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David Attenborough's Rise of Animals: Triumph of the Vertebrates:

Why Warm Blood is Better Than Cold

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»Dawn of the Mammals

Why Warm Blood is Better Than Cold

Short | 03:11

Mammals didn't used to be at the top of the food chain. See how one key adaptation gave them a leg up on their reptilian contemporaries.

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A mass extinction rid the world of dinosaurs 65 million years ago. With the biggest players out of the picture, the world was up for grabs, and a new branch of vertebrate would eventually take over. Join David Attenborough as he charts the fascinating story of the mammals, from their origins as tiny nocturnal forest-dwellers to their explosion in diversity and domination. Through new fossil discoveries, we chart how and when our ancestors developed hair, placentas, and milk, and laid the foundations for the major mammal groups we see today.

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