Science Article

May 2000

Giraffes: animals that stand out in a crowd
By Lynn Hofland
http://creationism.org/articles/giraffes.htm

Giraffes truly do stand out in a crowd. At the zoo or in their habitat of Central Africa, they tower above other beasts, and are the second largest land animals alive today (the African elephant is the largest). The length of the giraffe's neck has intrigued observers down through the years. 'How did the giraffe get its long neck?', some ask.

On witnessing a 3-meter (10 foot) shoulder high giraffe stretch its 2.5 meter (8 foot) neck to its limit, and then add almost another foot with its long grasping tongue for that seemingly out of reach branch high in an acacia tree, some might believe that the stretching process drove the growth process for the giraffe's neck. But really, is a giraffe capable of adding anything to its stature?

If one feature did change, would it not affect the whole? Let's consider the giraffe.

The giraffe is a mammal, therefore much of its anatomy is similar to that of other mammals. Like most other mammals, the giraffe has seven neck bones. What if it did not have seven bones between the shoulder and the base of the skull? Man's short neck supports a perfectly balanced head in the erect posture with very little effort. The giraffe's huge head must be held aloft at all times. When standing, nearly half of its approximately 225 kilogram (500 pound) neck muscles are in tension. The amount of muscle required is directly related to the number of joints that must reduce the weight considerably and require less energy for survival. If the shortage of food drove the neck to change, would not the number of neck bones and joints be changeable also by such evolutionary process? Of course the problem with this design would be a loss of flexibility, and would severely increase breakability if the giraffes received a blow to the head or neck.

In the same respect, having a mega-jointed neck would require the exact opposite greater energy use and greater muscle mass to be supported. This would cause the giraffe's center of gravity to shift ahead of the front legs when the head is extended straight forward, causing the hind legs to come off the ground - assuming the front legs were strong enough. Seven neck bones is excellent design.

With the head being so high in the air, the huge heart of the giraffe must be capable of delivering sufficient oxygen rich blood three meters (10 feet) up to the brain. This would be a problem (involving too high blood pressure) when the giraffe has head down drinking water, would it not for a unique collection for reinforced artery walls, bypass and anti-pooling valves, a web of small blood vessels (the rete mirabile, or marvelous net') and pressure-sensing signals that keep adequate blood flow to the brain at just the right pressurers in its cardiovascular system', the giraffe is unique.'

GRAVITY SUITS

Equally marvelous is the fact the blood does not pool in the legs, and a giraffe does not bleed profusely if cut on the leg. The secret lies in an extremely tough skin and an inner fascia that prevents blood pooling. This skin combinaiton has been studied extensively by NASA scientist in their development of gravity-suits for astronauts. Equally helpful to prevent profuse bleeding is that all arteries and veins in the giraffe's legs are very internal.

The capillaries that reach the surface are extremely small, and the red blood cells are about one-third the size of their human counterparts, making capillary passage possible. I quickly becomes apparent that these unique facets of the giraffe are all interactive and interdependent with its long neck.

But there's more. The smaller red blood cells allow for more surface area and a higher and faster absorption of oxygen into the blood. This helps to retain adequate oxygen to all extremities, including the head.

The lungs work in conjunction with the heart to supply the giraffe with the necessary oxygen, but in a way that is unique to the giraffe. The giraffe's lungs are eight times the size of those of humans, and its respiratory rate is about one-third that of humans. Breathing more slowly is necessary in order to exchange the required large volume of air without causing windburn to the giraffe's rippled 3.6 meters (12 feet) of trachea. When the animal takes in a fresh breath, the oxygen depleated previous breath cannot be totally expelled. For the giraffe this problem is compounded by the long trachea that will retain more dead air than man can inhale in one breath. There must be enough lung volume to make this 'bad air' a small percentage of the total. This is a physics problem that the giraffe has solved.

As you can see, the giraffe's unique and marvelous design is ample testimony of the creator who is the master designer.

LYNN HOFLAND, B.S.E.E., is an Environmental Test Engineer at NASA Ames Research Center, Mountain View, California. He and his wife home-school their three children, and started "Stffneck Mini-stries" five years ago to provide a library of creationist material to other home schoolers.