The Biological Feasibility of the Children’s Television Program Naruto: A Case Study

William YuanFrank Wang

Introduction

Naruto is an ongoing anime series produced by TV Tokyo and Viz Media inspired by the Japanese manga series by Masashi Kishimoto. It follows the exploits of the titular character, Naruto Uzumaki, in his quest to become the most powerful ninja in his village and battling various evil entities and organizations. The series is wildly popular, reaching millions of children and teens around the world. Given this widespread permeation, its effects on the perceptions of science, especially biology are questionable. Unlike many shows in its genre, Naruto is one of few that not only acknowledges, but discusses biology. With talk of symbiosis, genetic bloodline traits, prosthetics, and medicine, Naruto has the potential to reach an enormous population and introduce them to science in an unexpected environement. Thus, this study seeks not only to study biological and physiological feasibility of various aspects and characters of the show and attempt to explain them in a biologically accurate manner, but also investigate the dichotomy between actual reality and public perception thereof. Along with their explanation, plot devices and characters will be ranked on the following scale of potential accuracy:

A: Likely possible in the real world, within realm of possibilityB: Requires the creation of several invented concepts, technically possibleC: Requires creation of many invented concepts, theoretically possibleF: Not possible under current understanding of biology/technology Characters in the series use a mystical energy referred to as “chakra” to perform various superhuman techniques. For the sake of explanation, this energy will be assumed not to interfere with basic scientific concepts, but can perform tasks that exist within the realm of possibility. With this in mind, four concepts have been selected and described below.

Sharingan (Enhanced visual acuity, copying physical actions)

Premise

Several characters in the series possess the Sharingan, a technique which, upon acativation, turns the user’s eyes red with several large dots and increases visual acuity, reflexes, and allows the user to copy motions or techniques used by

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enemies. Jumps, acrobatic flips, and complex hand signs used to cause various phenomena can all be copied as they happen, and then used. The user can then revert their eyes to their normal condition.

Figure 1: The Sharingan Eye

Proposed Explanation

In order to increase the ocular abilities mentioned, the number of cones will need to be increased. Cones are photoreceptors in the retina that are able to respond and adapt much more quickly than their counterparts, rods, and are also responsible for visual acuity and high resolution vision. However, cones are generally only located in the fovea, or the center of the visual field. Therefore, the extra three dots are not simply cosmetic, but are extra pupils. More pupils would increase the number of fovea to four, and allow the user to focus on multiple points of reference and thus increase general optical performance during conflict.

Increasing reflex speed is as simple as increasing the myelination of the optic nerve and motor neurons, allowing faster signal transmission, which would also allow the copying in question. Upon visual stimulus of a particular action, a reflex, copying that action could be triggered, further increasing the speed by cutting out interpretation of the central nervous system to the speeds depicted in the show. Finally, increasing the physical size of the cerebellum and basal ganglia would potentially allow acceleration of motor learning.

Red irises are merely symptoms of ocular albinism.

Survey Data:

A: 8.7%B: 13%C: 47.8%F: 30.4%

Figure 2: Sharingan Survey Data

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Grade: B

While theory behind the Sharingan Eye is technically sound, having multiple pupils is called polycoria (see Figure 3), and is a disease (generally a pathological defect of the iris), rather than a desirable trait. Additionally, there is no way to “turn off” the various physiological enhancements mentioned. Anyone using this technique would be stuck with it permanently.

Figure 1: Examples of Polycoria

Kakuzu (Multiple Hearts) Premise

A later antagonist in the series is a ninja named Kakuzu, who has augmented his body with multiple hearts, giving him a form of immortality in that he could not die until all of his hearts are destroyed. Although this is not explored in the show, it will be assumed that Kakuzu will not die from lack of circulation until all of his hearts fail, and can die from other unrelated processes.

Figure 5: Simplistic Parallel Circulatory System

Figure 4: Kakuzu’s Hearts (enclosed in masks)

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Proposed Explanation

There are several explanations for this structure.

If a human possessed 5 hearts in series, if one in line were damaged, the entire system would fail, something not observed in the show. Therefore, some sort of redundancy must exist in his circulatory system. Similar to how the lymphatic and circulatory systems are closely intertwined in humans, Kakuzu likely possesses either multiple sets of atria, capillaries, and veins wound around each other(see Figure 5) or has his hearts arranged in parallel (see Figure 6). Therefore, should one heart fail for some reason, after cauterization to prevent shock, blood could still travel through the body by either entering a separate circulatory system or heart. Redundancies in his cardiovascular system could account for the supposed immortality that he possesses.

Another possible explanation is that Kazuku is actually a separate species. For example, Kakuzu could be a species of highly complex earthworm, which possess five hearts around the esophagus along with a main dorsal blood vessel. Alternately, he could be a member of the class Cephalopoda, members who possess multiple hearts: two brachial hearts along with a systemic heart. They are also the most intelligent invertebrates, with well developed senses, large brains, and complex nervous systems. Human level intelligence is not completely far out.

Grade: C (redundant circulatory system), F (separate species)

While Kakuzu’s thoracic cavity is large enough to contain redundant circulatory systems (he stands 6.07 ft tall), he does not weigh enough (~140 lbs) for one to realistically exist. A parallel circulatory system has never been observed, though would presumably work similar to a parallel electrical circuit. Kakuzu is observed to possess a backbone, ruling out the possibility of being a cephalopod, and does not fit the body plan of an earthworm.

Figure 6: Multi-set Circulatory System, Numbers refer to independent Circulatory Systems

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Survey Data

Byakugan (360 degree field of view, individual signature identification)

Figure 8: Byakugan Eyes

Premise

“Byakugan” is the name of the ability, which, like the Sharingan, grants the user enhanced visual and ocular powers. While it is activated, the user can see over a 360 degree field of view, similar to having eyes on the back of one’s head. Additionally, when in situations where one cannot see clearly, the Byakugan allows the user to identify individuals based on a specific electrochemical signature, giving them an edge in combat. While activated, blood vessels around the user’s eye swell prominently. The eyes, when not in use, are completely white.

Proposed Explanation

The spacial structure of the face does not allow the eyes to see wider than a certain field of view. Some species, such as birds, have eyes located further apart, near the sides of their heads, allowing for different ranges of vision, although not necessarily exceeding a certain capacity. Human eyes exhibit

A: 4.3%B: 21.7%C: 39.1%F: 34.8%

Figure 7: Kakuzu Survey Data

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considerable overlap, and assuming there is no overlap, 360 degrees is still grossly unachievable.

The ability to detect and sense others when visibility is poor must originate from a combination of senses. The first is echolocation, or location by hearing. Bats and dolphins use echolocation to locate food, predators, or even to navigate. Emission of ultrasonic waves and analysis of their reflection patterns could produce a 360 mental map. However, echolocation cannot distinguish biotic factors, which may be a threat, from abiotic ones, which are not. Therefore, infrared radiation detection, as evidenced in rattlesnakes, is likely used in conjunction. Heat signatures emitted by others could be detected, and provide a degree of conformation to the echolocation map, providing a makeshift form of echolocation.

Infrared vision is unlikely to allow users to distinguish individuals apart. Therefore, a highly attuned sense of smell, such as in bloodhounds of pigs could be used to identify unique chemical tracers to allow for positive identification.

Generally, white eyes are associated with blindness, and the extra senses described do not generally have a place in the human brain. Therefore, it is likely that the occipital lobe of the brain is replaced with additional auditory, infrared, and olfactory processing centers. Instead of actual “eyes,” the eyes of a Byakugan user would simply serve as a repository for the sensors described.

Survey Data

Grade: F

The senses described have never been observed together in any organism, and have rarely, if ever, been observed individually in humans. For individuals to somehow accumulate all three traits would be a miraculous happening.

C: 26.1%F: 73.9%

Figure 9: Byakugan Survey Data

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Additionally, the solution described would prevent users from reading or writing, something which they have been observed to do.

Finally, blood vessels swell in the users face when the Byakugan is used, but in the human face, there are no blood vessels to swell (see Figure 10). Blood vessels from the eye tend to travel on the opposite side of the eye.

These impossibilities together make the possibility of such an ability very remote.

Figure 10: Blood Vessels of the Human Face, Byakugan for comparison. Observe the lack

of vessels near the outer sides of the eye.

Endosymbiosis with Insects

Figure 11: A Member of the Aburame Clan with his Insects

Premise

In the show, the Aburame Clan is depicted to possess a special endosymbiotic relationship with a species of insects. The human host provides shelter and energy in return, is able to command the insects as weapons. These insects live under the skin in hives of thousands of individuals.

Proposed Explanation

This is a type of mutualistic symbiosis. The insects live within the human, while

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acting as both defensive and offensive mechanisms. The symbiosis is a lifelong relationship, as both parties protect each other to ensure mutual survivability. The human body acts as a home and a host of nutrients for a swarm of insects, who likely feed off excess nutrients, fat, or even wastes (for example, the CO2 emitted through respiration).

Figure 12: Symbiotic Insects used by the Aburame

Because the insects live inside the body, a harmless nesting area in or near one of the body cavities would need to exist. Similar to the e. coli in the intestines, these insects could serve beneficial purposes in the digestive tract. Travel through the skin likely occurs through ducts lined with mucous membranes or other immune guard-like cells to prevent a conduit for potential infection.

Survey Data:

Grade: C

The primary concern with this type of symbiosis is preventing an internal immune response. The mere presence of foreign organisms of that size inside the human body could trigger allergy-like effects, inflammation, or cysts, as in the case of parasitic worms, all of concern to a potential user of these insects.

B: 21.7%C: 34.8%F: 43.5%

Figure 13: Endosymbiosis Survey Data

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Additionally, the thoratic cavity, the most likely home of these insects, is hardly an empty space. It is filled with interstitial fluid, organs, etc, hardly a habitable environment. The sheer volume of thousands of insects could potentially cause trauma to internal organs due to their mere presence. It is stated that these insects in particular have a lifespan of only a few hours, meaning more space for reproducing insects and insect corpses would be needed. Insects living inside would also be forced to find a way to either tap into the trachea or lungs or use dissolved blood oxygen in order to carry out respiration.

Finally, in terms of size, are relatively large (see Figure 11). In order to travel through the skin, relatively large openings would be needed. Additionally, potential infections caused by insects traveling from inside out and back would cause further strain to the immune system.

Endosymbiosis in humans can work, but the size and function of these insects makes it difficult to imagine.

Conclusion

Overall Grade: C

While some concepts used are theoretically sound, far too many technical limitations exist for events to occur realistically as depicted.

While Naruto possesses many innovative ideas and could be considered a source of inspiration for future medical, biological, or physiological techniques, many concepts presented in the show are simply unfeasible biologically or technologically. Additionally, biological oversights such as the weight of multiple cardiovascular systems or swelling of blood vessels that do not exist are serious and simply cannot be overlooked. Viewers of the show surveyed tended to either dismiss or look skeptically upon the pieces of the show studied. This trend continued, even if a trait was found to be plausible or even possible. This skepticism can be helpful, but is also rather troubling given the potential some of the ideas presented have. Given the show’s massive popularity, producers and writers of Naruto should strive to produce more biologically and physiologically accurate content, while maintaining the conceptual innovation which has rendered their show a success.

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Appendix: Cut Content

Accelerated Healing

Premise

The titular character of the series, Naruto Uzumaki, possesses the ability to recover from various wounds extremely quickly, ranging from basic cuts and bruises to massive amounts of internal organ damage. This ability comes at the supposed cost of shortening his overall lifespan.

Figure 24: Instantaneous scratch recovery

Proposed Explanation

Upon an injury, increased anchorage dependence in Naruto’s cells trigger cyclins and cyclin-dependent kinases in his body to rapidly accelerate the cell cycle. Additionally, growth factors are used to stimulate cell division. This allows his body to regrow tissues that have been damaged extremely rapidly. In real life, platelets at an injury site release a growth factor called PGDF stimulating fibroblast proliferation and eventual healing. Alternately, combinations of oncogenes and p53 genes could accelerate the cell cycle, and with it, healing, while providing protection against uncontrolled cell growth and cancer. Oncogenes would affect proteins to either accelerate the cell cycle or remove inhibitors to accelerate cell growth, while p53 genes repair any extraneous damage.

The “cost” of shortened lifespan also possesses and explanation. Because requires a 3’ end to add nucleotides, the RNA primer on the 5’ end cannot be replaced. Generally, cells possess telomeres, caps on the end of DNA which postpones the damage caused by cell division. However, given the acceleration of mitosis which is used to accelerate healing, genetic damage resulting in defective protein construction and potentially cancer would inevitably trigger an earlier death.

Survey Data:

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Grade: A (Cyclins/CDKs), C (Genetic Control)

Using cell growth as a form of accelerated healing could work, and is merely an acceleration of an existing biological process. A realistic drawback to the ability is also present. Usage of oncogenes and p53 genes antagonistically could be possible, but likely lacks the fine control needed for the precise healing depicted.

Zaku (Stomas through Arms/Forcibly Expel Air through Hands)

Premise

Zaku is a physically altered character with the ability to control air pressure using his limbs. He was implanted with hollow tubes in both his arms that open through his hands. There are no visible canisters attached to his body, so it is assumed that the source of the air comes from his respiratory system.

Figure 16: Zaku Shooting Air out of his Hands

Proposed Explanation

His implanted hollow arm tubes are likely attached to his trachea and the bronchi of his lungs. Together, they would form an intersection, with the both arm tubes sticking out of the left and right sides of the trachea right above when it connects to the bronchi. The hollow tubes run unimpeded through his arms as his movement is neither constricted nor robot-like. The tubes are likely narrow and flexible, ultimately leading to the opening in his palms. The ending of the tube

A: 34.8%B: 21.7%C: 30.4%F: 13%

Figure 15: Healing Survey Data

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could simply be curved up to accommodate the fact that the center of the palm is not directly in line with the forearm. Similar to how we control our breathing, he controls expulsion of air in any magnitude he can attain through pressure exerted by his lungs and diaphragm.

Because the air he releases is depicted to be at a greater velocity than when normal humans exhale, it means additional pressure is added somewhere during the process. Because his arm tubes were implanted, the tubes could have come with a smooth muscle graft. The smooth muscle lining the tubes propagate their contractions, resulting in a peristalsis-like effect similar to the one in our alimentary canal, providing additional pressure and velocity for expelled air.

However, these tubes cannot be the only source of exhalation. In the show, Zaku’s arms are broken at one point, which would have caused death if those were his only means of respiration. Therefore, he can consciously control whether he breathes through his mouth, nose, or hands, similar to how we can decide to breathe through our noses, a factor which is confirmed by his conscious control over use of this ability.

Survey Data

Grade: BImplanted tubes into the junction of the trachea and bronchi are not unheard of. Cigarette smokers can and do end up with stomas surgically inserted into their necks. These stomas work functionally the same way that Zaku’s arm tubes do. A major point of concern manifests itself as physically having the arms physically function with hollow tubes inserted inside them. Medically suitable tubing could be acquired, though no matter how flexible it is, there is bound to be some awkwardness in movement. Finally, the co-existence of both smooth and skeletal muscle in the arm would result in a much more complicated nervous system control in the limbs. Overall, all these changes could be possible only with advanced medical technology, something a society of ninjas is unlikely to have.

A: 13%B: 34.8%C: 26.1%F: 26.1%

Figure 17: Zaku Survey Data

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