Earth may seem like the most hospitable planet in the solar system. But look again. Startling new discoveries reveal the blue planet has been plagued by more chaos and destruction than scientists once imagined. Stand on the Earth billions of years ago as a primitive planet called Theia slams into it. Shiver as our entire globe is frozen over like a gigantic snowball. Feel the heat as mammoth volcanoes scorch the landscape and darken the sky. From a cosmic gamma ray burst frying away the ozone layer to an Everest-size asteroid slamming into the ocean, we'll reveal new information about how these unparalleled events drove life to the brink of total extinction. Out of this continuous devastation, how has our planet--and life--got to where it is today? Are the worst days behind us--or lurking in the distant future?

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?

One and a half million years ago, a new breed of ape-man walks the land. In southern Africa, Homo Ergaster has taken the next step to becoming human. They have long, modern looking noses, which cool air as they breathe. Their hairless bodies, with millions of tiny sweat glands, mean they don't pant anymore to control their temperature - they sweat. And, above all, they have big brains - nearly two-thirds the size of ours.

Take a dino's-eye view of life in the prehistoric past as cutting-edge filming techniques and hard science. When White Tip, a female velociraptor, loses the rest of her pack, she must struggle to survive on her own. In time, she locates a new pack, as well as a mate, only to find that her hardships are just beginning in the harsh desert environment.

From the makers of Walking With Dinosaurs comes an epic and entertaining new exploration of early life on Earth, revealing that before the age dinosaurs, a succession of fantastical animals and plants ruled the planet. A time when a two-ton predatory fish came on land to hunt, when four-metre sea scorpions sliced sushi in the shallows and when just one species of lumbering reptile represented 80 per cent of all life. For the first time, this special two-hour presentation uncovers and recreates these creatures and the bizarre world they inhabited.

'Blood Brothers' follows the lives of two species, Paranthropus boisei and Homo habilis who embody two alternative ways of ape-man life. Although heavyset, with distinctive gorilla-like faces, the boisei are gentle characters. They live within a strict social structure and are led by a dominant male whose strength and power holds the group together. The habilis have taken a different approach to survival. They don't have the specialisms of the boisei but instead have developed into the archetypal jack-of-all-trades, inquisitive scavengers prepared to try almost anything to survive. Tough, active, gregarious and noisy, they are always on the move and always alert to the possibility of a meal. But in the near drought of the dry season the habilis are struggling. It seems as if their way of life cannot help them when conditions are tough.