Can we make a picture of history? Charles Darwin recognized that all the different species on Earth share a common ancestry, having branched apart over millions of years. He pictured the history of life as a tree, as he sketched here in one of his notebooks. He later published a more formal illustration of the tree of life–or at least the branching of evolution–in the Origin of Species. Later scientists put actual names to the branches. They proposed that birds and crocodiles share a close common ancestry, for example, based on traits they share in common in their skeleton and skin. Later studies–including comparisons of DNA–supported many of those relationships. Today scientists are comparing entire genomes in order to illuminate