Discovery

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 informationContributors: 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.

In the mid-19th Century, an Augustinian friar called Gregor Mendel made a breakthrough. By breeding pea plants and observing how certain traits were passed on, Mendel realised there must be units - little packets - of information determining characteristics. He had effectively discovered the gene.His insights inspired eugenicists from the 1900s onwards. If traits were passed on by specific genes, then their policies should stop people with ‘bad’ genes from having children.Mendel’s ideas are still used in classrooms today - to teach about traits like eye colour. But the eugenicists thought Mendel's simple explanations applied to everything - from so-called ‘feeblemindedness’ to criminality and even pauperism.Today, we recognise certain genetic conditions as being passed on in a Mendelian way. Achondroplasia - which results in short stature - is one example, caused by a single genetic variant. We hear from Professor Tom Shakespeare about the condition, about his own decision to have children despite knowing the condition was heritable - and the reaction of the medical establishment.We also explore how genetics is taught in schools today and the danger of relying on Mendel’s appealingly simple but misleading account.Contributors include Dr Brian Donovan, senior research scientist at BSCS, Prof Tom Shakespeare, disability researcher at London School of Hygiene and Tropical Medicine, and Dr Christine Patch, principal staff scientist in Genomic Counselling in the Society and Ethics Research group, part of Wellcome Connecting Science.(Photo: Johann Gregor Mendel (1822-1884). Austrian botanist, followed breeding experiments, discovered paired units of heritable characteristics. Credit: Hulton Archive/Getty Images)

In the name of eugenics, the Nazi state sterilised hundreds of thousands against their will, murdered disabled children and embarked on a programme of genocide.We like to believe that Nazi atrocities were a unique aberration, a grotesque historical outlier. But it turns out that leading American eugenicists and lawmakers like Madison Grant and Harry Laughlin inspired many of the Nazi programmes, from the mass sterilisation of those deemed ‘unfit’ to the Nuremberg laws preventing the marriage of Jews and non-Jews. Indeed, before World War Two, many eugenicists across the world regarded the Nazi regime with envious admiration.The Nazis went further, faster than anyone before them. But ultimately, the story of Nazi eugenics is one of international connection and continuity.With contributions from Prof Stefan Kühl from the University of Bielefield, Prof Amy Carney from Penn State Behrend, Dr Jonathan Spiro from Castleton University, Prof Sheila Weiss from Clarkson University and Dr Barbara Warnock from the Wiener Holocaust Library(Photo: German women carrying children of an alleged aryan purity in a Lebensborn selection centre, births by eugenicists methods during World War Two. Credit Keystone-France Getty Images)

Who should be prevented from having children? And who gets to decide? Across 20th century America, there was a battle to control birth - a battle which rages on to this day.In 1907, the state of Indiana passed the first sterilisation law in the world. Government-run institutions were granted the power to sterilise those deemed degenerate - often against their will.In the same period, women are becoming more educated, empowered and sexually liberated. In the Roaring Twenties, the flappers start dancing the Charleston and women win the right to vote.But contraception is still illegal and utterly taboo. The pioneering campaigner Margaret Sanger, begins her decades long activism to secure women access to birth control - the only way, she argues, women can be truly free.In the final part of the episode, sterilisation survivor and campaigner Elaine Riddick shares her painful but remarkable story.Contributors: Professor Alexandra Minna Stern from the UCLA Institue of Society and Genetics, Professor Wendy Kline from Purdue Univerity, Elaine and Tony Riddick from the Rebecca Project for JusticeFeaturing the voice of Joanna Monro(Photo: Elaine Riddick was sterilised without her consent, when she was 14, in North Carolina. Credit: Tami Chappell/The Washington Post/Getty Images)

"You will not replace us" was the battle cry of white supremacists at a rally in Charlottesville in 2017. They were expressing an old fear - the idea that immigrants and people of colour will out-breed and replace the dominant white 'race'. Exactly the same idea suffused American culture in the first decades of the 1900s, as millions of immigrants arrived at Ellis island from southern and eastern Europe.The 'old-stock' Americans - the white elite who ruled industry and government - latched on to replacement theory and the eugenic idea of 'race suicide'. It's all there in The Great Gatsby - F.Scott Fitzgerald's novel set in 1922 - which takes us into the world of the super-rich, their parties and their politics.Amidst this febrile period of cultural and economic transformation, the Eugenics Record Office is established. Led by Charles Davenport and Harry Laughlin, it becomes a headquarters for the scientific and political advancement of eugenics.By 1924, the eugenically informed anti-immigrant movement has triumphed - America shut its doors with the Johnson-Reed Act, and the flow of immigrants is almost completely stopped.Contributors: Dr Thomas Leonard, Professor Sarah Churchwell, Professor Joe CainPresenter: Adam Rutherford Producer: IIan Goodman(Photo: Immigrants arriving in Ellis Island, New York, 27 May 1920. Credit: Getty Images)Clips: BBC News, coverage of Charlottesville protests, 2017 / CNN, coverage of buffalo shooter, 2022 / MSNBC, coverage of buffalo shooter, 2022 / Edison, Orange, N.J, 1916, Don't bite the hand that's feeding you, Jimmie Morgan, Walter Van Brunt, Thomas Hoier / BBC Radio 4 Great Gatsby: Author, F Scott Fitzgerald Director: Gaynor Macfarlane, Dramatised by Robert Forrest.