Walking with Beasts

3.2 million years ago, Late Pliocene (Ethiopia) Filming location: South Africa, Ethiopia

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. However, it notes that although the Australopithecus looks human, it still only has the mind the size of a chimpanzee's. Some of the topics explored in the episode are the close social bonds among the tribe, how they use grooming as a means of communication, and how they work together to forage for food and to defend one another from attacks from such animals as an angry male Deinotherium, an ancestor of the modern elephant which they have to run from to avoid being crushed, and the feline predator Dinofelis. It touches upon how competing tribes of Australopithecus war among one another, although most of fighting is for show. It also explains the hierarchy in the tribe among the males (who are much larger than the females) and tells a story of how the dominating male is eventually overcome by another male, who wins the right to feed first at a carrion and to mate with the females. The main story tells of a young Australopithecus nicknamed Blue whose mother has been killed by malaria. He and his tribe are later forced to flee their homeland during a fight over a waterhole with a rival tribe. After a long journey in search of a new home, Blue fits into his tribe by causing them to scare off a hungry Dinofelis.

Animals: Australopithecus · Dinofelis · Deinotherium · Ancylotherium · Warthog · Rhinoceros · Jackal · Vulture · Zebra (carcass) · Ostrich

1 million years ago, Early Pleistocene (Paraguay) Filming location: Brazil

The fifth episode shows the strange fauna of the isolated continent of South America and explores the effects of the Great American Interchange, which had happened 1.5 million years earlier. Since South America had drifted apart from Antarctica 30 million years ago, many unique mammals had evolved, including the Doedicurus, an armored armadillo-like mammal with a cannon ball-sized spiked club on its tail; the Macrauchenia, a camel-like mammal with a long trunk; and the Megatherium, a giant ground sloth. Before the continents of South America and North America collided, a 10-foot-tall predatory terror bird called Phorusrhacos, had reigned as top predator. However, the great cats migrating from the north, soon displaced them as top predators. The episode focuses on a male Smilodon, a sabre-toothed cat, called Half Tooth, whose leadership of a pride is threatened by two males who are brothers and work together against him. The rival males ultimately chase off Half Tooth (actually Half Tooth backs off wisely without any serious injuries, feeling that the two males would be too strong for him), kill his cubs, and take over his pride. Next, the episode shows the Smilodon cats hunting down Macrauchenia and trying to protect the young from the two brothers (in vain). In the background, "terror birds" still hunt, but give way to the Smilodon. However, a Megatherium, who wanted to eat meat as diet supplement, charges the pride of Smilodon, in order to eat some of the carrion. In the process, the Megatherium kills the dominant rival male, enabling Half Tooth to return, kill the other male and reclaim his territory. A year later, his mate had another litter of cubs.

Animals: Smilodon · Phorusrhacos · Macrauchenia · Megatherium · Doedicurus

30,000 years ago, Late Pleistocene (Belgium) Filming location: Yukon

The sixth episode takes place during the last Ice Age of the late Pleistocene. It starts in the peak of the summer. The North Sea has become a grassy plain because the ice at the polar caps has caused the sea levels to drop significantly. Grazing on the plain are herds of woolly mammoths, saiga antelopes, and bison. A clan of Cro-Magnons (identified as humans) is also there spending the summer. The central focus of the episode is the migration of the herd of mammoths as they travel 400 kilometers from the North Sea to the Swiss Alps for the winter and then back again in the spring. As the mammoth herd migrates south, the episode shows two large deer, the Megaloceros, fighting for rights to a harem of females. As the male Megaloceros fight, a group of humans ambushes them and kills one. A mother mammoth and her baby are separated from the herd, but survive an encounter with a cave lion. When the herd of mammoths reaches the Swiss Alps, the mother and baby mammoth reunite with their herd. The episode also depicts a clan of Neanderthals, who have especially evolved to survive in the cold climate. One is charged by a woolly rhinoceros, but escapes, in part because of his stocky constitution. The climax of the episode is when the clan of Neanderthals attack the herd of mammoth as they turn back to the north. The Neanderthals are gifted hunters who are able to chase two mammoths off a cliff by using fire and spears, one of them being the matriarch of the herd. The episode ends in the Oxford University Museum of Natural History with people looking at various skeletons of some descendants of the animals featured in the series. The camera then pulls back through the roof of the museum until the whole world is visible. The narrator states that, "We have since built museums to celebrate the past, and spent decades studying prehistoric lives. And if all this has taught us anything, it is this: no species lasts forever."

Animals: Woolly mammoth · Megaloceros · Woolly rhinoceros · Cro-Magnon · Cave lion · Neanderthal · Saiga antelope · Grey wolf · Wisent