Episode Title:Next of Kin.Episode Description:The fourth episode takes place in the Great Rift Valley in northeastern Africa of the late Pliocene. The climate has changed, and now great grasslands have replaced trees. The episode focuses around a tribe of small hominids known as Australopithecus, one of the first apes able to walk upright and a close ancestor to humans. The Australopithecus has evolved to walk upright so as to better maneuver the plains as well as the climb the trees.