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The Giant Claw
The narrator reveals that the world's climate is starting to deteriorate, bringing on an ice age. This means all animals, even the mighty Woolly mammoth are struggling. One of the herd falls through a pond concealed by ice. Her sisters comfort her, and in the morning the scavengers gather. The herd then have no choice but to leave their fallen sister to prepare for the coming Ice Age winter. The narrator also reveals that so much water is frozen at the poles, causing sea levels to drop. A vast Ice Age grassland, which today is the North Sea, supports an array of mammals including a herd of mammoths. Also residing on the plains in summer is a new creature: Human.
Despite having no physical adaptations for the cold, they wear animal hides to keep warm. The episode's main focus is the mammoth's 400 kilometer migration to the Alps and back in the spring. Meanwhile, two Megaloceros are fighting for a harem of females, but are then ambushed by the humans who kill one of the males. As the mammoths migrate, one of the herd and her six month old calf are separated and stalked by a Cave Lion, but survive.
Upon reaching the Alps, the mother and calf are reunited with the herd. Here in the valleys, one of the herd gives birth to a female calf. The episode also focuses on the Neanderthal, who, despite being built for the cold, is struggling as a result of the Ice Age. One of them is attacked by a Woolly Rhinoceros, but survives because of his shorter stature and thicker bones.
As the mammoths migrate back to the plains, they come into Neanderthal territory. The migration is important because they are risking their lives to hunt the beasts. They wait for nightfall and ambush the herd using fire. Two members, one of which is the matriarch, die in the attack. The Neanderthals are revealed to be supreme hunters, but they have an Achilles heel: they don't cope with change well. The narrator reveals in 2,000 years, they'll vanish. Back on the plains, the matriarch's sister leads her herd into the future. The narrator reveals mammoths will survive for 24,000 years until the plains they depend on will vanish. The humans, have a different story: they can cope with change when it comes, because of their adaptability and resourcefulness. The scene then changes to the Oxford Museum and the narrator reveals that "If all this has taught is anything, it's this: no species lasts forever."