Without water, a human can only survive for about 100 hours. But there’s a creature so resilient that it can go without it for decades. This 1-millimeter animal can survive both the hottest and coldest environments on earth, and can even withstand high levels of radiation. Thomas Boothby introduces us to the tardigrade, one of the toughest creatures on Earth.
When did we start riding horses? When did dogs become man's best friend? Answering questions like these help us understand our impact on other species' evolutionary journeys - a crucial step toward ensuring our survival doesn't necessarily come at the expense of their own.
This episode continues the study of mammals, and particularly those whose young gestate inside their bodies. Attenborough asks why these have become so varied and tries to discover the common theme that links them. Examples of primitive mammals that are still alive today include the treeshrew, the desman and the star-nosed mole. Insect eaters vary enormously from the aardvark, giant anteater and pangolin to those to which much of this programme is devoted: the bats, of which there are nearly 1,000 different species. These took to flying at night, and its possible that they evolved from treeshrews that jumped from tree to tree, in much the same way as a flying squirrel.