‘Can we bring back extinct species?’ wonders listener Mikko Campbell. Well, Professor Fry is pretty excited by the prospect of woolly mammoths roaming the Siberian tundra once more. And everyone is impressed with the science that might make it happen. But Dr Rutherford comes out STRONGLY against the whole thing. Can our expert guests win him over? Dr Helen Pilcher shares the tale of Celia the lonely mountain goat, and makes the case for cloning to help protect species at risk of extinction. Professor Beth Shapiro sets out how biotech company ‘Colossal’ plans to engineer Asian elephants’ DNA to make a new group of mammoth-like creatures. And we hear how genetic technologies are being used in conservation efforts around the world. BUT WHAT ABOUT T-REXES? Not gonna happen. Sorry. Contributors: Dr Helen Pilcher, author of ‘Bring Back the King: The New Science of De-Extinction’, Professor Beth Shapiro from the University of California Santa Cruz, Dr Ben Novak of Revive and Restore and Tullis Matson from Nature’s SAFE.

The Great Pyramids of Giza are awesome feats of engineering and precision. So who built them - and how? Was it a mysteriously super-advanced civilization now oddly extinct? Was it even aliens? Nah, course not! Rutherford and Fry investigate how these inspiring monuments were really constructed, and learn about the complex civilisation and efficient bureaucracy that made them possible. Professor Sarah Parcak busts the myth that they were built by slaves. In fact, she reveals, it was gangs of well-paid blokes fuelled by the ancient Egyptian equivalent of burgers and beer. And Dr Chris Naunton explains how it was not some mysterious tech, but incredible organisation and teamwork which made it possible to transport massive stone blocks over long distances several thousand years before trucks arrived. Dr Heba Abd El Gawad points out how racism led to bizarre assumptions in the history of archaeology, and how those assumptions linger in contemporary conspiracy theories which refuse to accept that Egyptians could have built the pyramids themselves! Contributors: Professor Sarah Parcak, University of Alabama, Dr Chris Naunton, Egyptologist and broadcaster, Dr Heba Abd El Gawad, University College London

Close your eyes and think of a giraffe. Can you see it? I mean, *really* see it - in rich, vivid detail? If not - you aren’t alone! We’ve had scores of messages from listeners who report having a ‘blind mind’s eye’. They don’t see mental images at all and they want to know why. Jude from Perth wants to know what makes her brain different, and Diane from Scotland wonders whether it affectes her ability to remember family holidays. Our sleuths learn that this is a condition recently termed ‘aphantasia’. They meet the chap who came up with the name, Professor Adam Zeman, a neurologist from the University of Exeter, and quiz him on the brain mechanisms behind this mystery. Professor Julia Simner - a psychologist who, herself, doesn’t see mental images - shares the surprising research into how aphants differ slightly from others in a range of cognitive skills. We also hear about the world class artists and animators who can’t visualise - but can create beautiful, imaginary worlds. Philosophy professor Fiona Macpherson from the University of Glasgow, deepens the mystery: perhaps this largely hidden phenomenon is behind some of the most profound disagreements in the history of psychology. Our mental experiences are all very different - maybe that’s why thinkers have come up with such different theories about how our minds work. Search for the “VVIQ” or Vividness of Visual Imagery questionnaire to take the test yourself. Look for “The Perception Census” to take part in this massive online study of perceptual variation. And look up the 'Aphtantasia Network' if you're curious to find out more. Presenters: Hannah Fry and Adam Rutherford Contributors: Professor Adam Zeman, Professor Julia Simner, Professor Fiona Macpherson

We are a teeming mass of interconnected microbes and the impact of this microscopic universe on our health, our minds, even our moods, is profound. Made in collaboration with Wellcome Collection, Claudia Hammond and an expert panel explore one of the fastest moving areas of science and what it means for modern medicine. Recorded in front of a live audience at Wellcome’s Reading Room in London, Claudia discovers how our microbes could be harnessed to improve our mental and physical health. And along with the scientific insights, there are important answers to questions everybody wants to know the answer to, such as why some peoples’ “emissions” smell so badly and how having a dog or cat enriches your microbiome. On stage with Claudia are immunologist Professor Sheena Cruickshank from the University of Manchester, microbiologist Professor Glenn Gibson from the University of Reading and neuroscientist Professor John Cryan from University College Cork in Ireland. Produced by: Fiona Hill and Elisabeth Tuohy Studio Engineer: Bob Nettles and Emma Hearth Image: Scanning electron micrograph (SEM) of bacteria cultured from a sample of human faeces. Credit: Steve Gschmeissner/Science Photo Library/Getty Images

Think Sahara Desert, think intense heat and drought. We see the Sahara as an unrelenting, frazzling, white place. But geo-archaeologist Dr Judith Bunbury says in the not so distant past, the region looked more like a safari park. In the more recent New Kingdom of Ancient Egypt, from around 3500 years ago (the time of some of Egypt’s most famous kings like Ahmose I, Thutmose III, Akhenaten, Tutankhamun and queens like Hatshepsut) core samples shows evidence of rainfall, huge lakes, springs, trees, birds, hares and even gazelle, very different from today. By combining geology with archaeology, Dr Bunbury, from the department of Earth Sciences at the University of Cambridge and Senior Tutor at St Edmund’s College, tells Jim al-Khalili that evidence of how people adapted to their ever-changing landscape is buried in the mud, dust and sedimentary samples beneath these ancient sites, waiting to be discovered. The geo-archaeological research by Judith and her team, has helped to demonstrate that the building of the temples at Karnak near Luxor, added to by each of the Pharaohs, was completely dependent on the mighty Nile, a river which, over millennia, has wriggled and writhed, creating new land on one bank as it consumes land on another. Buildings and monuments were adapted and extended as the river constantly changed course.

Clifford Johnson's career to date has spanned some seemingly very different industries - from exploring quantum mechanics around string theory and black holes, to consulting on some of Hollywood's biggest movies; but it makes sense once you understand his ambition of making science accessible to all. A Professor in the Department of Physics and Astronomy at the University of Southern California in Los Angeles, Clifford's worked in the United States for decades – but was born in the UK, then spent his formative years on the Caribbean island of Montserrat, before moving back to England to study. Here, he fell in love with quantum mechanics - before moving to the US, where he's broken new ground in finding ways to talk about quantum gravity and black holes. Clifford's other big passion is getting as many people as possible engaged with science, making it more exciting, entertaining and most importantly diverse - and it's this attitude that's led to regular work as a science consultant on various TV shows and films; and even a recent cameo in a major movie.

A fur-stripped mouse carcase might not sound like the cosiest of homes – but that is where the burying beetle makes its nest, and where Rebecca Kilner has focused much of her research. A professor of evolutionary biology at the University of Cambridge, Rebecca’s work – initially with cuckoos, then more recently with beetles – has shed invaluable light on the relationship between social behaviours and evolution. She tells Jim al-Khalili how the beetles' helpfully swift generational churn and mouse-based parenting has allowed her team to study evolution in action, demonstrating for the first time what was previously just evolutionary theory.

Magnets are inside loads of everyday electronic kit - speakers, motors, phones and more - but listener Lucas is mystified. What, he wonders, is a magnetic field? Our sleuths set out to investigate the mysterious power of magnets, with the help of wizard physicist Dr Felix Flicker, lecturer in physics at Cardiff University and author of the The Magick of Matter, and materials scientist Dr Anna Ploszajski, author of Handmade. They cover the secrets of lodestones, naturally occurring magnetic rocks, how to levitate crystals, frogs and maybe even people. Matthew Swallow, the Chair of the UK Magnetics Society, explains why magnets make the best brakes for rollercoasters, and Dr Ploszajski explains how magnetically-induced eddy currents are used to sort through our recycling. Finally, Dr Flicker persuades Adam and Hannah that to really understand magnetic fields you have to leave classical physics behind, and go quantum. So our sleuths take a leap into the strange subatomic realm.

Tim Lamont is a young scientist making waves. Arriving on the Great Barrier Reef after a mass bleaching event, Tim saw his research plans disappear and was personally devastated by the destruction. But from that event he discovered a novel way to restore coral reefs. Playing the sounds of a healthy coral reef entices fish in to recolonise the wrecked reefs. Tim's emotional journey forced him to realise that environmental scientists can no longer just observe. They need to find new prisms with which to view the world and to intervene to save or protect the natural environment.

Are we entering a ‘newgenic’ age - where cutting-edge technologies and the power of personal choice could achieve the kind of genetic perfection that 20th century eugenicists were after? In 2018, a Chinese scientist illegally attempted to precision edit the genome of two embryos. It didn’t work as intended. Twin sisters - Lulu and Nana - were later born, but their identity, and the status of their health, is shrouded in secrecy. They were the first designer babies. Other technological developments are also coming together in ways that could change reproduction: IVF can produce multiple viable embryos, and polygenic screening could be used to select between them. Increased understanding and control of our genetics is seen as a threat by some - an inevitable force for division. But instead of allowing genetics to separate and rank people, perhaps there’s a way it can be used - actively - to promote equality. Professor Paige Harden shares her suggestion of an anti-eugenic politics which makes use of genetic information Contributors: Dr Helen O'Neill, lecturer in Reproductive and Molecular Genetics at University College London, Dr Jamie Metzl, author of Hacking Darwin, Professor Kathryn Paige Harden from the University of Texas and author of The Genetic Lottery: Why DNA Matters for Social Equality.