The answer is apparently 'yes'.
Before I became lost in a whale's stomach, I was exploring the second special exhibit at the Ontario Science Museum on mythical creatures. (Any objections to the location of such a display should have been made when I described the Harry Potter themed production at said same science-focussed location). The question raised --whether a creature that only existed in people's imaginations could die-- was answered with the example of the Nasca killer whale. Heard of it? Well no, that's pretty much the point. Once though, it appeared to have been a legendary monster.
The Nasca lived in south Peru from around 1 - 700 AD. Many archaeological finds from that period depict a killer whale holding a human head. All stories centred around such a beast, however, have been lost. Indeed, from what is known about the people from that time, it is not possible to even ascertain if the creature was good or evil. Personally, I would have thought that holding a severed head intimated one of those two options, but apparently head collecting was the thing to do at the time and he might just have been trying to fit in.
Not only can these creatures die, but they are also victims of evolution. Unicorns, for instance, used to have the body of a goat with a short coloured horn and griffins did not always have wings. Likewise, there is the Canadian Inuit legend of Sedna (a human, not a planetoid) which describes how a girl rather rashly decides to marry a bird, unsurprisingly regrets it, and is rescued by her father. In a feathered fury, the jilted bird conjures up a storm and the father decides to cut his losses and throw Sedna overboard. Unwilling to comply, Sedna clings to the boat, forcing her father to cut off first her fingers and then the knuckles. The first of these become the whales of the ocean and the second the seals. Continuing to demonstrate an unhealthy tenacity, Sedna survives to persuade a dog to chew off her father's hands and feet. He curses them all which causes the earth to open and swallow them both into the underworld. While originally all human, mermaid images introduced by merchants and slaves later became became associated with Sedna. Such travellers' tales explain why legends that originated thousands of miles apart often share common features. Mermaids, apparently, always have a penchant for combs and mirrors.
The original origin of each mythical creature could stem from different courses. Largely, it seemed that their creation was the product of four distinct situations:
The first of these was that of mistaken identity, especially of decaying remains. One such example was a sea monster that turned out to be the carcass of a 9m basking shark. Likewise, in 1855, the Danish Zoologist, Japetus Steenstrup, proposed that the fabled sea bishop observed in the 16th century was actually a large squid. Of course, since the Giant Squid can be up to 18m in size and there is an even larger Colossal Squid with eyes as large as a human head, the classification of 'monster' becomes a bit of a mute point. Amusingly, in 1300, Marco Polo described seeing unicorns that were probably Sumatran Rhinos. Suffice to say, he was unimpressed by their beauty. A giraffe was later mistaken for a unicorn when it was presented to the Chinese Emperor in 1414 by the explorer, Cheng Ho. Possibly due to accounts of this tale, the Japanese word for giraffe, Kirin (麒麟), also means unicorn.
The second origin was fear. The open ocean, with its seemingly infinite extent in all directions including down, can seem to hold any number of horrors. In such a place, the arched backs of jumping dolphins could easily appear to be the many tentacles of a kraken. Matters were perhaps not helped by Konrad Lykosthenes, who published an encyclopedia in 1557 detailing the monsters awaiting sailors. Similarly, Conrad Gesner's 1563 zoological work included a hippocampus; a sea creature with a horse's head, reinforcing the theory of the time that every animal found on land had a counterpart in the ocean.
Many mythical creatures were created to explain mysterious phenomenon. For example, Mexican farm animals were sometimes found dead with open gashes. Such events were blamed on 'Chupacabra'; small blood sucking creatures with glowing red eyes who kill like vampires of the non-sparkly ilk. Modern medicine has since revealed that gas in a carcass can cause it to expand and form splits of seemingly surgical precision. Giant bones from extinct creatures, such as those from dinosaurs and the huge ape gigantopithecus blacki, were also frequently thought to only be explainable by mythical beasts. Even elephant skulls, understood when alive, could resemble the remains of a Cyclops in death, with the opening in the skull for the trunk the space for its single eye. The fact these creatures are associated with forges, incidentally, came from the ancient Greek blacksmiths, who wore an eye patch to protect their sight from flying sparks. The Greek mythology, meanwhile, explained the natural disasters of earthquakes and volcanoes as originating from the torment of the giant children of the gods Uranus and Gaia, trapped by Zeus after the battle of Gigantomachy.
Finally, there were mythical creatures whose existence was through a story with a moral. One such creature is the goblin-like, Japanese tengu, who live in the forests to mock and punish prideful people. Their legend tells of a man walking through a forest and finding a tengu who agrees to teach him the magical art of ninjutsu. Rather than use his new skills for worthwhile causes, the man kills and steals from travellers. In one unfortunate evil act too many, he tries to kill a slow farmer who was in his way. Rather than slay the poor man, his sword breaks, revealing said farmer to be the tengu and himself unable to use his powers again. The Japanese saying "tengu ni neru" (he is turning into a tengu) is commonly used to recall this tale and warn people against arrogance. In 1860, the Japanese government posted official notices to tengu asking them to temporarily vacate a certain mountain during a schedule visit by the shogun. I cannot help but feel this revealed a particularly honest view of the characters of the country's commanders.
Sometimes the origin of a creature cannot be even guessed at due to the age of its legend. Griffin illustrations are found that date back to 3300 BC. The Greek myths are known to be at least 2,700 years old, but their material is borrowed from still more ancient tales.
A few modern mythical beasts are created through more mundane means. In 1842, the people of New York City were enthralled by the shrivelled corpse of the 'feejee mermaid' . The creature was shown by P. T. Barnum who acquired it from a colleague in Boston. In reality, the little body was made by fusing the torso of a monkey with the tail of a fish. Such fakes were made in the East Indies and sold to British and American sailors in, what one can only suppose, was an early tourist trade. Ideally, one would like to think we are now above such mockery, yet pictures on the internet of mermaids washed up on shore after a tsunami beg to differ.
For some, the creation of phoney creatures is not so much trickery as an art form. Bob Slaughter had a distinguished career in palaeontology before moving into the business of making attractive fake fossils of small winged humans and their friends. His book on this appears to have fooled at least one amazon.com reviewer. There is also the Coney Island artist, Takeshi Yamada, who creates 'gaffs' including a taxidermied rabbit with a fish tail.
Aspects from mythical beasts have also wound their way into modern associations. The pokemon character 'aipom' resemble the ahuizotl; a monkey creature with an unfortunate pastime of pulling people underwater and drowning them. 500 years ago, the same creature was carved into the wall of an Aztec temple as pictographic symbol of the ambitious Aztec leader who took its name. A similar creation with a taste for drowning is the Japanese kappa. When it's not disguising itself as a child in preparation for watery demises, the kappa apparently likes cucumbers, resulting in the sushi cucumber roll to be known as 'kappamaki'. It is also the origin of the phrase 'even kappas can drown', referring to the fact that even experts can make mistakes, and 'just a kappa fart' which a cruder form of 'a much ado about nothing'. Amusingly, the kappa is very much the product of the culture it was born in. Their strength originates from water in the bowl shaped dent in their head. To defeat the creature, you bow to it, whereupon manners will force it to bow in return, spilling the water and causing it to flee back to the river or pond.
Not all questions about mythical creatures were answered by this exhibit. As I stood in front of a model of the flying horse, Pegasus, child of Greek god Poseidon and monster Medusa, a teenager beside me turned to her friend and demanded, "How can two gods make a horse?"