Original air date: 20 November 2002

Above is a graphical presentation of the episode, a more detailed text version of the timeline is below

Selected material
The most ancient mammals

In Australia there are the two most ancient mammals alive today, and the only two egg-laying ones. The left image shows Attenborough holding an aerial receiver to follow an echidna (centre) that had been fitted a transmitter. The only other egg laying mammal, the platypus, is on the right.
The platypus in its burrow

As BBC tend to do, they are using the latest technology (in this case an optical probe) to film the platypus inside its burrow. According to Attenborough no one knew what went on inside the burrow. With help from local scientists a burrow was located and a probe inserted for Attenborough (and camera team) to film the platypus (left) and a young (on the right).