CrowdScience

In many languages across the world, all nouns are classed as either male or female, or sometimes neuter. The English language, however, only signals gender in its pronouns - he, she, it or they. For inanimate objects, gender just crops up in occasional examples like ships or countries, which, for some reason, are deemed female. This lack of gender in English intrigued CrowdScience listener Stuart, since the other languages he knows all highlight whether something is male or female. Did English ever have gender, and if so, where did it go? Presenter Anand Jagatia dives into some Old English texts to uncover the idiosyncrasies of its masculine and feminine nouns, and learns why these gradually fell out of use. But why do other languages assign gender to nouns – male, female, and sometimes many more categories too? And does this affect the way we think? Contributors: Andrew Dunning, Curator of Medieval Manuscripts, Bodleian Library, Oxford University Rachel Burns, Departmental Lecturer in Old English, Oxford University Suzanne Romaine, Professor of Linguistics, Hawaii Ida Hadjivayanis, Senior Lecturer in Swahili, SOAS University Angeliki Alvanoudi, Sociolinguist, Aristotle University of Thessaloniki Amy Bahulekar, Writer, Mumbai Presenter: Anand Jagatia Producer: Eloise Stevens Editor: Cathy Edwards Production: Ishmael Soriano

Buildings inspire many emotions, like awe, serenity or even dread. CrowdScience listener Siobhan was struck by this as she passed a huge apartment block with tiny windows; it reminded her of a prison. So, she asked us to investigate the feelings that buildings can trigger. Architects have long considered how the effect of buildings on their occupants or passersby: asking whether certain features elicit feelings of wonder or joy... or sadness and fear. And now modern neuroscience has started to interrogate these very questions, too. How much of the way we feel about a building is to do with its intrinsic design, and how much is due to our individual brain chemistry and life experiences? Presenter Caroline Steel talks to designer Thomas Heatherwick about his ideas for improving public spaces; enters a virtual reality simulation in Denmark to learn about the emerging field of ‘neuroarchitecture’; and finds out why people just can’t agree what makes a ‘good’ or ‘bad’ building. Contributors: Thomas Heatherwick, Heatherwick Studios, London Professor Zakaria Djeberra, University of Aalborg Professor Lars Fich, University of Aalborg Professor Edward Vessel, City College of New York Presenter: Caroline Steel Producer: Richard Walker Editor: Cathy Edwards Production Coordinator: Ishmael Soriano Studio Manager: Duncan Hannant (Image: Rear view of woman surrounded by old traditional residential buildings and lost in city, Hong Kong, China. Credit: d3sign via Getty Images)

How do you think about the internet? What does the word conjure up? Maybe a cloud? Or the flashing router in the corner of your front room? Or this magic power that connects over 5 billion people on all the continents of this planet? We might not think of it at all, beyond whether we can connect our phones to it. Another chance to hear one of our favourite episodes, inspired by a question from CrowdScience listener Simon: how much does the internet weigh? First of all, this means deciding what counts as the internet. If it is purely the electrons that form those TikTok videos and cat memes, then you might be surprised to hear that you could easily lift the internet with your little finger. But presenters Caroline Steel and Marnie Chesterton argue that there might be more, which sends them on a journey. They meet Andrew Blum, the author of the book Tubes – Behind the Scenes at the Internet, about his journey to trace the physical internet. And enlist vital help from cable-loving analyst Lane Burdette at TeleGeography, who maps the internet. To find those cables under the oceans, they travel to Porthcurno, once an uninhabited valley in rural Cornwall, now home to the Museum of Global Communications thanks to its status as a hub in the modern map of worldwide communications. With the museum’s Susan Heritage-Tilley, they compare original telegraph cables and modern fibre optics. The team also head to a remote Canadian post office, so correspondent Meral Jamal can intercept folk picking up their satellite internet receivers, and ask to weigh them. A seemingly innocuous question becomes the quest for everything that connects us... and its weight! Producer: Marnie Chesterton Presenters: Marnie Chesterton & Caroline Steel Editors: Richard Collings & Cathy Edwards Production Coordinators: Jonathan Harris & Ishmael Soriano Studio Manager: Donald MacDonald (Image: Blue scales with computer coding terms. Credit: Alengo via Getty Images)

Snakes are often seen as slithery, slimy and scary. But these intriguing non-legged creatures have made CrowdScience listener Okello from Uganda wonder how they move – more specifically, he wants to know how they climb trees so easily, and so fast. Presenter Caroline Steel meets snake expert Mark O’Shea to investigate the ingenious methods different snakes use to scale a tree trunk, and gets a demonstration from a very agreeable corn snake at a zoo. Snake movement isn’t just your typical S-shaped slithering: these reptiles move in a remarkably diverse range of ways. Melissa Miller from the University of Florida explains all the range of motion snakes can employ to effectively travel along the ground as well as at height. Caroline witnesses this in action as we pay a steamy visit to the Everglades National Park in Florida, USA, tracking pythons across the vast swamps there. We find out why understanding these pythons’ movement is vitally important for conserving the local ecosystem. Contributors: Dr Melissa Miller, Research Assistant Scientist, University of Florida Brandon Welty, Wildlife Biologist, University of Florida Prof Mark O’Shea MBE, Professor of Herpetology, University of Wolverhampton Presenter: Caroline Steel Producer: Hannah Fisher Editor: Cathy Edwards Production Co-ordinator: Ishmael Soriano Studio Manager: Neva Missirian

The CrowdScience team like a challenge. And listeners Jenny and Kai in the UK have come to us with a big one. They want to know how many flies have ever existed. Flies first appeared around 270 million years ago, so presenter Caroline Steel prepares herself to calculate a very, very large number indeed. She enlists the help of Dr Erica McAlister, Curator of Flies at the Natural History Museum in London. As Erica introduces her to specimens from the Museum’s collection of over 30 million insects, they start with the basics. Like... how do you define a fly in the first place? Caroline also explores the incredible diversity of flies… from fast-moving predators like robber flies which catch other insects on the wing to midges which are a vital part of chocolate-production; and from blood-sucking mosquitoes which transmit fatal diseases to the housefly buzzing lazily around a room. And that leads to another fly-related question. Listener Brendan in Colombia wonders why they always fly in circles around a particular area of his apartment. For an explanation we turn to Prof. Jochen Zeil from the Australian National University who reveals that this apparently aimless behaviour is, in fact, a battle for sex. And Collin in Barbados has e-mailed to ask how flies and mosquitoes benefit us. He’s had first-hand experience of their negative effects through contracting the disease chikungunya from a mosquito bite so he’s wondering if these insects are anything other than a nuisance. However, passionate fly advocate Erica McAlister is ready with plenty of reasons that we should be extremely grateful for them! Contributors: Dr Erica McAlister, Natural History Museum, London Dr David Yeates, Director, Australian National Insect Collection Prof. Jochen Zeil, Australian National University Prof. Jo Lines, London School of Hygiene and Tropical Medicine Presenter: Caroline Steel Producer: Jeremy Grange Editor: Cathy Edwards Production Co-ordinator: Ishmael Soriano Studio Manager: Sarah Hockley (Image: Close-up of insect on leaf, Kageshwori Manohara, Bagmati Province, Nepal. Credit: Aashish Shrestha via Getty Images)

It’s hard to imagine something as mind-bogglingly small as an atom. But CrowdScience listener Alan has been attempting to do just that. All things in nature appear to be different and unique; like trees and snowflakes, could it be that no two atoms are ever the same? Alan isn’t the first person to wonder this. Philosopher and scientist Gottfried Leibnitz had a similar idea in the 17th century; in this episode, philosopher of physics Eleanor Knox helps us unpick the very idea of uniqueness. And with the help of physicist Andrew Pontzen, presenter Anand Jagatia zooms into the nucleus of an atom in search of answers. Listener Alan has a hunch that the constant movement of electrons means no atom is exactly the same at any given moment in time. Is that hunch right? We discover that the world of tiny subatomic particles is even stranger than it might seem once you get into quantum realms. Can we pinpoint where uniqueness begins? And if the universe is infinite, is uniqueness even possible? In the podcast edition of this show, we peer into that expansive universe, as we discover that the quantum world of hydrogen - the tiniest and most abundant of all atoms - allows us to observe galaxies far, far away. Featuring: Dr Eleanor Knox – King’s College London Prof Andrew Pontzen – University College London Dr Sarah Blyth – University of Cape Town Dr Lucia Marchetti – University of Cape Town Presented by Anand Jagatia Produced by Florian Bohr Editor: Cathy Edwards Production Coordinators: Ishmael Soriano and Liz Tuohy Studio Manager: Emma Harth (Photo: Twelve snow crystals photographed under a microscope, circa 1935. Credit: Herbert/Archive Photos/Getty Images)

Listener Julie lives close to the coast in New Zealand and wants to know why the water that washes up on the beach isn't fresh. How exactly does all that salt get into the world's oceans? In India, a country where salt became symbolic of much more than well-seasoned food, host Chhavi Sachdev visits coastal salt farms and a research institute dedicated to studying all things saline, to better understand our relationship with salty seas. The team also ventures to a very briny lake on the other side of the globe in Salt Lake City, Utah, to learn how salt makes its way into water bodies. Speaking to an expert in deep sea exploration, we learn how hydrothermal vents may play a role in regulating ocean saltiness, and how much the field still has to explore. Meanwhile, listener Will wants to know how much melting ice sheets are affecting ocean salinity. But ice melt isn’t the only thing affecting salt levels when it comes to the impacts of climate change. And... how many teaspoons of salt are in a kilogram of sea water anyway? We do the rigorous science to answer all these salient saline questions. Featuring: Deepika - small scale salt farmer Mark Radwin - PhD candidate in geology and geophysics at the University of Utah Brenda Bowen - Geology & Geophysics, Atmospheric Sciences, University of Utah Chris German - Geology & Geophysics, Woods Hole Oceanographic Institution Prasan Khemka - Chandan Salt Works Paul Durack - Lawrence Livermore National Laboratory Bhoomi Andharia - Central Salt & Marine Chemicals Research Institute Presenter: Chhavi Sachdev Producer: Sam Baker Editor: Cathy Edwards Production Coordinator: Liz Tuohy Studio Manager: Sarah Hockley (Photo: Shiv Salt Works, Bhavnagar, Gujarat in India. Credit: Chhavi Sachdev, BBC)

CrowdScience listener Eleanor was lying in bed one rainy evening, listening to the radio. She lives in New Zealand, but happened to hear a weather forecast that told her it was raining in the UK too. She started wondering: could it be the same rain falling there and outside her window in New Zealand? Can a raindrop really travel all the way around the world? There are a number of routes the droplet could take, including traveling as moisture in the air. Presenter Caroline Steel meets meteorologist Kei Yoshimura, who puts his powerful weather simulation to work plotting the raindrop’s journey through the sky. What if the raindrop falls along the way and gets trapped? Where might it end up? Hydrologist Marc Bierkens talks Caroline through the detours it could take, ranging from short stop-offs in plant stems to extremely long delays in deep groundwater. Finally, could the drop of water make it to New Zealand by circulating through the world’s ocean currents? Oceanographer Kathy Gunn maps the droplet’s path through the ocean – and explains how climate change might affect its journey. Featuring: Prof. Kei Yoshimura, Professor of Isotope Meteorology, University of Tokyo Prof. Marc Bierkens, Professor of Earth Surface Hydrology at Utrecht University Dr. Kathy Gunn, Lecturer in Climate Sciences at the University of Southampton Presenter: Caroline Steel Producer: Phil Sansom Editor: Cathy Edwards Production Co-ordinator: Liz Tuohy Studio Manager: Tim Heffer Additional recording: Knut Heinatz (Photo: Textures of rain on the surface of the ocean. Credit: Philip Thurston/Getty Images)

It’s often said that fine wine gets better with time, and this week’s oenophile listener Jeremy has a cellar full of dust-covered bottles. He is curious whether chemistry can account for the range of flavours that develop as wine matures, but also wonders why some of it tastes like vinegar if you leave it too long? We head off to the Bordeaux region of France, where vines were planted almost 2,000 years ago. Here, winemakers are joining forces with scientists to better understand wine ageing, a process so subtle and intricate that even the scientists refer to it as magic. In the world-famous vineyards of Chateau Margaux, presenter Marnie Chesterton learns that the key ingredient for good grapes is a sandy soil type; and that in this part of France, the warming climate is actually having a positive effect on the vines, which need very little water to thrive. Over in the lab, we meet the chemist mapping the molecules responsible for aromas associated with a well-aged Bordeaux. Featuring: Philippe Bascaules, Chateau Margaux Prof Cornelis van Leeuwen, Bordeaux Sciences Agro Dr Stephanie Marchand-Marion, ISVV Alexandre Pons, ISVV Presented by Marnie Chesterton Producer – Marijke Peters Editor – Cathy Edwards Production Co-ordinator – Liz Tuohy Studio Manager – Sarah Hockley (Photo: Aged bottles on wine racks in a cellar. Credit: Morsa Images/Getty Images)

The Blue Ridge Parkway is 469 miles of beautiful vistas, a mountainous road that winds from Virginia to North Carolina in the USA. The route is peppered with elevation signs, telling you how many metres above sea level you are. Which has CrowdScience listener Beth wondering: as we are told that sea level is rising, will all the elevation signs need repainting? It’s a task she’s passed over to the CrowdScience team, who like a difficult challenge. The height of an enormous pile of rock like Ben Nevis, or Mount Everest feels unchangeable. But we measure them relative to the nearest patch of sea, which is where our story becomes complicated. Unlike water in a bath, sea level is not equal around the world. The east coast of America has a different sea level to its west coast. And as host Marnie Chesterton discovers in Finland, in some parts of the world the land is being pushed up, so sea level is actually falling. In fact, when nothing on earth - not the sea, the shore or the mountains - seems to be stable or constant, the question of what you measure from and to becomes incredibly tricky. But that hasn’t stopped oceanography and geography scientists risking life and fingers to use an ever-evolving array of technologies to find answers. In this show we find out why they care so much, and why we should too. Featuring: Dr Paul Bell – National Oceanography Centre, Liverpool, UK Dr Severine Fournier – NASA Jet Propulsion Laboratory / California Institute of Technology Dr Jani Särkkä – Finnish Meteorological Institute Khimlal Gautam – Mountaineer and Chief Survey Officer, Government of Nepal Dr Derek van Westrum – National Oceanic and Atmospheric Administration, USA Presented and produced by Marnie Chesterton Editor – Cathy Edwards Production Co-ordinator – Liz Tuohy Studio Manager – Steve Greenwood (Photo: Sea Level Elevation Sign in Death Valley, California. Credit: Mitch Diamond/Getty Images)

Prayer and meditation are key features of religious and spiritual practices around the world, suggesting they’re intimately linked to the human condition. But what is going on in the brain during prayer? And is praying beneficial for our mental health? CrowdScience listener Hilary is keen to find answers to such questions. She’s a counsellor with a strong Christian faith, and is curious to know whether science can illuminate religious and spiritual practices. Presenter Caroline Steel talks to neuroscientists researching how our brains respond to prayer and meditation; and practices mindfulness herself to explore its similarities to prayer. She discovers that having a relationship with God may depend on more than religious practice. And is there a ‘spiritual part’ to our brains? Or is prayer just one activity among many - like going for a walk or playing music - that can have similar effects on our state of mind? Featuring: Professor Andrew Newberg, Director of Research Marcus Institute of Integrative Health, Thomas Jefferson University and Hospital, USA Tessa Watt, mindfulness teacher Ven. Hin Hung Sik, Centre of Buddhist Studies, University of Hong Kong Dr Junling Gao, Centre of Buddhist Studies, University of Hong Kong Dr Blake Victor Kent, Westmont College, USA Presenter: Caroline Steel Producer: Jo Glanville Editor: Cathy Edwards Studio Manager: Tim Heffer Production Co-ordinator: Liz Tuohy (Photo: A crowd of people praying. Credit: Digital Vision/Getty Images)

Mosquitoes are responsible for more human deaths than any other animal. These tiny creatures transmit many diseases, but the most devastating is malaria. It kills over half a million people every year, most of them children. So why are people still dying of malaria in such large numbers, when so much time and money has been invested in trying to eradicate it? What do we know about mosquitoes and malaria, and what do we still need to learn? CrowdScience visits Malawi, one of the African countries leading the way against malaria, with the rollout of the world’s first malaria vaccine programme. Presenter Caroline Steel is joined by a live audience and a panel of experts: Wongani Nygulu, Eggrey Aisha Kambewa and Steve Gowelo. Together they explore questions from our listeners in Malawi and around the world, like why female mosquitoes feed on blood while males drink nectar; why some people are more likely to be bitten by mosquitoes than others; and how we might modify the insects’ DNA to stop them spreading diseases. About half a million children across Malawi have been vaccinated since 2019. We visit a clinic in nearby Chikwawa to meet the staff involved in the vaccination programme there, and the mothers embracing the opportunity to protect their babies against this deadly disease. Recorded at Malawi Liverpool Wellcome Trust (MLW), Blantyre, Malawi. Contributors: Dr. Wongani Nygulu, Epidemiologist, Malaria Alert Centre Eggrey Aisha Kambewa, MLW entomologist, MLW Dr. Steve Gowelo, University of California San Francisco Malaria Elimination Initiative Presenter: Caroline Steel Producer: Jeremy Grange Researcher: Imaan Moin Additional Recording: Margaret Sessa Hawkins & Sophie Ormiston Editor: Cathy Edwards Production Co-ordinator: Liz Tuohy (Photo: A mosquito, that is silhouetted against the moon, bites a human arm. Credit: LWA/Getty Images)

When CrowdScience listener Israel from Papua New Guinea received a bad grade on a maths test in third grade, he looked around the class and realised that almost all the other students had received a better result. Since then, he has always wondered: why are some people better at maths than others? And Israel isn’t the only one to think about this: our listeners from all over the world describe their relationships with numbers, which run the full gamut from love to hate. So are we all in control of our own mathematical fate, or are some people just naturally bad at it? Presenter Anand Jagatia hears about studies of identical and non-identical twins showing how genetics and environment interact to shape our mathematical abilities. Our numerical abilities are not set in stone. It’s always possible to improve, and getting rid of negative feelings and anxiety around maths could be the key, says psychologist Iro Xenidou-Dervou. Some countries seem to support children’s maths skills better than others. China and Finland both rank highly in international league tables; education experts in both countries discuss whether there are any keys to a successful mathematics education. And there is something underlying our ability to do maths in the first place: our number sense. We hear what happens when this number sense does not work as intended – and what can be done about it. Contributors: Professor Yulia Kovas – Goldsmiths University of London, UK Professor Pekka Räsänen – University of Turku, Finland Assistant Professor Zhenzhen Miao – Jiangxi Normal University, China Dr Iro Xenidou-Dervou – Loughborough University, UK Professor Brian Butterworth – University College London, UK Presented by Anand Jagatia Produced by Florian Bohr Editor: Cathy Edwards Production Co-ordinator: Liz Tuohy Studio Manager: Jackie Margerum (Photo: Boy scratching head in front of blackboard. Credit: Jose Luis Pelaez Inc/Getty Images)

Coastlines around the world are changing, causing serious problems for the many communities living near the sea, as well as vital and fragile coastal ecosystems. In the second of a two-part special on coastal erosion, CrowdScience explores the best ways to tackle this problem. Presenter Caroline Steel visits the Caribbean island of Puerto Rico to see the various methods they use to protect their coasts. First up: ‘riprap’ – rocks strategically placed to keep the encroaching sea at bay. The problem is, while it protects the area immediately behind the rocks, riprap can exacerbate erosion nearby. But there are other, more nature-friendly solutions, including sand dune restoration. Caroline picks up her shovel and helps to re-plant dunes, destroyed in the past by erosion as well as sand extraction for the construction trade. The roots of these plants stabilise the dunes, while building boardwalks prevents further damage from humans. Nature also offers the perfect offshore protection against coastal erosion: coral reefs. These are the first line of defence in absorbing the power of the ocean’s waves. Down on the beach, we see for ourselves just how effective they are. The reefs face threats, but restoration plans are afoot. We visit a nursery that grows corals to plant out on the reefs – and find out about corals’ surprising cannibalistic tendencies in the process. Featuring: Professor Robert Mayer - Director of Vida Marina, Center for Conservation and Ecological Restoration, University of Puerto Rico Nada Nigaglioni - Biology student, University of Puerto Rico Ernesto Diaz - Caribbean Regional Manager at TetraTech Dr Stacey Williams - Executive Director, ISER Caribe Presenter: Caroline Steel Producer: Hannah Fisher Editor: Cathy Edwards Production Co-ordinator: Liz Tuohy Studio Manager: Emma Harth (Photo: Coast restoration measures at Ultimo Trolley Beach, Puerto Rico. Credit: BBC)

Around the world, coastlines are constantly changing due to the power of waves, currents and tides. Coastal areas are also some of the most heavily populated and developed land areas in the world. So it’s not hard to see how the natural process of coastal erosion can cause serious problems for us. It’s an issue that’s been bothering CrowdScience listener Anne in Miami Beach, Florida. She can see the beach from her window and wonders why after every storm, several trucks arrive to dump more sand on it. In this first of two programmes, CrowdScience visits Anne’s home in south Florida and finds out how erosion threatens Florida’s famous beaches. Caroline Steel speaks to geoscientist Dr Tiffany Roberts Briggs and hears why it’s such a problem for this tourist-reliant state. Tiffany explains the delicate balance between natural processes and human infrastructure. Meanwhile, the Caribbean island of Puerto Rico declared a state of emergency in April 2023 due to coastal erosion. Caroline witnesses the impacts of erosion first-hand, as Ruperto Chaparro shows her abandoned houses crumbling into the sea. But how can we quantify the rate of erosion? Dr Kevian Perez in the Graduate School of Planning at University of Puerto Rico explains the methods they use to monitor Puerto Rico’s coastlines, and how they are evaluating the effectiveness of different mitigation methods. However, some of the methods used to protect coastal communities from the encroaching sea have done more harm than good. So what are the best ways to tackle this problem? That’s what we’ll be exploring in next week’s programme. Presenter: Caroline Steel Producer: Hannah Fisher Editor: Cathy Edwards Production Co-ordinator: Liz Tuohy Studio Manager: Steve Greenwood and Bob Nettles Featuring: Dr Tiffany Roberts Briggs, Associate Professor at Florida Atlantic University Ruperto Chaparro, Director of Sea Grant Programme, University of Puerto Rico Anabela Fuentes Garcia, Villa Cristiana community leader Dr Kevian Perez, researcher at the Coastal Research and Planning Institute of Puerto Rico at the Graduate School of Planning (Photo: Puerto Rico after Hurricane Maria. Credit: Orlando Sentinel/Getty Images)

How do we know where a sound is coming from? Another chance to hear this ear-opening episode, exploring a question from CrowdScience listener Chiletso. One day, he heard his son bounce a ball and instantly knew the direction it was travelling. How? Anand Jagatia sets out to discover what makes left, right, up and down sound so different. First, he gets blindfolded, so Alan Archer-Boyd, former auditory scientist and lead engineer at BBC R&D, can put his sound localisation skills to the test. It turns out that having two ears and pinnae, those flappy bits of cartilage on the side of your head, help a lot. Professor Eric Knudsen shares how the barn owl’s asymmetrical ears allow it to hunt mice, even in complete darkness. And Anand uncovers how far he can push his own spatial hearing. Blind activist and researcher Thomas Tajo teaches him how to echolocate like a bat, and Dr Lore Thaler explains what is going on in the brain of experienced echolocators. This programme was originally broadcast in March 2023. Presented by Anand Jagatia Produced by Florian Bohr for the BBC World Service Image: Boy with hands at his ears Credit: Silke Woweries/Getty Images

Today there are over eight billion people on Earth. That’s an awe-inspiring figure… but how does it compare to the vast numbers who came before us? Listener Alpha wants to know how many people have ever existed, so CrowdScience sets out to do a historical headcount. The Population Reference Bureau in the USA estimated this number back in the 90s, and have been updating their calculations ever since. Demographer Toshiko Kaneda explains how their model works, the assumptions it makes – and the huge uncertainties around the number it comes out with. We first need a date for when ‘humans’ first began, so Caroline travels to the Natural History Museum in London to meet human evolution expert Chris Stringer, and marvel at his collection of replica fossil skulls. Chris demonstrates how to distinguish our species, Homo sapiens, from other species like Neanderthals. When did these species first appear - and which of them count as human? And once you know where to start the clock, how do you estimate the numbers of people alive at different points in history? For a population demographer like Walter Scheidel, it helps that some ancient civilisations kept detailed censuses, a few of which have survived to the present day. Caroline and Walter pour over one of these census fragments, and learn how to combine them with other archaeological clues to get some very rough numbers. And finally: what does the future of our population look like? Poonam Muttreja from the Population Foundation of India discusses developments in the world’s most populous country, as well as the big demographic trends ahead for humanity. Presenter: Caroline Steel Producer: Phil Sansom Additional Recording: Umaru Fofana Editor: Cathy Edwards Production Co-ordinator: Connor Morgans Studio Manager: Sue Maillot Featuring: Toshiko Kaneda, Technical Director of Demographic Research, Population Reference Bureau Chris Stringer, Research Leader in Human Evolution, Natural History Museum London Walter Scheidel, Professor of Classics and History, Stanford University Poonam Muttreja, Executive Director, Population Foundation of India

We spend a lot of our time thinking about climate change, but listener Paul has a question that isn’t usually part of the conversation. He wants to know whether a hotter atmosphere will affect how often volcanoes erupt, or make them more explosive when they do. CrowdScience travels to New Zealand to search for answers, exploring volcanic craters and discovering traditional Maori knowledge about volcanoes. Contributors: Geoff Kilgour, Volcanologist, Geological and Nuclear Sciences Taupo, New Zealand Heather Handley, Volcanologist, University of Twente, The Netherlands Pouroto Ngaropo, Historian and Matauranga Māori expert, Rotorua, New Zealand Presenter: Caroline Steel Producer: Emily Bird Editor: Cathy Edwards Production Co-Ordinator: Connor Morgans Sound Engineer: Steve Greenwood (Photo: Icelandic volcano. Credit: KRISTINN MAGNUSSON/Getty Images)

Many of us have habits that calm us down in times of stress. Things we find deeply comforting, like sucking our thumb or biting our nails. We might not even be aware we’re doing them, but they play a fundamental role in helping us regulate our emotions. Our question this week comes from CrowdScience listener and nail-biter, Ash. He wants to know where these habits come from. And since his pet dog is also a nail-biter: do we share these traits with other animals? Recently, a video of a mouse cleaning up a man’s shed took the internet by storm. Was this a house-proud mouse, or was it the animal's way of making sense of a frenetic environment? An emerging field of scientists focusing on animal behaviour and emotions help us shed some light on such questions. Along the way we meet a dog training specialist, learn what a sniffari is, go for playtime with a thumb-sucking otter, and visit an OCD clinic. We’ll also be getting tips on how to give your pets the best home environment, and meet an animal enrichment officer in South Africa, who knows how to spot the signs of an unhelpful habit developing. Contributors: Karolina Westlund, Ethologist, Stockholm University and ILLIS Ben Terry, CBT Therapist, Priory Hospital North London Karin Pienaar, Animal Behaviourist, COAPE International Candice Ward, Animal Behaviourist, Johannesburg Zoo Jaak Panksepp clip: The science of emotions: Jaak Panksepp at TEDxRainier Producer: Robbie Wojciechowski Presenter: Alex Lathbridge Editor: Cathy Edwards Production co-ordinator: Connor Morgans Additional recording by Elna Schutz (Photo: Portrait of border collie puppy biting a curtain. Credit: Rawlstock/Getty Images)

Crowd Science listener Maik wants to know what the BMI is and what his BMI score says about his body. He trains dogs for a living and wonders if, like different breeds of dog, we simply have different body types? Marnie Chesterton comes up with some answers, talking to doctors about how the BMI is used and misused in clinical practice, and looks at some alternative methods for measuring our body composition. She also sits down with philosopher Kate Manne to discuss the realities of living in a fat-phobic world. We hear from Tonga in the South Pacific, where high BMI scores have labelled the country highly obese. But this is not necessarily how Tongans see themselves. And Marnie finds out if the BMI will continue to be used across the world as an important health marker or whether it is destined for the scrap heap of medical history. Contributors: Professor Kate Manne Dr Francesco Rubino Dr Naveed Sattar Professor Brendon Noble Technician Leah Siegel Fononga Pulu Sela Latailakepa Presenter: Marnie Chesterton Producer: Richard Walker Editor: Cathy Edwards Production co-ordinator: Connor Morgans Studio manager: Emma Harth