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If bats were prettier to look at, we might appreciate their amazing talents more. The fact is that bats exhibit some astonishing design features which our engineers and technologists really envy. Traditionally scientists have grouped bats according to their food preferences. There are the fruit bats with good eyesight, the insect consuming, echolocating bats and the vampire or blood consuming bats. Further research has revealed how amazingly these animals are designed for their life styles. Such studies have also revealed that the old fashioned ways of categorizing the creatures according to lifestyle and physical appearance do not really work. This has had some serious implications for ideas concerning whether Darwinian evolution could ever work or not. 

The three species of vampire bats all live in the Americas. These ugly looking creatures need blood meals to live. Obviously they need to find a blood vessel in a victim that will allow blood to flow freely. This is not the easiest of tasks, but vampire bats have a special design feature which allows them to find good blood sources. In their upper lip and modified noseleaf, they have special nerve endings which are more sensitive than most nerves to body heat. These special tissues in the face allow them to find hot spots on the bodies of their victims. Here the blood vessels are located close to the surface. The bat nips the skin with his teeth in order to drink the flowing blood.

Many animals of course display normal heat receptors all over the body. These receptors are designed to respond to heat that is dangerous to the health of the creature. This applies to vampire bats as well. However in some nerves in the face of vampire bats, the nerves instead respond to a heat source which is much lower, about 30 degrees C. This protein receptor in the heat sensing nerves is unique to vampire bats and the way that this new sensor works is really astonishing.

There is a gene which scientists label Trpv1 which is found in all nerve cells sensitive to heat. This includes nerve cells all over the bodies of bats. In the case of the special nerve endings in vampire bat faces, the gene is the same. However those cells express an alternative form of the message derived from the gene. Into the blue print to build the protein (i.e. the information copied from the DNA molecule), a tiny piece of genetic information only 23 base pairs long is spliced. That tiny insert causes the construction of the protein to end somewhat prematurely, resulting in a molecule that lacks the last 62 amino acids. This is a very minimal difference in a large protein molecule, but that is what allows these cells to respond to the temperature range of hot spots in a victim’s body.

In the genetic code, base pairs are like rungs along the DNA molecule’s spiral length. Each rung also represents one of four choices of letter. Three letters or rungs in a row, code for an amino acid. In a protein molecule there might be 1000 amino acids or more. Thus the 23 base pair insertion in the case of the vampire bat protein, would only code for 7 amino acids. Yet this tiny insertion changes the whole character of the protein and this change allows for a whole different life style for the creature. Moreover this changed expression of the protein happens only in the appropriate nerve cells in the bat’s face, not anywhere else in the body.

Since the ability by bats to detect infrared radiation (heat) is so different from in snakes, scientists consider that there is no evolutionary connection between the two designs. Either each appeared as a spontaneous or novel feature, however complicated, or each was separately designed in its entirety.

It is the engineering triumph of echolocation (like sonar) however which really commands our attention. This system is truly complicated with many features that must work precisely. The bat must produce powerful ultrasonic signals which will bounce off objects and travel back as echoes. The creature must know the mathematic characteristics of the sound emitted in order to be able to compare it with the echo. The echo will be much softer, so the creature must be able to hear the incoming signal. Often the tempo of sounds emitted will include intervals between notes so that the incoming echoes can be heard. The bat must be able to judge its own position and speed relative to the returning echo which indicates the position and speed of the target object. This ability requires special mathematical programs in the brain to calculate the differences in speed and constantly changing location.

As far as the bats themselves are concerned, one might imagine that the echolocating bats would represent a cluster of creatures with other features in common. Even when the echolocating system is similar however, there are bats which seem closer in their genetics to the fruit bats. In addition, one fruit bat echolocates by means of tongue clicks instead of noise from the larynx. Does this represent a separate group too?

When one considers echolocation, scientists now declare that this complex capability arose spontaneously at least seven or eight times.  We see similar fancy systems in whales, bats, shrews, tenrecs (hedgehog like mammal native to Madagascar) as well as in oilbirds and cave swiftlets (another bird.)  And the ability to detect infrared radiation arose, scientists now declare, twice independently in snakes and once independently in bats. Scientists use the word “convergence” to cover situations where descent with modification is not a convincing explanation for the source of the feature. Thus convergence means separate appearance for no obvious cause. The alternative explanation for these situations of course is separate designs. God used his tool kit of wonderful design features as he saw fit, conferring them on similar or very different creatures for our interest and delight.

Recently scientists have discovered that the ability of bats to sense their environment is even more sensitive than previously imagined. In 2010, a team of scientists reported that some echolocating bats can control the width of the ultrasonic beam which they emit. The subject of this study involved bats that release sounds from their larynx, which is by far the most common method. More recently, another team investigated whether the tongue clicking Egyptian fruit bats are similarly versatile in their ability to respond to variation in the environment. This team found that Egyptian fruit bats simultaneously direct one beam of sound to the left and another to the right. They do this by aiming consecutive clicks in opposite directions.  As the environment becomes more cluttered with objects, the angle between the two beams of sound becomes wider (and the beam thus broader).  This enables the animal to focus on a particular object while paying less attention to other distracting structures in the environment. Also as the bat closes in on his target, the beam becomes broader and the sound more intense. This degree of sophistication in this echolocating system is a surprise to everyone. 

Many scientists claim that biochemical details from DNA sequencing confirm ideas about descent with modification which were developed over many years from anatomical comparisons.  The molecular details however have turned upside down ideas about evolutionary relationships (descent with modification).  Often we hear about “convergence”  or separate appearance of highly complicated features. It was not convincing when the argument was for the spontaneous appearance of even one complex system, but to suggest that it could happen multiple times, really strains credulity! What these amazing designs really demonstrate is the choices of an awesome Creator!

References:  Nature Jan 13/00 pp. 188-192; Feb. 18/10 pp. 939-942; Apr 15/10 pp. 1006-1011; Aug 4/11 pp. 88-91; PLoS Biol. September 13/11.

 


Margaret Helder
January 2012

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