Sir David Attenborough examines the mysteries behind some of nature's most fascinating creatures and plants.

How can the skin of two very different animals help them live long and healthy lives? Both the elephant and the tiny mole start their lives looking old and wrinkly and live to a great age, but the reason for their impressive longevity might be to do with their wrinkly skin.

Vikings once sold the spiral tusks of the narwhal as unicorn horns. Today, we are beginning to unravel the true nature of the narwhal's tusk and the reason for its spiral shape. The spiral is also vital to the lives of snails, allowing them to leave the sea and conquer land. Show less