Walking with Cavemen episode guide

Episode four: The Survivors

Nearly half a million years ago, the most advanced human yet roams Europe. Strong and powerful, Homo heidelbergensis are fierce hunters, use sophisticated tools and live in close-knit family groups.

They look and behave in a very human way - yet something is missing. In 'The Survivors', the final programme in the series, we follow three brothers on a hunt. When one brother is injured his distraught family spend most of the night trying to keep him alive.

	Homo heidelbergensis

Yet in the morning, the hunter is dead and his family have gone, leaving him where he died. There is no ceremony and no looking back. Heidelbergensis can only see the world as it is. They cannot, for example, think of a life after death, for they lack the one thing that makes us human - a modern imagination.

Heidelbergensis are the departure point for the last leg of the journey towards modern humans. Over 200,000 years they become split into two populations by extremes of weather and environment and evolve separately into two very different species.

In the North are the Neanderthals, whose physical power and resilience is the key to surviving in ice age Northern Europe. In one of the most inhospitable environments ever, a small group of Neanderthal are finding things tough.

The leader's partner is expecting her first child, and the men must travel far to find food. If they're unsuccessful, the group will have to move on - a perilous journey for the near full-term mum. In their world, being strong and tough is the key to survival. If the going gets tough, they just fight back harder.

In the South the other descendants of heidelbergensis, are finding the going even harder. About 140,000 years ago, Africa is in the grip of a devastating drought, and something remarkable has happened to the descendants of heidelbergensis who live there. The combination of environment and chance has bred in them a unique ability that will change the course of human history.

They have developed a mind capable of imagination. For the first time on E arth there is a creature capable of understanding and anticipating possibilities, with the gift of abstract thought. It very possibly saves them from the brink of extinction.

Although the Neanderthals were unbeatable for a quarter of a million years, it will be this small band of southern survivors, perhaps numbering just a few tens of thousands, who will come to dominate the world and be known as Homo sapiens.

Next: The science of episode four