mousetrap is composed of five integral parts; the platform to which
everything is attached, the hammer which does the dirty work, the spring
which provides the force, the holding bar to keep the hammer in tension, and
finally the catch to keep the holding bar in tenuous position.
any one of these parts and the mousetrap is not just less efficient, it cease
to function at all. All five parts are necessary. You canít build a mousetrap
by natural selection by adding one piece at a time because it has no function
to select until all five parts are together.