Some claim evolution is just a theory, as if it were merely an opinion. The theory of evolution, like the theory of gravity, is a scientific fact. Evolution really happened. Accepting our kinship with all life on Earth is not only solid science. In my view, it’s also a soaring spiritual experience.

You can’t be a scientist if you’re uncomfortable with ignorance, because scientists live at the boundary between what is known and unknown in the cosmos….We’re always at the drawing board. If you’re not at the drawing board, you’re not making discoveries. You’re not a scientist; you’re something else.