The evolution of animal genitalia

Genitals are the fastest-evolving organs in the animal kingdom. But why is this so? And what's the point of having decorative private parts? Menno Schilthuizen explains how the evolutionary biology of nature's nether regions uncovers a hidden world of seduction, conflict, and rivalry. [Directed by Mette Ilene Holmriis, narrated by Adrian Dannatt, music by Wonder Boy Audio].