I fail to see how natural selection can build any kind of new functionality.
New functionality in a design requires sacrificing a complex series of meanwhile useless steps before the new functionality works and becomes advantageous.
For example, if I want to upgrade a stationary chair to a wheelchair, there are many intermediate steps that must be done (which are not advantageous) before the added functionality becomes advantageous.
If a human being sits there and tries to intelligently assemble the wheelchair in such a way that it will be advantageous at each step, he will not be able to do it. it just doesn't work like this.
Can someone fill me in as to how this works and whether there have been experiments that demonstrate this, for example, having someone assemble a simple functional design with the limitation that every few step adds advantageous functionality.