This instalment is the first of several to concentrate on mammals. The platypus and the echidna are the only mammals that lay eggs (in much the same manner of reptiles), and it is from such animals that others in the group evolved. Since mammals have warm blood and most have dense fur, they can hunt at night when temperatures drop. It is for this reason that they became more successful than their reptile ancestors, who needed to heat themselves externally. Much of the programme is devoted to marsupials (whose young are partially formed at birth) of which fossils have been found in the Americas dating back 60 million years. However, because of continental drift, this kind of mammal flourished in Australia. Examples shown include the quoll, the Tasmanian devil, the koala, the wombat and the largest marsupial, the red kangaroo. The thylacine was similar to a wolf but is now thought to be extinct.

Storyline: During experiments to find a cure for Alzheimer's disease, a genetically-enhanced chimpanzee uses its greater intelligence to lead other apes to freedom.

During experiments to find a cure for Alzheimer s disease, a genetically-enhanced chimpanzee uses its greater intelligence to lead other apes to freedom.

During experiments to find a cure for Alzheimer s disease, a genetically-enhanced chimpanzee uses its greater intelligence to lead other apes to freedom.

Storyline: During experiments to find a cure for Alzheimer's disease, a genetically-enhanced chimpanzee uses its greater intelligence to lead other apes to freedom.

During experiments to find a cure for Alzheimer's disease, a genetically-enhanced chimpanzee uses its greater intelligence to lead other apes to freedom.