The giraffe neck couldn't evolve without a special circulatory system (Talk.Origins)
A giraffe's heart must be quite large (it is over 24 lbs) to pump blood to the giraffe's head. A series of special one-way valves in the neck regulates blood flow, and there is a special net of elastic blood vessels at the base of the brain. Without these valves and elastic blood vessels, the blood pressure in the giraffe's head would be immense when it bends over, enough to cause brain damage. All of these features -- large heart, valves in the jugular vein, and wondernet of vessels -- must be in place simultaneously or the giraffe would die. They could not have evolved gradually.
- Davis, Percival and Dean H. Kenyon, 1989. Of Pandas and People: The Central Question of Biological Origins (2nd ed.). Dallas, TX: Haughton, pp. 69-72.
- Setterfield, Barry, 1998. Birds, beetles, and life.
This is a misrepresentation of the cited sources, For example Setterfield said “The giraffe's neck is a testimony to special design and planning,” not that it “could not have evolved gradually.” Setterfield is making a positive case for design, not a negative one against the possible evolution of the giraffe's neck. He is saying that design is the most reasonable explanation of the giraffe's neck, but not necessarily the only one.