"Years before Darwin developed the notion of natural selection as a force capable of generating exquisitely complex adaptations, he was struck by the fact that, given the results of geological dating, Creationism required a Creator who intervened piecemeal and repeatedly, over many millions of years, with no indication of any overall plan, and creating many organisms only to see them become extinct. At first a Creationist, Darwin considered this kind of repeated and undirected intervention so dubious that a purely natural explanation began to seem more appealing to him, and this eventually led him to consider natural selection.
Intelligent Design theory makes no attempt to analyze the character of the Designer from the data of the Designer's performance. It is merely concerned with accumulating examples suggesting that there is a Designer, and that Darwinism can be rejected --- and there the theory of Intelligent Design stops.
There are many cases where we don't know the path evolution actually might have taken. It's always possible to point to some adaptation, assert that it could not possibly have come about by accumulated gradual adjustments, and reiterate this assertion for as long as biologists have not come up with any specific evolutionary pathway.
However, this is to look at only half the evidence relevant to the design hypothesis. We also have to consider those many aspects of living organisms which appear, from a design point of view, to be botched and incompetent. If the Designer is so Intelligent, how come he keeps screwing up?
Examples of outrageously bad 'design' can usually be explained by the path evolution has taken. There really are cases where 'you can't get here from there', or at least it's too improbable. Since natural selection cannot look ahead and try a radically different approach to solving a particular problem, but always has to move by slow increments from something which has worked in the recent past, there will sometimes be cases where the outcome is just hoplelessly inefficient.
There are innumerable such examples. One is the fact that human babies naturally have to be born through the bone-enclosed pelvic opening. Untold billions of babies and their mothers have died in childbirth because of this elementary 'design flaw', which arose because humans are descended from animals that scampered on all fours. In many cases today, the birth opening which idiot nature failed to hit upon is provided by a surgeon, in a caesarian section. This saves the lives of millions, and in many more cases reduces brain damage to the infant or hours of discomfort to the mother. Any intelligent designer planning the human body from scratch would have installed a birth opening in the lower abdomen, where there is no tight constriction by bones. But natural selection could not accomplish this clear and obvious improvement, because there was no way to get 'there from here' by minute adjustments.
The human body is an exhibition of engineering disasters. The routing of the optic nerve through the front of the retina, so that there is a 'blind spot' in each eye, and the routing of the male testis around the ureter, when it would be so much simpler and more efficient to take a direct route, are other instances. These sorry failings do not contradict the proposition that many features of the human body display marvelous construction, sometimes far exceeding what could have been accomplished by human ingenuity. The two aspects exist side by side: dazzling sophistication and crude sloppiness. ID theory has no explanation to offer for the latter. Darwinism tells us to expect both. A striking example occuring in all mammals is the routing of the recurrent laryngeal nerve, which instead of going directly from the brain to the larynx, makes a completely pointless detour to loop around a lung ligament. In the giraffe, whose neck lengthened in the course of evolution, this nerve is twenty feet long, instead of the required one foot.
Why can't evolution itself take care of these problems? Why can't evolution create a new birth canal in humans, reroute the optic nerve into the back of the retina, or shorten the routes of the male ureter and the recurrent laryngeal nerve in the giraffe's neck? The answer is that once a highly complex 'basic plan' for an animal's body is in place, there are some improvements that cannot be accomplished by slight changes, but only by a radical redesign. There are indeed cases where you can't get here from there, and precisely in such cases, very obvious and simple improvements don't come about in nature, exactly as Darwinism leads us to expect.
Aside from cases of bad design, there are also aspects of the acutal process of evolution which are difficult to explain from a Design point of view. Why did life for at least a billion years consist of nothing but single-celled organisms such as bacteria? Why were all plants non-flowering until 130 million years ago, when flowering plants proliferated into thousands of diverse forms? This doesn't give the impression of a Designer who had any idea where he was going. Facts like these are puzzling if we assume there's a Designer. If there's no Designer, these facts fall naturally into place: they are what we would expect"
--- David R. Steele