Irreversible complexity is a term referring to the fact that certain structures (such as the human
eye) are so complex, that it is incomprehensible to imagine how they could have evolved by
gradual changes over time: the complexity cannot be reversed back to simplicity. This is true
of other complex biological structures and is one of the arguments of the Intelligent Design
movement. This organisation isn't Christian based, it simply states that design in the Universe
suggests a Creator.
At the back of the human eye is the retina, which is less than one square inch yet contains
over 137,000,000 light sensitive cells all connected to your brain.
"It would take 100 years of Cray [super computer] time to simulate what takes place in your
eye many times every second" Reverse Engineering the Brain, 1985.
The blood cells are in front of the retina in the human eye to act as a last line of defence
against UV light. In an octopus they are behind the retina, which makes the eye more
effective as the water filters out the UV, so their eyes are protected by their environment, in
contrast to humans. How did one type of eye evolve into the other?
Another example of Irreversible complexity and the eye is the owl, which has a cylinder
shaped eyeball that cannot rotate in its socket. This is why it has to move its whole head to
look in different directions. How did this evolve? And how did it see when it was part way
between a sphere and cylindrical shape?
Psalm 94:9 "Does he who implanted the ear not hear? Does he who formed the eye not see?"