Not the first person to get this, but here's Darwin's 1837 sketch of a phylogenetic tree. (By Walt at Nola Tattoo.)
charles darwin tattoo
The tree of life... (darwin, evolution, science, biology, atheist, atheism) ..this is so beautiful...
My first Tattoo: Darwins first scribble of the tree of life out of his notebook and aditionally 4 Darwin Finches :)
Darwin's finches with their food! Large ground finch with prickly pear cactus, medium ground finch with tree buds and small seeds, and tool-using woodpecker finch with long horned beetle. Thanks Nathaniel!