Do drinking giraffes have headaches?
by Robert E. Kofahl, Ph.D.
Charles Darwin wrote in his Origin of Species that he had no difficulty in imagining that a long drought could have caused some hypothetical short-necked ancestors of the giraffe to stretch their necks continually higher to reach the diminishing supply of leaves. He had no fossil evidence, of course, for such an evolutionary history. He also apparently was not aware of certain problems peculiar to giraffes which make his easy assumption of giraffe evolution even more difficult to accept.
The giraffe heart is probably the most powerful in the animal kingdom, because about double normal pressure is required to pump blood up that long neck to the brain. But the brain is a very delicate structure which cannot stand high blood pressure. What happens when the giraffe bends down to take a drink? Does he ‘blow his mind’? Fortunately, three design features have been included in the giraffe to control this and related problems.
In the first place, the giraffe must spread his front legs apart in order to drink comfortably. This lowers the level of the heart somewhat and so reduces the difference in height from the heart to the head of the drinking animal. The result is that excess pressure in the brain is less than it would be if the legs were kept straight.
Second, the giraffe has in his jugular veins a series of one-way check valves which immediately close as the head is lowered, thus preventing blood from flowing back down into the brain.
But what of the blood flow through the carotid artery from the heart to the brain?
A third design feature is the ‘wonder net’, a spongy tissue filled with numerous small blood vessels located near the base of the brain. The arterial blood first flows through this net of vessels before it reaches the brain. It is believed that when the animal stoops to drink, the wonder net in some way controls the blood flow so that the full pressure is not exerted on the brain.
Scientists also believe that probably the cerebrospinal fluid which bathes the brain and spinal column produces a counter-pressure which prevents rupture or leakage from the brain capillaries. The effect is similar to that of a G-suit worn by fighter pilots and astronauts. The G-suit exerts pressure on the body and legs of the wearer under high acceleration and prevents blackout. Leakage from the capillaries in the giraffe’s legs, due to high blood pressure, is also probably prevented by a similar pressure of the tissue fluid outside the cells. In addition, the walls of the giraffe’s arteries are thicker than those in any other mammal.
Had Darwin known all these problems peculiar to giraffes, it surely would have given him a headache.
Some careful investigations and measurements of blood pressure have recently been made in live giraffes in action. However, the exact manner in which these various factors operate to enable the strange creature to live has still not been clearly demonstrated. Nevertheless, the giraffe is a great success. When he has finished his drink he stands up, the check valves open, the effects of the wonder net and the various counter-pressure mechanisms relax, and all is well. Not even a headache!
http://www.setterfield.org/essays/giraffe.html
http://creationwiki.org/(Talk.Origi...t_evolve_without_a_special_circulatory_system
That Troubling Laryngeal Nerve?
by Frank Sherwin, M.A.
The recurrent laryngeal nerve (RLN) in man is found branching off the tenth cranial nerve (vagus) in the chest cavity. The twelve cranial nerves are part of the beautifully designed autonomic nervous system (ANS) that controls involuntary body processes, including digestion, heart rate, and respiration. Evolutionists claim the Creator is a bad engineer, having the RLN dropping into the chest and looping around a ligament of the lung before going back up to the larynx (voice box). Evolutionist Michael Denton states, "The recurrent laryngeal nerve loops around the aorta and back up to the larynx instead of taking a more direct route."1 In other words, "Why not just have the nerve extend directly from the brain to the larynx?"
Before answering this, creationists are reminded of other past "bad design" arguments used by evolutionists that have since received good, scientific answers. Examples include the poorly designed thumb of the panda bear. The late S. J. Gould2 repeatedly cited this allegedly corrupt feature, but he ignored the fact that panda bears have been doing just fine with this supposedly inferior structure. (For a fascinating discussion of this "pseudo-thumb" see Nature 397:309.)
In past decades, evolutionists, such as Richard Dawkins, have maintained the retina of our eyes was actually "wired backward." If a Creator existed, He certainly would not have done it that way with photoreceptor cells oriented so their sensory ends are directed away from incident light. Today we hear virtually nothing about this allegedly imperfect manner of wiring. Why? Because scientists have shown our retinas are designed exactly the way they should be in order to receive photons (light) and direct the impulses via the optic nerves to the back of the brain where they are made into images. Indeed, if the eye was designed to Darwinist specifications, we would be blind. (See also:
http://www.trueorigin.org/retina.asp)
Why did the Creator design the loop of the RLN? To the secular biologist, it is both strange and unnecessary, basing these judgments on the corrupt philosophy of Darwinism (macroevolution). But creation scientists and medical doctors are investigating and have several ideas. There are branches of the RLN going above and below the larynx (both branch off the vagus) that would allow some preservation of function if either one is severed. The RLN passes tightly under the aorta (the large, main artery coming from the left ventricle of the heart). Perhaps variation in the diameter of the aorta could alter the function of the RLN.
Of course, the amazing and complex field of neuroanatomy and physiology itself is an affront to Darwinism. The origin (not the present operation) of life's amazing complexity is seemingly not within the reach of merely natural processes. Let the evolutionist explain the origin and gradual evolution of our 3-pound brain from "simple" life forms while the creationist continues to investigate the puzzling RLN route. I believe we will have our answer first.
Denton, Michael J., Nature's Destiny, Free Press, 1998, p. 260.
Gould, S. J., "The Panda's Thumb of Technology," Natural History, January 1987, p. 14.
Deluje sasavo ali mene vrat nikad ne boli
