This is the first part of the first episode on the series, Survival, which deals with how the earliest humans spread around the world, adapting and surviving against the odds.
The other episodes in the series are:
2 Age of Empire
3 The word and the sword
4 Into the light
5 Age of plunder
6 Revolution
7 Age of industry
8 Age of extremes
You can read the subtitles for the clip above here.
You can watch the remaining parts of the episode here and here.