He has granted you from all that you ask Him. Were you to attempt to count God’s blessings, you could not compute them. But for sure, humankind is much prone to wrongdoing (sins and errors of judgment) and to ingratitude. (Ibrahim 14:34)

Today a large part of modern science focuses on understanding the human body. Researchers working on life sciences hope that one day the secrets of every single detail that make us human will be revealed. Every year billions of dollars are spent by scientific institutions on learning more about us. Actually this fact by itself is enough to suggest how little control we have over things happening in our bodies, and we know even less about the mechanisms of moving, touching, speaking, seeing, or hearing, and so on.

As a scientist, I really cannot guess whether life scientists will ever be able to learn enough to solve the puzzles of the human body, but I feel a lack of satisfaction when the knowledge we have gained from scientific discoveries is compared with what is unknown. In my opinion this is why one of the most intelligent physicists in history, the Nobel laureate Richard Feynman, once said, “I was born not knowing, and have only had a little time to change that here and there” [1]. My understanding is that such a conclusion must be inevitable if the primitive knowledge given to us by modern sciences is not interpreted in the light of a far superior logic that is meant to explain the whole creation. In that sense, I believe that we have to consider every single detail in creation as a vital part of the whole in order not to feel lost before the grand picture of this masterpiece.

Last year, in a seminar at Osaka University Graduate School for Frontier BioSciences, I was thrilled to hear Professor Keichi Namba say, “Japan’s fastest supercomputer dissipates more than billion times the power dissipated by a fly’s brain, yet it is not able to simulate the brain of such a tiny animal.” This worked as a wakening call or a reminder for me to think again about the magnificent arts of the Creator. In particular, I wanted to revise my research on a hearing-related protein from a new perspective, rather than using the mechanical attitude that is followed most of the time.

This article is an attempt to explain an amazing mechanism in our ears that enables us to hear the faintest whispers. A mechanism that is switched off at loud cries to protect us from disturbing noises, yet amplified to make the softest sounds audible. Before starting to explain the basic anatomy of the human ear, I should mention that today the ear’s active amplification mechanism is still being investigated in research centers by biologists and physicists together.

How do we hear? What is happening in the inner ear?

Findings from the last century have shown that our ears are not just simple receivers as we had imagined. In 1979, David Kemp of University College, London discovered that mammalian ears can also emit sound vibrations. By placing a very sensitive microphone close to the eardrum he could detect whistles, implying that there is a source of vibration within the ear [2]. However, before trying to explain the cause of vibrations in the ears, we have to go over the mechanism of hearing briefly: The delicate design of the outer ear, the tympanic membrane (eardrum), and the tiny bones (malleus, incus and stapes) enables to collect sound waves traveling in the medium and transfer them to the inner ear (Figure 1a). In the inner ear the sound waves are sorted according to their frequency and amplitudes and then converted into electrical signals which can be transported to the brain via nerves. At the onset of this process the sound waves are transformed into standing waves on the basilar membrane which is laid along the organ resembling a snail, the cochlea (Figure 1b). The frequency of the incoming sound wave determines the positions of the distortions along the cochlea: High pitches create vibrations at the basal end of the cochlea (i.e. adjacent to the middle ear) whereas low frequencies vibrate closer to the apical end (Figure 1c) where the cochlea gets narrower. This geometry helps our ears to act as a frequency analyzer.

The efferent and afferent nerves that connect the ear to the central nervous system are attached to the organ of Corti, which is situated right next to the basilar membrane, extending over the cochlea. In other words, Corti is the sense organ of hearing, converting the motion of the basilar membrane into electrical signals that are conducted to the brain via neuronal cells [3]. The organ of Corti is also lined with multiple rows of sensory hair cells.

The hair cells of the organ of Corti

Corti is decorated with two different sets of sensory cells: single row of inner hair cells (IHCs) accompanied with 3–4 rows of outer hair cells (OHCs), both spanning the whole cochlear tube (Figure 2a). They are called “hair cells” because both IHCs and OHCs have typical bundles of stereocilia that contain mechanosensitive ion channels (Figure 2b).

The major function of IHCs is to detect the sound waves and then convert them into equivalent electrical signals that are to be interpreted by the brain. When the basilar membrane is perturbed by the incoming sound waves, the IHCs found in that region sense this activity by the movement of their hair bundles (bundles of stereocilia). The hair bundles of IHCs deflect and re-align as the basilar membrane moves up and down (Figure 3). We should note that this is an amazingly sensitive process such that deflections of the stereocilia on the order of a few nanometers (one millionth of a millimeter) can be detected and converted into nerve signals by the IHCs [4].

However, this by itself is not sufficient for hearing; no matter how effective IHCs work, the fluid that fills the cochlear tube is a threat to the sound waves traveling in the inner ear. In 1948, a young astrophysicist named Thomas Gold was the first person who has pointed out that the fluidic nature of the cochlea would dampen the sound vibrations and make them too weak to be detected by IHCs. He has concluded that an inherent vibration amplification mechanism is necessary in order to overcome such a problem [5]. Unfortunately, Gold’s statements were overlooked by the physiologists of his time who had performed their hearing related experiments on dead cochleas.

Gold’s predictions were justified around ten years later by William Rhode, a physiologist from University of Wisconsin, who has shown that the vibrations of the basilar membrane in live tissue samples are stronger than anticipated [6]. In the present day the existence of an amplification mechanism within a live cochlea is a well accepted fact. The only disagreement among scientists is about how the mechanism of the amplification works. Several scientific laboratories have reported different experiments performed on the organ of Corti and they have proposed different models. At the center of one of these models is prestin, a membrane protein which is not found in any cell but OHCs in the human body.

Electro-motile outer hair cells and prestin

In 1985, the distinctive properties of OHCs were first discovered by William Brownell, a University of Geneva neuroscientist, who has shown that these cells can convert electrical signals into motion: A phenomenon called electromotility. Electromotile OHCs can elongate or shrink in response to electrical charge density changes in their membranes. About a decade ago Peter Dallos and co-workers from Northwestern University in Chicago discovered a membrane protein, unique to OHCs, that can respond to electrical signals [3]. The Dallos group coined the name “prestin” for this protein in an analogy with the musical term “presto” (quickly) due to its rapid response to electrical signals. Various kinds of mammalian cells genetically engineered to produce prestin at their membranes displayed the electromotile responses that are very similar to OHCs.

According to Peter Dallos prestin protein works as a tiny machine which is a crucial element for cochlear amplification [7]. His theory is verified by recent studies which show that cochlear sensitivity in mice decreases hundredfold when prestin activity is disrupted by genetic means [8]. As the sound waves reach the inner ear, prestin-driven electromotility enables the OHCs to move like pistons. The piston movement in phase with the basilar membrane motion amplifies the vibrations and makes them stronger for IHC detection (Figure 4a,b). The prestin-driven vibrations were what Thomas Gold proposed and David Kemp had detected so many years ago. However, scientists are still searching and learning new things about this nanometer scale machine. One of the discoveries showed that prestin can adjust itself according to the amplitude of the incoming sound waves: Basically, the amplification is stronger when the sound waves are hard to hear but gets weaker as the volume increases.

Up to this point, we have briefly explained how the amplification mechanism of hearing in mammals works. Unfortunately, even though it took decades of research for scientists to discover and define the active nature of the mammalian ear, this explanation highlights only a minuscule part of the whole picture. That is why we are still incapable of curing most hearing problems. For example, hearing loss due to slightly disturbed hair cells with damaged stereocilia turns out to be chronic (Figure 5). The medical treatments we have to hand are too primitive to mend such delicate structures. Moreover, hearing aids made by today’s technology are not nearly as effective and functional as needed.

On the other hand, the delicacy of the hair cells and the limited control scientists have over them are not the only lessons we have learned from research on the inner ear. We cannot overlook the other messages attached to the research on the grounds that the time given to us is just too short to comprehend. It is an undeniable fact that the sense of hearing is designed in the best way to serve human beings. The different characteristics of hearing amplification at different sound levels make life much easier for us: Prestin-driven hearing is most effective when the sound waves are weak and harder to hear. This way the incoming sound waves are amplified enabling us to hear the faintest whispers. However, as the sound strength increases, the prestin-driven amplification gradually gets weaker and finally diminishes after a point to make sure that loud noises are less disturbing and hazardous for us. In my opinion, this amazing quality of a tiny protein found in our ears is one of the pieces of evidence that remind us of the necessity of pondering the favors of our Creator. Qur’anic verses such as Ibrahim 34 at the beginning of this article give us clues about how to interpret scientific findings that reveal the amazing qualities of our bodily organs. May the Creator of our ears allow us to reflect more on His favors and live accordingly.

Hamdi Sener is a biophysicist living in Boston. He can be contacted at hamdisener@gmail.com.

References

1. Gleick, J., Genius: The Life and Science of Richard Feynman. Reprint ed. 1993: Vintage. 560.
2. Kemp, D.T., The evoked cochlear mechanical response and the auditory microstructure- evidence for a new element in cochlear mechanics. Scand Audiol Suppl., 1979. 9: p. 35–47.
3. Zheng, J., et al., Prestin is the motor protein of cochlear outer hair cells. Nature, 2000. 405(6783): p. 149–55.
4. Robles, L. and M.A. Ruggero, Mechanics of the mammalian cochlea. Physiol Rev., 2001. 81(3): p. 1305–52.
5. Gold, T., Hearing II. The physical basis of the action of the cochlea. Proc. Roy. Soc. B., 1948. 135: p. 492–498.
6. Rhode, W.S., Observations of the vibration of the basilar membrane in squirrel monkeys using the Mossbauer technique. J. Acoust. Soc. Am. , 1971. 49: p. 1218–1231.
7. Cho, A., What’s Shakin’ in the ear? Science, 2000. 288: p. 1954-1955.
8. Liberman, M.C., et al., Prestin is required for electromotility of the outer hair cell and for the cochlear amplifier. Nature, 2003. 419: p. 300-304.
9. Fettiplace, R. and C.M. Hackney, The sensory and motor roles of auditory hair cells. Nat Rev Neurosci., 2006. 7(1): p. 19-29.
10. Dallos, P. and B. Fakler, Prestin, a new type of motor protein. Nat Rev Mol Cell Biol, 2002. 3(2): p. 104-11.

Termites, one of the most common insects in the ecosystem, have very interesting specifications and social behaviors. These insects are of interest due to their ability to digest cellulose and to recycle organic foods found in rotten leaves, dead wood or wood chips. Although they are considered by some to be harmful to the economy-in the USA alone 600 million dollars every year-because they eat wood, in truth they bring about more benefit than harm. As a result of the activities of these insects, our forests are able to respire and regenerate. Termites break down old, decayed, and fallen trees, digesting them and thus helping nature to renew with a continuous circulation of vital substances. Despite the depth of information that is known about the ecological and economical importance of termites, only a little is known about their biological structure and behavior. Two characteristic features of these insects are that they live in social colonies and that they are very susceptible to infections, as they build their nests in soil or rotten wood. Since their environment is covered with damp and warm earth, they are also surrounded by an abundance of bacteria.

How termites arrange their social lives and how they protect themselves against illness are two main subjects being investigated by biological scientists. When termites encounter fatal fungal infections, the termites that first become aware of the disease start to send warning signals to the other members of the colony. Even at the cost of their lives, these members will continue to send warning signals. That is, for the health and prosperity of the whole society, some individuals of the group will sacrifice their own lives. One of these signals consists of the contractions and vibrations sent by the termite that caught the disease. One type of termite that makes its nest in wood starts to eat and destroy its nest when it catches an infection. The vibrations and sound of this activity are received by the other members of the colony, and they quickly realize that they are faced with an emergency situation. They then spring into action to move their nest to a more secure place. These communication experts exhibit different movements and behavior in order to inform others of different kinds of dangers. They use different methods to warn others about the existence of an intruder, or a hole in the nest, or a disease they have caught. Consequently, the vibrations and oscillations caused by the movements of the termites constitute a kind of Morse code for termites. In other words, termites talk to each other through these oscillations and vibrations, which to us appear as no more than a strange puzzle for us.

J. Traniello from Boston University investigated the communication systems termites use to inform each other about disease-making microorganisms as his research subject (Mechanisms of Disease Response in Termites) . He made a rectangular shaped Perspex (clear acrylic) nest which he has divided into two sections. The material used for the divisions allowed the termites to pass from side to side. Moreover, some tubes were also placed around the nest so that the termites could leave the nest. He placed termites in both of the sections. After an adaptation period, one part of the nest was infected by spores of a fatal fungus called Metahizium anisopliae, with the change in the behavior of the insects being observed and recorded. Termites that sensed the infected parts of the section started to move their bodies up and down and back and forth, as if they were breathing deeply and continued to depict seismic waves like oscillations and vibrations. Termites in the clean part of the nest felt these vibrations and within an hour had completely abandoned the nest. An interesting observation in the experiment was that the termites in the infected part stayed in the nest and continued to vibrate. In order to determine that the termites left the nest only after receiving the vibrations sent by the termites that had detected the infection, sound absorbent foams were placed between the sections, and the same experiment was carried out three times more. In the experiments conducted with the absorbent foam, despite the existence of the disease, the termites in the uninfected sections did not leave the nest. This proves that termites were receiving the vibrations from the infected termites and were replying to them by immediately deserting the nest.

It was thought that the termites in the infected area would also leave the nest after sending messages to the termites in the other section. This hypothesis, however, proved to be false. They stayed where they were and continued sending warning signals until they died. This was another example of the sacrifice observed in social insects that give up their own lives for the continuation of their society. The termite perceives the existence of a fatal bacteria attack and immediately starts to send warning signals; and by not abandoning their nest, they successfully put into effect a quarantine system. These social insects, without any intelligence, apply the quarantine system in such a precise manner that the disease is completely prevented from spreading. What is more, by sacrificing themselves for their society, they show that the principle of “if a person’s endeavor is for his nation, that person becomes a miniature nation on his own” is not only valid for human beings.

Ants, using a different method than termites, synthesize bacteria eliminating chemicals in their saliva glands that protect them from infectious diseases. These chemical combinations are very effective against bacteria and fungi. Ants protect themselves by covering their bodies with these substances at certain intervals. Termites, although in appearance not very different from ants, do not produce antiseptic substances in their bodies. Termites use a different strategy by establishing a symbiotic relationship with the bacteria that live in their intestines. Some termites that feed on decayed wood need enzymes to digest the cellulose. The cellulose needed by termites is synthesized by the bacteria in their intestines and turned into sugar. Thus, termites receive the glucose they need for survival and bacteria are provided with a comfortable berth in the bodies of the termites. Because of this symbiotic relationship, the production of fatal antibiotics that would kill the bacteria would be harmful to the termites themselves.

Instead of producing chemical compounds or antibiotics like ants, the seismic movements and self-sacrificing behavior depicted by the termites has given scientists the idea that it may be possible to benefit from termites as an early warning system for earthquakes. This idea is reflected in the Holy Qur’an, chapter Naml (The Ant), verse 18:

Until, when they reached a valley of ants, one of the ants said: “O you ants! Get into your dwellings lest Solomon and his army crush you unawares.”

This verse shows us the sensitivity of ants to vibrations. They have organs in their feet that are sensitive to movement. For one of those ants to have been able to warn the other ants, it must either have seen or sensed the coming of Prophet Solomon’s army. As obviously an ant cannot see an army coming from a long distance, they must have felt the vibrations made by the feet of the soldiers. We know that sound waves move very fast and are strong in solid objects. Because of this, by placing an ear onto railway track one can hear the vibrations of a train from far away. Termites most likely have an organ that receives vibrations that is similar to that of ants, because if a species can produce a signal (e.g. light, sound, or vibrations) for communication, they must also have an organ that is capable of receiving this signal. Since termites communicate with vibrations, they must also have an organ that is sensitive to weak vibrations. From this respect, if the code that is based upon some of the behaviors and vibrations used by the termites can be decoded, then are techniques of predicting earthquakes can be considerably improved.