Irreducible complexity is an argument against evolution. Evolution teaches the concept of the survival of the fittest. The more a creature’s physical and mental attributes enhance its chances of survival, the more likely it is able to live long enough to mate and pass on those helpful genetic traits to the next generation.
Macroevolution refers to giant changes in physical characteristics. The first fish that had little nubs to help it get food on land was healthier than the normal fish, and passed on those nubs to the next generation. Eventually, simple fins evolve into arms, hands, and fingers that can play Rachmaninoff on the piano. Microevolution refers to small changes. A bird with a slightly longer beak than its nest-mates is able to reach more bugs in the holes of trees and live a healthier, longer life. It therefore produces more offspring who also have longer beaks and live healthier, longer lives.
Irreducible complexity brings up those complex biological mechanisms that show no sign of evolution—micro or macro—because any simplification or alteration in their design would leave them useless for their specific purpose. In order for these mechanisms to have developed, several complex genetic changes would have had to occur simultaneously—an event that is inconsistent with evolution and mathematically nearly impossible. There are several biological systems that seem to be irreducibly complex.
Bacterial flagella: The most commonly mentioned is the flagella, or whip-like propulsion device, of bacteria. It consists of a drive shaft, bushing, a stator, a rotor, and a switch regulator. Despite claims by evolutionists, there has yet to be a functional theory as to how this nano-machine could have evolved from something more primitive.
Blood clotting: Blood clotting may be essential for animals, but it is not an inevitable result of the laws of physics. There is no law in physics that requires the clotting of blood. The mechanism by which blood clots, however, is so complex that mathematically it is extremely unlikely that it occurred spontaneously without divine intervention.
The eye: Although evolutionists have attempted to show how the eye could have evolved, the sheer complexity of the mechanism defies explanation. The retina actually interprets much of the input before it reaches the brain. The processors in the brain would have had to evolve parallel with yet independently of the development of the eye itself. Even the computer simulation of the evolution of the eye shows how only an intentional design could have resulted in such functionality.
Three characteristics identify an irreducibly complex system: did it have to happen (was it inevitable by the laws of physics?), did it happen by accident, and did an intelligent agent cause it to happen? Since these questions can’t be answered definitively, irreducible complexity is a game of statistics—what is the chance that this essential thing could have spontaneously developed by accident? In the case of irreducibly complex systems, that chance is mathematically negligible.
Irreducible complexity is not a watertight argument for the involvement of intelligence in the formation of biological systems. It’s possible that an irreducible system could be a simplification of a more complex one; a backpack can still hold things if you remove the straps, zipper, and exterior pockets. It’s also possible for a system to have evolved from another system with a different purpose—as any toddler with a wooden spoon and a collection of pans can attest.
Still, the Bible teaches:
For you formed my inward parts;
you knitted me together in my mother’s womb.
I praise you, for I am fearfully and wonderfully made.
Wonderful are your works;
my soul knows it very well.
My frame was not hidden from you,
when I was being made in secret,
intricately woven in the depths of the earth.
Your eyes saw my unformed substance;
in your book were written, every one of them,
the days that were formed for me,
when as yet there was none of them. Psalm 139:13-16