Since the dawn of time, roughly 99 percent of all species have become extinct. In order to survive, all creatures, including man, must treat life as a battlefield and master the natural weapons and defences that they have evolved: Tyrannosaurus Rex's 13-inch canines; the gecko’s Velcro-like toe pads; the bald eagle’s telescopic vision capable of spotting a hare a mile away.

How did these attributes, each unique to the organism itself, appear? Certainly not arbitrarily. They evolved for a common reason - to give these animals a critical edge in interspecies warfare, and to ensure the survival of the individual’s genes into the next generation. To evolve is to survive.

In this programme, we unpeel the layers of mystery surrounding the skin. It makes up 16% of your body weight, is the largest organ in the human body, allows birds to fly, mammals to nurse their young, and provides a lifelong defence against predators and parasites alike. But what exactly is it?

From the delicate membranes that encased the earliest animals to the leathery hides that protected the dinosaurs, this episode looks at how skin has changed and adapted to virtually any challenge it has faced throughout history.