Why Evolution Is True

by Jerry A. Coyne

Natural selection is not a master engineer, but a tinkerer. It doesn’t produce the absolute perfection achievable by a designer starting from scratch, but merely the best it can do with what it has to work with.

Likewise for all cases of extinction, which represent well over 99 percent of species that ever lived. (This, by the way, poses an enormous problem for theories of intelligent design (ID). It doesn’t seem so intelligent to design millions of species that are destined to go extinct, and then replace them with other, similar species, most of which will also vanish. ID supporters have never addressed this difficulty.)

Mutations are changes in traits that already exist; they almost never create brand-new features. This means that evolution must build a new species starting with the design of its ancestors. Evolution is like an architect who cannot design a building from scratch, but must build every new structure by adapting a preexisting building, keeping the structure habitable all the while.