Some animals have an extraordinary ability to find their way. The dung beetle, an insect revered by ancient Egyptians, uses the sun, the moon and even the Milky Way to move its prized ball of dung in the right direction. Pigeons are often considered feeble birdbrains, but they have incredible memories that can recall several complex travel routes with amazing accuracy and they even use man-made roads and hedgerows to find the quickest way home.
In episode three, Fortey looks at the Ice Age. 2.8 million years ago - triggered by slight changes in the Earth's orbit around the sun and shifts in its ocean currents - the world began to cool. Within a few thousand years much of the planet was shrouded in a dense cloak of ice that would come and go until only 10,000 years ago. We call this age of ice - the Pleistocene Age - and it transformed the hierarchy of nature. This is the story of how a few specialist species that evolved to live in the biting cold survived into the present day.
The documentary series reveals the extraordinary riches and wonders of the Polar Regions that have kept people visiting them for thousands of years. Today, their survival relies on a combination of ancient wisdom and cutting-edge science. Most Arctic people live in Siberia, either in cities like Norilsk - the coldest city on earth - or out on the tundra, where tribes like the Dogan survive by herding reindeer, using them to drag their homes behind them. On the coast, traditional people still hunt walrus from open boats - it is dangerous work, but one big walrus will feed a family for weeks. Settlers are drawn to the Arctic by its abundant minerals; the Danish Armed Forces maintain their claim to Greenland's mineral wealth with an epic dog sled patrol, covering 2,000 miles through the winter. Above, the spectacular northern lights can disrupt power supplies so scientists monitor it constantly, firing rockets into it to release a cloud of glowing smoke 100 kilometres high. In contrast, Antarctica is so remote and cold that it was only a century ago that the first people explored the continent. Captain Scott's hut still stands as a memorial to these men. Science is now the only significant human activity allowed; robot submarines are sent deep beneath the ice in search of new life-forms, which may also be found in a labyrinth of ice caves high up on an active volcano. Above, colossal balloons are launched into the purest air on earth to detect cosmic rays. At the South Pole there is a research base designed to withstand the world's most extreme winters. Cut off from the outside world for six months, the base is totally self-sufficient, even boasting a greenhouse.