A complete sub-fossilised elephant bird egg sits next to a chicken's egg, in Christie's auction house on March 27, 2013 in London, England. The elephant bird egg is expected to fetch 30,000 GBP when it features in Christie's “Travel, Science and Natural History” sale, which is to be held on April 24, 2013 in London. (Photo by Oli Scarff)

An employee at Christie's auction house examines an Enigma cipher machine on March 27, 2013 in London, England. The Enigma machine is expected to fetch 60,000 GBP when it features in Christie's “Travel, Science and Natural History” sale, which is to be held on April 24, 2013 in London. (Photo by Oli Scarff)

A rare fragment from a dodo's femur bone at Christie's auction house on March 27, 2013 in London, England. The extinct bird's bone is expected to fetch 15,000 GBP when it features in Christie's “Travel, Science and Natural History” sale, which is to be held on April 24, 2013 in London. It is believed to be the first dodo bone that has come to auction since 1934. (Photo by Oli Scarff)