An organism is irreducibly complex if taking away some of its parts doesn't just make it work a little worse, but makes it not work at all.
An illustration of irreducible complexity is a mouse trap. A mouse trap consists of several elements: a flat platform, a spring, a trigger, an arm, and some cheese. A mouse trap with all of these elements will work well. A mouse trap that lacks any one of these elements, though, won't just not work well, it won't work at all.
If there is no platform to which the other elements can be attached, then the mouse can grab the cheese from the unassembled mouse trap with impunity. If there is no spring, then the mouse will set off the trap, but the arm won't snap down on it. If there is no trigger, then the mouse can grab the cheese without setting off the trap. If there is no arm, then it doesn't matter that the mouse sets off the trap. If there is no cheese, then the mouse won't go anywhere near the trap. To have a mouse trap that functions at all, then, you need every one of these elements; if you're missing any of them then it just won't work.
Evolution theory holds that we have evolved incrementally over time, gradually changing from one state that works to another state that works better. If evolution theory is true, therefore, then there must be a succession of states, each of which allows us to survive, through which we have evolved on an upward curve.
This, though, doesn't seem to be the case; we seem to be irreducibly complex. To illustrate (actual examples are a bit more complex than this): think of the organs that make human beings work, our hearts, lungs, stomachs, brains, etc. A human being that lacks any of these won't just have less survival value than one with all of them; it won't have any survival value at all. A human being without a heart is a dead human being, as is one without either lungs, or a stomach, or a brain. We therefore can't have incrementally acquired these things, first getting one, then another, and so on; we must have acquired them all at once. That, though, isn't evolution. Evolution is a gradual process.
Evolution, then, cannot explain the origin of irreducibly complex biological organisms. If (and that's a big "if") we are such organisms, then there must be more to how we got here than evolution.
Log in to comment