S4E5:Incredible Shells

8 Mar 201722 minTV-G

The shells of birds and tortoises have proved to be evolutionary winners. In this intriguing natural history documentary, David Attenborough discovers that the ostrich egg is so strong it's possible for a person to stand on it without breaking. So, how does the chick break out of this fortress? The tortoise shell was a mystery until it was revealed that it offers a lot more than just protection.