After eight grueling years of hunting in the hot, wind-scoured desert of central Africa, an international team of researchers has uncovered one of the most sensational fossil finds in living memory: the well-preserved 7 million years old skull of a chimp-size animal, probably a male, that doesn't fit any known species. According to paleontologist Michel Brunet of the University of Poitiers in France, whose team reported the find in Nature last week, there is no way it could have been an ape of any kind. It was almost certainly a hominid — a member of a subdivision of the primate family whose only living representative is modern man.

The world stood in fear of an emerging new disease that threatened to kill millions. A new flu variant H1N1 had arrived. If this latest pandemic has taught anything, it is just how little is understood about the invisible world of viruses. But that has not stopped scientists trying. Horizon follows the leading researchers from across the world, who are attempting to unravel the many secrets of viruses to understand when and why they kill.

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.

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.

For centuries scientists have been attempting to come up with an elixir of youth. Now remarkable discoveries are suggesting that ageing is something flexible that can ultimately be manipulated. The scientists are attempting to piece together why we age and more vitally for all of us, what we can do to prevent it. But which theory will prevail? Does the real key to controlling how we age lie with a five-year-old boy with an extraordinary ageing disease or with a self-experimenting Harvard professor? Could one of these breakthroughs really see our lives extend past 120 years?

Horizon uncovers the secret world of our dreams. In a series of cutting-edge experiments and personal stories, we go in search of the science behind this most enduring mystery and ask: where do dreams come from? Do they have meaning? And ultimately, why do we dream? What the film reveals is that much of what we thought we knew no longer stands true. Dreams are not simply wild imaginings but play a significant part in all our lives as they have an impact on our memories, the ability to learn, and our mental health. Most surprisingly, we find nightmares, too, are beneficial and may even explain the survival of our species.