The world is affected by an obesity epidemic, but why is it that not everyone is succumbing? Medical science has been obsessed with this subject and is coming up with some unexpected answers. As it turns out, it is not all about exercise and diet. At the centre of this programme is a controversial overeating experiment that aims to identify exactly what it is about some people that makes it hard for them to bulk up.

We are in the grip of an allergy epidemic. 50 years ago one in 30 were affected, but in Britain today it is closer to one in three. Why this should be is one of modern medicine's greatest puzzles. In search of answers, Horizon travels round the globe, from the remotest inhabited island to the polluted centres of California and the UK. We meet sufferers and the scientists who have dedicated their lives trying to answer the mystery of why we are becoming allergic to our world.

It's 3.5 million years ago and in East Africa a remarkable species of ape roams the land. Australopithecus afarensis has taken the first tentative steps towards humanity by standing and walking on two legs. The rift valley was forming, and the rain forests dying as Africa dried out - turning the landscape into a mosaic of scattered trees and grass. In this new environment afarensis found it more efficient to move about on two legs rather than four.

This programme focuses on the most famous Roman of all - Caesar. Charming, savage, power-crazed, opportunistic and brilliant, he overthrew a 500-year-old Republic and began the age of the emperors.

The documentary chronicles the fall of the Atari Corporation through the lens of one of the biggest mysteries of all time, dubbed 'The Great Video Game Burial of 1983'. As the story goes, the Atari Corporation, faced with an overwhelmingly negative response to 'E.T.', the video game for the Atari 2600, disposed of hundreds of thousands of unsold game cartridges by burying them in the small town of Alamogordo, New Mexico.

The coast is the dynamic border between land and sea; powered by the tides and thrashed by waves, this is a world of continuous change. Opportunities never last long here, so hunters are always in a race against time. The coast is the only place on the planet where predators from air, land and sea come together. Dolphins that leave the safety of the sea to fish, walking octopuses, ingenious monkeys, fishing wolves and the greatest gathering of feeding humpback whales come to the coast to hunt. For all, timing is everything.