Darwin wasn't the first to
suggest the theory of evolution—that all living things originate from
ancestral forms and that their distinguishable differences are due to
modifications in successive generations. But no one gave it more thought, or
provided more evidence for it, or more deeply ingrained the theory into our
collective consciousness than Charles Darwin. Today, researchers using the
genetic techniques of "evo devo" can trace the evolution of the
various kinds of organisms that Darwin fit into his "tree of life"
(here, from an 1837 notebook, his first such tree). As the geneticist Theodosius
Dobzhansky once wrote, "Nothing in biology makes sense except in the
light of evolution."