Part one of two. Biologist Patrick Aryee explores how cats have evolved throughout the millennia, learning to thrive in inhospitable environments, as well as becoming the world's most popular pet. In the first edition there is spectacular footage of caracals jumping three metres to catch flying birds, and a rare Bornean bay cat, which was thought to have been extinct. Patrick finds out how tigers made the transition from South-east Asia's steamy jungles to the -40C temperatures of Siberia, and meets 'lion whisperer' Kevin Richardson