Becky Ripley and Emily Knight discover the hairy history of the human kiss. Where did it come from? Why do we like doing it? And how is it good for us?

Featuring Dr Adriano Lameira, primatologist turned evolutionary psychologist from the University of Warwick, and Dr Dean Burnett, neuroscientist, lecturer, and author of The Idiot Brain and The Happy Brain, among others. Produced and presented by Emily Knight and Becky Ripley.

How do we extract the maximum amount of power from the sun? Becky Ripley and Emily Knight enlist the help of a giant, thousand-year old clam. And end up in the depths of space...

Featuring Professor Alison Sweeney at Yale University, and Mike Garrett from the Jodrell Bank Centre for Astrophysics. Produced and presented by Emily Knight and Becky Ripley

Why do animals move the way they do? And why do we humans love to run? Becky Ripley and Emily Knight enlist dogs, horses, armadillos, and some uncooperative rabbits to find out.

Featuring Professor Lewis Halsey from the University of Roehampton, and Dr Andrew Yegian from Harvard University. Produced and presented by Emily Knight and Becky Ripley.

Do lower voices demand more power? Do we take them more seriously? And is this a bias that needs to be challenged more in today’s world? Becky Ripley and Emily Knight compare the bellowing roars of red deer stags to dig deeper into the psychology of human and animal voice.

Featuring David Reby, Professor of Ethology at Jean Monnet University, and David Puts, Professor of Anthropology at Pennsylvania State University. Produced and presented by Emily Knight and Becky Ripley.

Why do we help each other out? Even when it gets us nothing in return? Becky Ripley and Emily Knight explore the existence of altruism, with the help of some mischievous magpies.

Featuring Professor Dominique Potvin from the University of the Sunshine Coast, and Dr Abigail Marsh from Georgetown University.

Produced and presented by Emily Knight and Becky Ripley.

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.