Incredible Shells (S04E05)

David Attenborough explores two remarkable examples of evolutionary success: the bird's egg and the tortoise's tough shell. Remarkably, an ostrich egg is so robust that a person can stand on it without causing any damage—what strategies does the chick employ to escape this formidable barrier? The development of the tortoise shell has long puzzled scientists, revealing that this bony structure provides much more than mere defense.