Amid a celebration, a mystery: A fresh appeal has been launched to find a missing notebook that Charles Darwin may have used to write On the Origin of Species, which was published 150 years ago today. The journal records Darwin's observations in the Galapagos Island and Peru. Authorities believe it was stolen from the naturalist's former home at least 30 years ago.
"The Galapagos notebook is of outstanding value for the history of science," Darwin's great-great-grandson tells the BBC. "If Darwin had not posed the questions in that notebook, he might never have written On the Origin of Species."