuthuma about her fight to protect South Africa’s Wild Coast. Help support our independent journalism at theguardian.com/sciencepod

On Sunday, world leaders, negotiators and industry representatives will begin to arrive in Sharm el-Sheik in Egypt for Cop27, the UN’s climate change conference. A UN report set the stage for talks last week, stating that there is “no credible pathway to 1.5C in place” and that progress on limiting global temperature rises has been “woefully inadequate”. So will governments take the opportunity to press ahead with their promises or could the conference live up to accusations of greenwashing? In the first of five special episodes covering Cop27, Madeleine Finlay hears from Guardian Australia’s climate and environment editor Adam Morton about what’s happened since Cop26, our current path to catastrophic heating and what’s likely to be on the agenda over the next two weeks. Help support our independent journalism at theguardian.com/sciencepod

A new trial is exploring if prescriptions of surfing, gardening and dance classes can reduce anxiety and depression in people aged 11 to 18. NHS mental health trusts in 10 parts of England will use a range of sports, arts and outdoor activities with 600 young people to see if it can stop conditions worsening while the sufferers are on waiting lists for care. This kind of support is known as ‘social prescribing’, allowing health professionals to refer patients to a range of community groups and organisations. But while social prescribing programmes are being rolled out around the world, a recent review has found scant evidence of their effectiveness. Madeleine Finlay speaks to Prof Susan Smith about the ideas behind social prescribing, its potential benefits for those with complex issues, and why more studies are urgently needed. Help support our independent journalism at theguardian.com/sciencepod

Crushed by a cart, infected with parasitic worms and painful bunions caused by pointy shoes. These might sound like curses you’d wish on your worst enemy, but a group of researchers have discovered they were probably a part of normal life in medieval Cambridge. Across several archaeological sites, the team have excavated and analysed hundreds of bones to uncover the accidents and afflictions of people in the middle ages. In this Halloween special, Madeleine Finlay hears from Nicola Davis as she takes a trip to Cambridge to investigate what old skeletons can reveal about the lives of those in centuries gone by. Help support our independent journalism at theguardian.com/sciencepod

Researchers have successfully transplanted human neurons into the brains of rats. The recent, groundbreaking study described how the human cells took root inside the rat brains, hooked up to their blood supplies and tapped into neural circuitry. Rather than create a kind of super-rat, the ultimate aim is to better understand neuropsychiatric disorders such as epilepsy and schizophrenia, and examine the effects of drugs in real time. But do the potential benefits outweigh the ethical questions that come with combining human cells with other animals? Ian Sample speaks to Prof Julian Savulescu about how the scientists managed to transplant the neurons, what this means, and how we decide where to draw the line in such an ethically complex field of research. Help support our independent journalism at theguardian.com/sciencepod

Last week, a scientific assessment found wildlife populations have plunged by an average of 69% in just under 50 years. Such rapid and significant losses are leaving many of us with a deep sense of grief and anxiety. To make sense of these emotions and channel them into action, people are increasingly performing rituals and commemorative acts for the natural world. Madeleine Finlay speaks to Prof Claire White about the power of rituals in bringing us together to process grief, and hears from author Andri Magnason about why he wrote a eulogy for Okjökull, the first Icelandic glacier officially lost to the climate crisis. Help support our independent journalism at theguardian.com/sciencepod

Dr Paul McCrory is a world-renowned concussion expert whose work shaped concussion policy across global sport for the past 20 years. In his work, and through his role on the influential Concussion in Sport Group, McCrory had previously adopted a sceptical view on the link between concussions and chronic traumatic encephalopathy (CTE) – a progressive brain condition whose symptoms are similar to Alzheimer’s disease. Last week, the British Journal of Sports Medicine (BJSM) retracted nine of his articles and attached an ‘expression of concern’ to another 74. In an editorial, the BJSM, and its publisher, BMJ, stated that ‘their trust in McCrory’s work –specifically the articles that he has published as a single author – is broken’. Ian Sample speaks to senior sports writer Andy Bull about how the scandal unfolded, what it could mean for players and what is likely to happen next. Help support our independent journalism at theguardian.com/sciencepod

Plastic pollution is damaging the health of the environment, wildlife and us. It has been found on remote islands, in Antarctic snow and in human blood, breast milk and lungs. Alongside rapidly reducing how much plastic we produce, we also need to find new ways to tackle the waste we have created. Madeleine Finlay speaks to the Guardian’s environment editor, Damian Carrington, about the discovery of an enzyme that can rapidly break down plastic bags – found inside the saliva of wax worms – and where else we might find solutions in the natural world. Help support our independent journalism at theguardian.com/sciencepod

Back in April this year, Tesla chief executive Elon Musk signed a $44bn (£40bn) takeover agreement for Twitter. But, in July, the world’s richest man said he was walking away from the controversial deal, arguing Twitter has more spam accounts than it claims. Then, last week, Musk offered to complete the acquisition in a dramatic U-turn. So what might happen next? Ian Sample talks to the Guardian’s global technology editor, Dan Milmo, about why Musk wants to own the social media platform, hears about the twists and turns of the saga so far, and finds out if the takeover is ever likely to happen. Help support our independent journalism at theguardian.com/sciencepod

On 13 September Mahsa Amini, a 22-year-old Kurdish woman, was arrested in Tehran for allegedly violating Iran’s hijab rules. Three days later she was dead. Since then, videos of anti-regime demonstrations and acts of resistance have gone viral – leading the government to block internet access in parts of Tehran and Kurdistan. Madeleine Finlay speaks to Azadeh Akbari about why Mahsa Amini’s death has sparked so much anger, and hears from Alp Toker about how governments and regimes around the world are able to limit internet access.. Help support our independent journalism at theguardian.com/sciencepod