How did the elephant get so big? Chris Packham explores the four-billion-year story of how a tiny cell evolved into complex, gentle giants.

How did the ostrich come to lay the biggest egg on Earth? Chris Packham explores the way reproduction has shaped life on Earth and the surprising evolutionary origins of sex, eggs and birds. It's a four billion year journey contained within a shell.

How did the bat get so hungry? Chris Packham explores how the drive to find food has shaped animal life. The origin of bums, guts, jaws and super-hearing.

How did the dolphin get so smart? Chris Packham explores the origins of senses, brains and intelligence, in an evolutionary odyssey that ventures from ocean to land and back again.

How did the horse become so fast? Chris Packham sets out on a slithering, swimming, sprinting odyssey that explores the evolutionary beginnings of animal movement and how it reached its peak in one of the most elegant and athletic animals on Earth: the horse.