During our university days my geneticist friends and I would often unwind from intense bouts of lectures, experiments and report writing by attempting to answer profound, videogame-related questions. Could the human genome accept foreign genetic material like Rapture’s plasmids? Could a man’s excellence in combat be identified genetically and duplicated as performed in Metal Gear Solid‘s Les Enfants Terribles experiments? And could a fox be born with two fully functional tails?

When he first appeared, Tails did seemingly little to stand out from the myriad anthropomorphic animal characters that dominated children’s entertainment in the early 90’s.

When he first appeared in Sonic the Hedgehog 2, Tails did seemingly little to stand out from the myriad anthropomorphic animal characters that dominated children’s entertainment in the early 90’s. Players soon realized, however, that it wasn’t so much his twin tails that defined him, but rather the novel way he used them. By rapidly rotating his tails, the little orange fox could propel himself across land at high speeds as well as fly through the air, helicopter style.

Tails’ peculiar trait was a response by Sega game designer and artist Yasushi Yamaguchi to an in-house competition to create a sidekick to star alongside the blue blur in the follow-up to Sonic the Hedgehog. Aside from the name, which was changed from “Miles Prower,” a pun based off “miles per hour,” to “Miles ‘Tails’ Prower,” the in-game appearance of Yamaguchi’s winning entry remained relatively unaltered and Tails has been a prominent character in the Sonic franchise ever since.

It’s likely that Yamaguchi’s design of a red fox with two tails drew from the many ancient Japanese mythologies surrounding the red fox, or “kitsune,” which persist in Japanese culture to this day.

Although the details vary from story to story, kitsune are generally described as intelligent spirits capable of various amazing feats including possession, shape shifting, emitting fire and lightening, and reaching incredibly old ages. In fact, after every 100th birthday, kitsune will grow an additional tail and gain a boost to their wisdom and magic up until the ninth tail, at which point their fur turns gold or white and omnipresence is bestowed upon them.

Some folk tales also describe a kitsune’s 100th birthday, the day it grows its first extra tail, as the same day it is granted the ability to shape shift into humans. Tails’ extra tail and anthropomorphic appearance may very well be Yamaguchi’s modern rendition of a 100 year old kitsune. But if he was inspired by kitsune myths, what inspired the mythmakers?

Similar tales of multi-tailed foxes were told across ancient China and Korea and, due to being the most geographically widespread carnivore on Earth, red foxes and their multiple sub-species appear in some form or another in the folklore of almost every known civilization. Is it possible, then, that at some point in human history someone has laid eyes on a red fox with two fully functional tails and if so, what developmental mishap would have resulted in such an astounding outcome?

In order to answer that question we must first look at the very basis of developmental biology, the scientific discipline concerning the development, growth and maintenance of organisms.

Almost all multi-cellular organisms, be they plant, fungus, fish, insect or anything else, are derived from an egg that has been fertilized by a sperm resulting in an embryo containing an entirely new configuration of DNA. From this new, single-celled entity individual cell types must arise, different tissues and organs must grow, and an entire organism must be formed.

In animals this is achieved through an intricate choreography of cell divisions, cell-to-cell communication, timed gene expression and chemical concentration gradients. But where amongst such a high volume of interlinked events does the answer to our question lie? If our friend Tails the red fox, a mammal, truly wished to enter the real world, then a good place to start would be the coincidentally named protein “sonic hedgehog homolog.”

The story goes as follows: During the early 1980’s a gene responsible for the correct patterning of the insect body plan was identified through a mutant fruit fly whose unusually stubby maggot offspring had bristles covering their bodies in places they would not normally grow, and thus the gene was named hedgehog. The homologous gene (i.e. gene derived from a common ancestor) in mammals and birds was discovered by a postgraduate student in 1993 who officially named it sonic hedgehog, because geneticists are gamers too (read: pokemon gene).

Given the incredible level of similarity of both embryonic developmental genes and processes between mammals, it is highly probable that the same developmental outcome could be achieved with a red fox.

Sonic hedgehog the gene codes for sonic hedgehog the protein, which is itself part of a complex series of chemical interactions involved in the embryonic development of key organs and tissues including the nervous system, spine, hands, feet, the forebrain, heart, lungs and many more. This “hedgehog” signaling pathway is present in all animals with bilateral symmetry – i.e. a top and bottom, and a front and back. Of interest to our hypothetical Tails, however, is sonic hedgehog’s role in regulating the width of the mammalian face.

Embryos deficient in sonic hedgehog in what will become their face have deformed or absent ears, one single brain hemisphere and a single, gaping hole where the eyes and nose should have been; a range of fatal birth defects known as cyclopia. Conversely, a higher than normal concentration of sonic hedgehog will result in wide set eyes and broad noses while extremely high levels yield the most striking deformity of all; the front of the face splitting off into two, a disorder known as craniofacial duplication [1].

Cases of craniofacial duplication have been reported in cats, pigs and even humans. But of what interest would two faces be to a fox wanting two tails? As previously mentioned, the basis of embryonic development is conserved throughout all mammals. It stands to reason that if the complex organs found in a mammal’s head can be duplicated via increased levels of embryonic sonic hedgehog, then the same or a similarly functioning protein may achieve the same result if increased at the precursor of a fox embryo’s tail.

Such a phenomenon does not appear often in the scientific literature but has indeed occurred spontaneously in lab mice. A paper published in 1975 described a single mouse of a mutant strain with bent tails which had one normal and one deformed tail.

Nearly 40 years earlier it had been observed that roughly 10 percent of mice of a strain known as “Fused,” which suffered from numerous deformities including missing or fused ribs and fused vertebrae, were born with an extra, smaller tail splitting off from the “main” tail. While the smaller tails were never longer than 3cm, they did contain the skeletal structure and nerves necessary, albeit deformed, for movement. Later studies showed that the gene whose mutations cause the “Fused” effect, named Axin, regulates a very early step in determining an embryo’s axis in both mammals and amphibians.

Given the incredible level of similarity of both embryonic developmental genes and processes between mammals, it is highly probable that if the cause of the twin-tailed mice could be pinpointed and duplicated, the same developmental outcome could be achieved with a red fox or any other mammal.

Unfortunately for foxy Tails wannabes it is extremely unlikely that this has or ever will occur in the wild. The astronomical amount of lab rats of various strains bred by man over the years dwarfs that of the world’s population of red foxes, and considering the harsh environments foxes are born into and the tendency for unhealthy cubs to be abandoned by parents, any genetic mutation that may give rise to a two-tailed fox would be swiftly eradicated by natural selection. While the natural birth of a living two-tailed fox is almost certainly possible, the probability of it having a non-fatal combination of developmental defects, and then surviving its birth, upbringing and adult life, is close to zero.

Those looking to the luxurious conditions of the test lab for a real-life Tails will also be disappointed. One of the main driving forces behind developmental biology is the fact that discoveries made with one species of mammal are likely to hold true for humans. Therefore insights into human ailments and potential treatments can be gained without invasive and unethical human experimentation. Simply put, there’s little to no scientific value or gain to humanity in attempting to engineer a fox with two tails.

But so what if Yamaguchi’s inspiration for Tails was originally derived from the vivid imaginations of a few ancient Japanese storytellers? It’s fun to imagine. After all, with good imagination comes good questions, and with the best questions come the best answers. Now where did I put that vial of Adam …

Michael Westgarth is a freelance writer and geneticist for hire. Discover more of his work on his blog MegaWestgarth and pick his brains through Twitter @MegaWestgarth.

[1] Information sourced from Mutants: On Genetic Variety and the Human Body by Armand Marie Leroi, 2005, Harper Perennial.

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