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Kangaroo Rats; Multiple Nightmares
E. Norbert Smith, Ph.D.


While walking one morning in the beautiful desert of southern Arizona I realized how truly underrated are kangaroo rats and what a problem they must be for evolutionists. I was surrounded by ideal kangaroo rat habitat. Their burrows were obvious under each sagebrush bush and tracks filled sandy areas. Kangaroo rats are beautiful little brown and white animals with huge liquid brown eyes and a perky gait akin to Australian kangaroos. I often see them along the road late at night hopping merrily to and fro. They have given us much, yet we have returned little. They are not sold in pet stores. There are no kangaroo rat cartoon characters. Even the Tasmanian Devil is know to every school kid although its cartoon behavior is more akin to North America's wolverine. One sees Tasmanian devil toys, tee shirts and bumper stickers. I have yet to see one Kangaroo Rat toy or tee shirt. It seems kangaroo rats are good only for rattlesnake fodder! It is just not fair. Kangaroo rats are underrated. Let me explain.

One of their outstanding features is the number of facial muscles, yet this is never discussed in the media, partly I think because if flies in the face of some very old evolutionary thinking. Before the turn of the century it was widely publicized that of all mammals the primates had the most facial muscles. (We will not consider an elephant's trunk known even then to possess over 1,000 muscles.) In fact we primates do have over twice them number of facial muscles of most other animals. The large number of facial muscles is necessary for expression and thus is used in non-verbal communication. Emotions can be read on a face. We see few facial grimaces in sheep, dogs or cats that come close to the variety of facial expressions seen in man and ape. It was concluded that such communication was correlated with social behavior and intelligence and thus the maximum development and diversity of facial muscles were seen in the most intelligent animals. Man was seen as the glorious climax of evolution. Such simplistic thinking seldom withstands the test of time.

Remember these were the same crowd that for years taught the human brain was the largest and thus the most highly evolved of all animal brains, until someone discovered even the pelvic brain of certain dinosaurs (an enlargement that controls the hind legs) was much larger. How humiliating for the poor evolutionists! They quickly modified the definition to say the human has the largest brain of all animals as percentage of body mass and thus proof man was once again the most highly evolved. Again there were problems so the theory was once again modified to state the human brain is the most convoluted and thus has the greatest relative surface area. They have not yet recovered from the discovery that whales and porpoises have both larger and more convoluted brains, but that is another story.

Enter the kangaroo rat. Some years back a lowly graduate student discovered kangaroo rats have 42 pair of facial muscles! So much for the theory that intelligence is correlated with the number of facial muscles. But what could possibly be their function? Even the casual observer knows kangaroo rats do not appear to spend much time making faces at one another. Here again the unique kangaroo rats gait comes into play. They are often bipedal...hopping like their larger namesakes. But they do not hop very high. Night photography provided a striking discovery. As they hop their vibrissa (whiskers) are kept in contact with the surface of the desert! Thus the need for 42 pair of facial muscles the purpose of which is to provide tactile information about their environment as they hop about. What a deal! Of course there is never a word about how such a complex dynamic surface scanning system and its extraordinarily complex interpretation might have evolved. And some boast in evolution and proclaim loudly there is no God! I see God as loving variety and even with a sense of humor. The kangaroo rat certainly puts a fly in the evolutionist's ointment...once again. But there is much more.

As pets they are wonderful, for I have had plenty. (Of course this was before keeping such creatures was illegal!) They require little care and are delightful to watch. The eat little and require no drinking water. And unlike most other small mammals they are odor free. Yes, I meant to say they require no drinking water. This is perhaps their most outstanding feature. For years it was observed that most desert inhabitants require little or no water. Scientists worked out daily water budgets for a wide variety of animals including desert creatures. They would carefully measure all water intakes and collect urine and feces to determine the amount of water lost. Respiratory and skin loses were measured. As to the sources of water some biologists postulated dew. Obviously they had not spent much time camping in the desert for dew is a rarity and any animal depending on dew would not survive.

Other biologists suggested the importance of "pre-formed" water found naturally in the desert. Even desert plants contain high concentrations of water. Careful observation however clearly showed kangaroo rats could live without such "wet" plants. They can subsist quite nicely on a diet totally of dry seeds. They can get by on the metabolic water produced when carbohydrates are used producing carbon dioxide and water (see below). Examination of their urine was a biological bombshell. They can produce urine three times more salty than seawater. At first this seemed utterly impossible and caused rethinking of how mammalian kidneys operates. And it led directly to a better understanding of how we produce urine. Let me digress a bit and discuss human kidney function.

The human kidney provides a myriad of diverse functions including the regulation of blood acidity (pH balance), sodium, calcium, potassium, chlorine regulation and a variety of other important functions. And they regulate our water balance. Our kidneys are fascinating organs and their overall function is quite easy to understand. (Do not be misled. Many of the details of kidney function remain unknown.) We produce urine by three simple procedures: ultra-filtration, selective re-absorption and active secretion. Our blood acidity (pH is 7.4) is primarily regulated by our respiratory system. Unlike what most people think, our drive to breath is NOT to gain oxygen, but to rid the body of carbon dioxide. A secondary function is to obtain oxygen. For example if you ingest a coke (an acid) you will breath slightly, but measurably faster and deeper, to maintain your pH. If your pH drops from 7.4 to 7.3 you are dead or at least unconscious! The kidney provides a secondary or backup system for the maintenance of constant acidity. After ingesting that coke your urine will also become more acidic by the active secretion of hydrogen ions (cause of acidity) into the urine. Now for the other two ways urine is produced.

The functional unit of our kidneys is the nephron. There are about one million nephrons in each human kidney. The nephron starts with a leaky capillary called a glomerulus and a tube leading ultimately to the urinary bladder and outside. Ultra-filtration occurs in the glomerulus. Large quantities of blood are so filtered. Healthy human kidneys filter around 200 liters of urine (50 gallons) each day. Most is selectively reabsorbed yielding only about 1-2 liters of actual urine per day. Only the formed elements (blood cells and blood platelets) and large blood protein molecules are retained in the blood. EVERYTHING else is filtered out and must be reabsorbed or lost.

As the urine flows down the tubules various things are returned to the body as needed. Specific hormones control the re-absorption of specific molecules. For example, if your blood calcium is low calcium will be retained. If instead your blood calcium is high then calcium will be lost into the urine. Controlling hormones here are calcitonin from the thyroid and parathyroid hormone. The same is true for a large variety of other minerals including sodium. Surprisingly, the biological gain for the regulation of sodium has known to be infinity for decades. This is why physiologists have long laughed at medical doctors for telling people with hypertension to reduce their salt intake. Such reduction only produces unnecessary stress for it will have absolutely no lasting effect on the amount of sodium in the body or blood volume or on blood pressure. Since the gain is infinite a reduction of say one gram of salt per day will result in EXACTLY one gram LESS salt in the urine. Many doctors are finally recognizing this long known fact although the American Heart Association is still in the dark.

Essential and needed vitamins and amino acids and everything else your body needs is selective reabsorbed. So is water. The hormone ADH from the pituitary gland near the brain tightly regulates water balance. Without ADH 30-50 gallons of urine is lost EACH DAY. Alcohol is diuretic because it interferes with the release of ADH. Coffee is diuretic because it competes with the ADH receptor sites in the kidney. Thanks to the kangaroo rat we understand that much of the water is reabsorbed in a part of the nephron tubule called the Loop of Henley. For years no one understood the function of this important part of the kidney. Enter Kangaroo rats again. After it was discovered they can live on metabolic water alone and could produce urine three times as salty as sea water their kidneys were studied. Metabolic water is the water always produced when sugar is used as an energy source. Water and carbon dioxide are end products and it is this water alone than kangaroo rats can use to survive. This is possible because they greatly reduce the amount of water lost in urine. It was discovered the Loop of Henley of kangaroo rates was nearly three times longer than in the human. Farther studies showed the primary function to be water retention. Thus understanding kidney function in kangaroo rats led directly to understanding of how the human Loop of Henley functions. Such is often the case. The human can do lots of things (physiologically speaking) but cannot do any of them particularly well. It is often when we study extreme animal forms...those living on the physiological edge so to speak...that we better understand human function. Rattlesnakes can live up to 2 years without food or water. Parasitic ticks can survive five years with neither blood nor water! More examples another time. See why I love Zoology?

Another point must be made. Once again the evolutionists have jumped on the seemingly odd method of urine production and used it, as proof there is no God of Creation of if there is then He is but a fool. Yes, I have seen this in textbooks and heard it from medical school professors. As was seen with the human eye such an argument is illogical. Remember the human kidney functions flawlessly...consider sodium regulation! To point to it in ridicule is unabashed arrogance and ignorance on the part of the evolutionist. The evolutionists say that throwing away everything in the blood only to return it later is foolish and a waste of resources. Yet such proclamation reveals only their foolishness and shallowness of mind. We all know it is proper kidney function that also removes medicine from our bodies. Drug dosage to a person with diminished renal function must be reduced to avoid toxic drug levels. So it is with natural toxins and recreational drugs. Only by throwing away everything and returning what is needed can the body rid itself of such dangerous materials. Kidney anatomy and function is evidence of profound design. And Design requires a Designer. And I know and worship that Designer. It is indeed the evolutionist that is grasping...and always missing the obvious. There is a God of Creation for those that will but see.

I praise you because I am fearfully and wonderfully made; your works are wonderful, I know that full well. (Ps 139:14)

It is because the Kangaroo rat can produce urine three times more salty that they can survive in the desert southwest. Humans can only produce urine slightly more salty than seawater. Of course we have all seen the movies and might wonder then why we cannot survive with seawater. The answer is that the third most abundant salt in seawater is magnesium, which causes excessive water loss from diarrhea. We have learned much from the kangaroo rat and no doubt much remains to be learned. What do you think while walking in the desert home of the kangaroo rat? I think of their all-wise Creator and lift joyous praises to Him.