Rivers provide the essentials of life: fresh food and water. They often provide natural highways and enable us to live in just about every environment on Earth. But rivers can also flood, freeze or disappear altogether!Cities - Surviving the Urban Jungle Human Planet joins Sam Niang, a Laotian fisherman, as he walks a high wire strung above the raging Mekong River rapids on an extraordinary commute to work. There's also a look at the remarkable partnership between Samburu tribesmen and wild elephants in their search for water in the dried-out river beds of Northern Kenya. Plus, a father who must take his two children on a six-day trek down a frozen river - the most dangerous school run on Earth, and the ice dam busters of Ottowa with their dynamite solution to a city centre hold-up.

The turmoil of 1968 helps Nixon win the presidency. Troop strength in Vietnam peaks and the draft accelerates. Karl Marlantes endures bitter jungle fighting on Hill 484, and draftee Arthur Wiknik gets a grim introduction to combat on 'Hamburger Hill'. But shortly after winning both hills, US troops abandon them.

Dr Alice Roberts re-traces the greatest ever journey taken by our ancestors. Thousands of years ago one small group of our species, Homo sapiens, crossed out of Africa and into the unknown. Their descendants faced baking deserts, sweat-soaked jungles and frozen wildernesses and risked everything on the vast empty ocean. Within 60,000 years they colonised the whole world... How did they do it? Why do we, their descendants all look so different?

Deep in the Andean mountains lays a mysterious ruin named Machu Picchu. For 400 years it sat abandoned on its misty cliff, the quintessential lost city in the jungle. Rediscovered in 1911, it contained no written records or carvings, nothing that could shed light on its history. For a century since, it has defied the endless scores of visitors and scientists who attempted to understand its purpose. Who were the mysterious people who built it and why did they build it here? Today an international team of archaeologists, engineers and scientists are finally piecing together the clues. Together they are discovering astonishing new burials, revealing the intricacies of its ingenious engineering and finally decoding the secrets of Machu Picchu.

The Sundarbans mangrove forest, in Bangladesh near the Indian border, is a tidal jungle where Ganges and Brahmaputra enter the Indian Ocean. Its has some 400 Bengal tigers - the largest population in the world, and the only to be hardly scared of men. The downside is tigers kill up the 50 Bangladeshis a year, even from neighbouring villages, so keeping them inside the reserve is key to long-term survival.
A recent project tries to train local mongrels, not pets but fiercely self-reliant dogs, to spot and even scare off tigers from villages. An individual tiger can turn into a man-eater in order to survive - this process may occur due to an injury or old age (and so cannot hunt agile prey) or even accidentally tasting human flesh.

From steamy jungles to dry deserts, amphibians have taken their first footsteps onto land using their bizarre life histories to break their ties with the water and invade the earth.
This episode delves into the extraordinary and intimate lives of the soft skinned amphibians. This includes the marsupial frogs, a peculiar species where the father carries his young in pouches and then gives birth. It also features warring giant salamanders over a metre long and show-off newts that offer displays just like underwater birds of paradise.