Becky Ripley and Emily Knight dig deep into the underground web of plant roots and mycorrhizal fungi networks. Here lies a 400 million year old market economy, founded on the trading of resources. Nutrients are traded for carbon. Carbon is traded for nutrients. And the exchange rate between the two is constantly in flux, to level supply with demand.

This highly-evolved symbiosis between plant and fungi is crucial to the survival of over 80% of all terrestrial plants. And it also acts as a colossal carbon store. A recent study found that 13 billion tons of CO2 are passed from plants to mycorrhizal fungi each year. It's one of the most effective and important market trading relationships in the world.

And it turns out, these belowground trade deals are not so different to the aboveground deals that play out within our own market trading economy. Both move and shake to the very same economic principles of supply and demand. Can our economic theories be applied back to the fungi-plant deals in order for the fungi to capture more carbon in the face of climate change? Or, flip-reverse it, can we apply some of their age-old trading strategies to our own economic models? They may not have a brain, but they have 400 million years of evolution under their belt, so their trade strategies may well be more streamlined and more symbiotic compared to ours.

Featuring Dr Bethan Manley, fungal geneticist and data scientist at The Society for the Protection of Underground Networks, and Dr Ted Loch-Temzelides, Professor of Sustainable Development at the Department of Economics at Rice University. Produced and presented by Emily Knight and Becky Ripley.

Becky Ripley and Emily Knight explore whether we can ever know what others know, and how we figure out if they're telling fibs.

Beneath the surface of the ocean, darting around in the dappled sunlight of the reef, you can find some of nature's most prolific liars. The cephalopods. Squid, octopus and cuttlefish; filthy con artists, the lot of them. They communicate with each other, and with both predators and prey, using dazzling patterns of shifting colour and texture on the surface of their skin. The messages they send can be sophisticated, but they're not always honest; males pretending to be females, octopuses pretending to be sea-snakes, cuttlefish on the hunt for love, pretending to have more innocent intentions. To deceive another, you might think, implies a level of understanding about what that other being knows, or is thinking. The philosophers call this Theory of Mind. But how much do the cuttlefish really KNOW about the tall tales they tell - and how much can we deduce about their intelligence as a result?

If cuttlefish are some of nature's best liars, let's meet some of the worst: human toddlers. Oh they lie alright, but they're terrible at it - they tell the most outrageous fibs that we can all see through. That's because they are just beginning to develop the complex skills of Theory of Mind for themselves, and they haven't quite perfected it. How they lie, and how they learn to do it better, gives us fascinating insights into the developing mind of a child.

Featuring Dr Jon Copley, professor of Ocean Exploration at the University of Southampton, and Dr Emily Jones, from Toddlerlab, at the Centre for Brain & Cognitive Development at Birkbeck College. Produced and presented by Emily Knight and Becky Ripley.

Becky Ripley and Emily Knight tackle a topic we love to fight about: parenting. How should we raise our kids? How much love is too much?

Good parenting begins at home. And 'home', in this case, is a decomposing mouse corpse, rolled into a ball and buried 5 inches beneath the soil of the forest floor. Naturally. This is the home of one of nature's most diligent little parents, the black and orange Gravedigger, or Burying Beetle. The two parents team up to feed, nurture and care for their grubs until they're old enough to make it alone. But is there such a thing as too much parenting? Could a little LESS motherly (and fatherly) love, actually help the grubs be a little more self-reliant?

In the human world, we can't seem to agree on the best way to raise our babies. Across time and across cultures, there have been parenting strategies that seem bonkers to us now, while our ways of doing things might raise alarm bells elsewhere. One factor here is that humans spend a lot of time parenting; we're one of the most heavily investing parents the natural world has ever produced. But our babies are needy for a reason: it takes an awfully long time to make a human.

Featuring Rebecca Kilner, Professor of evolutionary biology at the University of Cambridge, and Dr Brenna Hassett, biological anthropologist at University College London and the author of 'Growing up Human: The Evolution of Childhood'. Produced and presented by Emily Knight and Becky Ripley.

Becky Ripley and Emily Knight explore the ancient origins of medicine. What makes us sick? What makes us well again? And do animals medicate like we do?

Deep in the rainforest of Sumatra, one clever orangutan called Rakus has pretty much got it figured out. Astonished researchers spotted him making and then applying a plant-based medicinal paste to a painful wound. It was anti-bacterial, anti-fungal, and it numbed his pain, helping him to heal in record time. This might be one of the more sophisticated examples out there, but Rakus is far from the only one; lots of animals are incredibly skilled at using the plants and minerals around them to heal wounds, treat infection, or stave off nasty bugs. It's called, wait for it... zoopharmacognosy.

In the human world, we've honed our own medicinal skills into something slick, sterile and very high-tech, but so many of the medicines we use today have natural origins. The age-old skills of the shamans and herbalists of the past are still extremely relevant, and we have yet to fully unlock all the healing secrets of the plants around us.

Featuring Dr Isabelle Laumer, cognitive biologist and primatologist at the Max Planck Institute for Animal Behaviour, and Sarah Edwards, Plant Records Officer from Oxford Botanic Gardens and an ethnobotanist from the University of Oxford. Produced and presented by Emily Knight and Becky Ripley.

Becky Ripley and Emily Knight dive into the watery world of rainbowfish to confront the age-old myth that fish have bad memories. In actual fact, they are much more intelligent than we like to think, with an incredible capacity for learning and memory, as seen in almost all fish species. Their ability to remember complex things over a long period of time means they can build social relationships, navigate huge distances, and even form cultures, as knowledge is passed down over generations.

So, the science has spoken: fish have way better memories than we like to think. But what about us humans? Well, turns out our memories are way worse than we like to think. From the very first perceptual moment when you experience something, your brain is constantly filtering your memories so that it only keeps the information that it thinks you need. And the more you recount a memory, the more it deviates from "the truth". Which means, in reality, we forget most of our lives, and we misremember most of the rest! Begging the question: are we who we think we are?

Featuring Professor Culum Brown, head of The Fish Lab at Macquarie University, and Dr Julia Shaw, criminal psychologist at UCL and author of 'The Memory Illusion'. Produced and presented by Emily Knight and Becky Ripley.

Becky Ripley and Emily Knight return in the series that turns to the natural world to try and make sense of what it means to be human. The new series is available from 29 July

Becky Ripley and Emily Knight tackle a serious question. One of supreme scientific importance: do animals get wasted?

From drunk moose stuck in trees, to wasted wallabies asleep in opium fields, to dippy dolphins puffing on toxic pufferfish; stories abound about animals who seem to be using their free time to get sloshed. But do these stories, delightful as they are, stand up to scrutiny? In the natural world, when your survival relies on keeping your wits about you, what could be the evolutionary purpose of dulling your wits with psychoactive drugs?

Come to think of it, why do we do it? And what's the connection between getting high, seeing God, and learning to love your neighbour?

Produced by Becky Ripley and Emily Knight. Featuring zoologist Lucy Cooke, and Professor Richard Miller at Northwestern University.

Becky Ripley and Emily Knight find out what it takes to learn the language of your people, with the help of some extremely chatty little birds.

The song of the zebra finch has been compared to a 90's dial-up modem running triple-speed, or an alien fax machine. But to a female zebra finch, it's a song of irresistible seduction. The males learn their song in a very similar way to the way we learn language, and it all starts with the babies. Through babbling, then copying, then innovating motifs of their own, the zebra finches take their language and then put their own distinctive stamp on it.

But if they don't learn it at just the right time, as a chick, they can't learn it as an adult.

How does human language acquisition work, and what would happen if you denied a baby the opportunity to learn to speak? The surprising answer takes us to 1970s Nicaragua, and the extraordinary story of the birth of a language...

Produced by Becky Ripley and Emily Knight. Featuring Professor Ofer Tchernichovski from Hunter College at CUNY, and Dr Judy Shepard-Kegl from the University of Southern Maine.

Becky Ripley and Emily Knight investigate physical fitness in the animal kingdom, and ask why animals never seem to have to go to the gym.

Consider the Barnacle Goose, getting ready for one of the most phenomenal physical challenges of the animal world: the annual migration. They leave their sedentary summer life, floating about eating reeds, and take off to fly 2,700 miles. And what do they do to prepare for this incredible feat? Absolutely nothing. They just sit around, eating as much as they can.

The physical fitness of so many animals is hard-wired into their biology. But not ours. If we want to gain muscle, we don't just wait for the seasons to change, we have to work for it. No pain no gain! And if we slack off and laze about, our muscles melt away. Why are we so different? And do I really have to go to the gym?

Produced by Becky Ripley and Emily Knight. Featuring Professor Lewis Halsey from the University of Roehampton, and Professor Dan Lieberman at Harvard University.

Becky Ripley and Emily Knight dive into the underwater world of killer whales, where tight-knit family pods are led by the eldest post-reproductive matriarch, to better understand why we have a menopause.

Matriarchal killer whales usually stop being able to reproduce in their thirties or forties, but continue to live for decades longer. This phenomenon of having a long post-reproductive life is known only to exist in 5 species: killer whales, narwhals, beluga whales, short-finned pilot whales, and humans. That’s it. Females across the rest of the animal kingdom can keep reproducing into old age, many until their dying days.

So why? If the success of a species lies in its ability to breed and pass on its genes, why have we – and a few species of whale – evolved this seemingly counter-productive thing that stops us being able to do that? What's the point of it? And what does it say about our need for grandmas?

Featuring Prof. Darren Croft, Professor of Animal Behaviour at the University of Exeter, and Dr. Brenna Hassett, Biological Anthropologist at UCL and author of Growing Up Human. Produced and presented by Emily Knight and Becky Ripley.