Sex is the key to the immortality of genes, and any tactic necessary will be deployed in the cause of reproduction - even if it's suicidal to the participant. This episode explores many of the most ingenious, complex, and dramatic methods that animals employ to ensure the continuation of their genetic line.

Having explained the science behind global warming, and addressed the arguments of the climate change sceptics earlier in the series, Dr Iain Stewart concludes the series by looking at the biggest challenge now facing climate scientists - Just how can they predict exactly what changes global warming will bring?
It's a journey that takes him from early attempts to model the climate system with dishpans, to supercomputers, and to the frontline of climate research today: Greenland. Most worryingly he discovers that scientists are becoming increasingly concerned that their models are actually underestimating the speed of changes already underway.

The Russian Arctic is one of the world’s most extreme habitats, yet it is a haven for polar bears, lemmings, arctic foxes and walruses. In late August, massive muskoxen bulls gather together to compete for mating dominance. Each bull can weigh 400 kilogram’s and charge at a speed of 40 kilometres an hour; a head-to-head impact can be heard more than a kilometre away

It's not all about the pouches. These mammalian misfits are full of surprises, from flamboyant kangaroo showdowns to rattling koala mating calls. They might seem a bit bizarre but don't underestimate them. With unexpected superpowers and amazing adaptability, they have conquered a continent.

One extraordinary family of fish has achieved the ultimate form of gender equality. When it comes to breeding, seahorses do it like no other animal on the planet. Their fierce females refuse to be left holding the baby. So it's the males that carry their brood. In this episode we explore the world of mating seahorses which are the only animals in the world that have a major gender role reversal.

In an enthralling documentary, Dan Snow and archaeologist Raksha Dave delve into the catastrophic impact of the Black Death on Britain 700 years ago, a pandemic that extinguished around half of the population, or three million people. The duo embarks on a journey to trace the origins and merciless spread of the plague, starting from its arrival on Britain's South coast in June 1348, through the bustling trade routes that brought the disease to Melcombe Regis, Dorset. Their investigation takes them to various hotspots of the outbreak, including the Old Operating Theatre in London and Wildwood Animal Sanctuary in Kent, where they explore the role of rats in dispersing the bubonic plague. Through dramatic reconstructions and visits to places like Nottingham University's biomedical laboratories, they uncover the rapid spread and deadly impact of the plague, offering a month-by-month account of how it ravaged the country, decimating cities, towns, and villages alike.
The documentary not only showcases the horrific symptoms and desperate attempts at cures through brutal medical practices of the time but also leverages cutting-edge research to explain why the Black Death remains the deadliest pandemic in history. The personal stories of victims, from princes to paupers, are brought to light, revealing the indiscriminate nature of the disease. Dan's visit to Canterbury Cathedral and Raksha's investigation into the recent discovery of mass graves beneath a tranquil London square underline the widespread desperation and devastation. Their journey through the history of the Black Death, culminating in the discovery of its indiscriminate toll and the unveiling of mass graves in London, not only sheds light on the darkest chapters of British history but also ignites a profound understanding of the tragedy, making a compelling case for why this documentary is a must-watch for anyone interested in the profound impacts of pandemics on human society.