When ancient Greece fell into decline, mathematical progress stagnated as Europe entered the Dark Ages, but in the East mathematics reached new heights. In the second episode, Du Sautoy explores how maths helped build imperial China and discovers how the symbol for the number zero was invented in India. He also looks at the Middle Eastern invention of algebra and how mathematicians such as Fibonacci spread Eastern knowledge to the West.

The terrorist group Boko Haram is responsible for thousands of deaths in Nigeria. Now, the government is determined to drive these militants from the country. But is the hunt for insurgents causing as much harm as it's preventing? Former Navy SEAL and new VICE correspondent Kaj Larsen travels to Nigeria to see what this cat-and-mouse game means for the people caught in the middle of the fight. 'Unnatural Selection': For centuries, scientists have been working to change the genetic traits of plants and animals. Now, the new gene-editing method CRISPR has made that process astonishingly simple - so simple it could easily be used on humans. Isobel Yeung reports from Brazil, Scotland, China and the U.S. on the technological advances that could reshape evolution as we know it.

Mountain biking requires endurance, core strength and balance, bike handling skills, and self-reliance. Advanced riders pursue both steep technical descents and high incline climbs. In the case of freeriding, down hilling, and dirt jumping, aerial manoeuvres are performed off both natural features and specially constructed jumps and ramps. Follows several individuals breaking out of their mundane lives and entering into the adventurous thrill-seeking world of this sport.

Ever wonder what's happening inside your head? From dreaming to anxiety disorders, discover how your brain works with this illuminating series. The first episode looks at how memory works and examines the way in which the brain stores, processes, and retrains memories. It also looks at the ways in which memory can fail and discusses how memories can warp over time. It talks to neuroscientists and a memory champion who explains her techniques.

The Red Sea is one of the youngest oceans in the world and one of the warmest. The northern region, with its diverse array of marine life, is one of the most visited dive locations on earth while the southern end remains virtually unexplored. It's a global hotspot for marine biology and an important trade route throughout human history, linking the trade goods of India and the Far East with the markets of Egypt and Europe.

Dr Alice Roberts looks at our ancestors' seemingly impossible journey to Australia. Miraculously preserved footprints and very old human fossils buried in the outback suggest a mystery: that humans reached Australia almost before anywhere else. How could they have travelled so far from Africa, crossing the open sea on the way, and do it thousands of years before they made it to Europe? The evidence trail is faint and difficult to pick up, but Alice takes on the challenge. In India, new discoveries among the debris of a super volcano hint that our species started the journey much earlier than previously thought, while in Malaysia, genetics points to an ancient trail still detectable in the DNA of tribes today. Alice travels deep into the Asian rainforests in search of the first cavemen of Borneo and tests out a Stone Age raft to see whether sea travel would have been possible thousands of years ago, before coming to a powerful conclusion.