Monsters go in and out of fashion. Vampires had their moment a few years ago, only for zombies to eat their lunch (and brains) once the walking dead became the monster du jour. Now it seems as though werewolves might be getting their moment in the sun — or, rather, in the moonlight.
Examples of werewolves on film predate the 1941 film The Wolf Man from Universal Studios, but none so successfully captured the public imagination. The film, starring Lon Chaney Jr. as the titular character, was successful enough to garner several sequels and a reboot in 2010. Decades later, in the '80s, werewolves enjoyed a surge in popularity with such films as An American Werewolf in London and Teen Wolf, starring John Landis and Michael J. Fox, respectively. For a while afterward, popularity ebbed again until the early 2000s, with the emergence of the Underworld franchise.
Much like the lunar cycle itself, the popularity of werewolves seems to spike but for a brief moment, only to subside again. Now, with the second seasons of The Order and What We Do in the Shadows, the moon is rising once again.
Perhaps the easiest way to trace the journey of on-screen werewolf narratives is by reviewing the evolution of transformation sequences. In earlier appearances, the transformation from human to monster often happened offscreen, or else was minor in appearance. As special effects technologies have advanced, however, the transformation has taken center stage, involving drawn-out and often painful transitions beneath the moonlight.
Unlike vampires or zombies, werewolves require a drastic change in body structure in order to become their true, monstrous selves. Bones become longer, claws erupt, and skin stretches. The pupils change shape, in order that the werewolf might better see in the dark. While most creatures of the night maintain their basic physical structures, more or less, werewolves must undergo drastic fundamental physical changes, and not just once, but many times. It has us wondering — are there any real-world examples of such extreme changes as lycanthropy induces? Are caterpillars just werebutterflies?
CHANGING BODY STRUCTURE
There are countless examples, in the animal kingdom, of creatures that undergo considerable metamorphosis, changing so drastically as to be almost unrecognizable. Perhaps the most common example of this is moths and butterflies. The change from a caterpillar to a butterfly is so drastic, in fact, that some scientists previously believed them to be separate species entirely.
Without the benefit of modern knowledge, you could be forgiven for believing caterpillars and butterflies were different animals. They share very little in common, in terms of both behavior and physical structure. Unlike many vertebrate animals, like reptiles or mammals, it's difficult to see how one stage of the life cycle progresses to another.
The basic body plan of any species is primarily defined by Hox genes. These genes are responsible for the basic blueprint of the body — think of them as being responsible for the basic sketch of your body, before the other genes come in and fill in the details. In short, they are responsible for saying: "Head goes here. Limbs go here." That sort of thing.
Each of us has a unique genetic structure, responsible for all the minute details that make us individuals, but our Hox genes are the same. In fact, they are largely the same even among different species, so long as the basic body plan is similar.
In humans, our Hox genes determine our basic structures, and any massive change in those structures would require a change in those basic instructions.
A shift, for instance, from a human body plan to that of a wolf would necessitate quite a lot of rearranging on the genetic level. Humans and dogs last shared a common ancestor roughly 100 million years ago. That's a whole lot of tape to rewind in order to go feral when the full moon rises.
How, then, do animals like caterpillars make such incredible changes from one stage of life to the next?
The answer lies in those very same Hox genes.
You might suspect that, in order to undergo such a transformation, an animal would have to have two sets of these blueprint genes, but that isn't the case. One set of Hox genes can be responsible for both divergent body plans; it's all in how those genes are expressed down the line.
It turns out, the body plan of a caterpillar and a butterfly aren't all that different. Both share similar structures, laterally, from head to tail (so to speak), at least in terms of how the basic structures are laid out. The major differences lie in what is done with those structures once they're in place.
A notable example of this sort of expression comes from a bizarre experiment, in which the Hox genes of a fly were replaced with those of a chicken. In at least some cases, this resulted in flies that looked, by all appearances, like flies. This, despite the fact that flies and chickens diverged on the evolutionary tree some 550 million years ago.
This suggests that while Hox genes play a vital role in the structuring of our bodies, other parts of our DNA do a lot of the heavy lifting when it comes to the end result. So it is with caterpillars and their transformation into butterflies. So it must be, if we want to transform a human into a humanoid wolf. We likely wouldn't need a new set of Hox genes in order to become a wolf, but we would need to change the way those genes are expressed down the line. And caterpillars might give us a clue about how to do that.
In caterpillars, certain clusters of cells known as imaginal discs hold the instructions for what it will become later in life.
After a series of molts, when a caterpillar becomes ready to initiate its final transformation, it encloses itself in a cocoon or chrysalis. Once inside, it releases enzymes that very literally digest its body, turning it into caterpillar soup in a handy to-go container.
Importantly, not everything is digested. Those imaginal discs survive the ordeal, and use the soup to develop into the final form. It's almost as if the caterpillar reverts into a second gestational period, behaving like a new embryo, beginning the developmental process once again in order to emerge as something else entirely.
Those imaginal discs exist inside the caterpillar, holding all of the genetic information required to become a butterfly, but are dormant. What changes is not the genetic information available in the body of a caterpillar, but, instead, the expression of those genes.
There are, of course, other animals that undergo a metamorphosis without the complete destruction of their previous selves. Tadpoles change into frogs, a process that completely changes their body structure, including limbs and organs, but the change is less drastic.
A metamorphosis of the kind butterflies undergo seems to require a more severe approach. It's reasonable to assume human to wolf transformation would require a similar process. Perhaps the next generation of monster movies will take this into account, introducing the world to a generation of werewolves in which a bite from the cursed creatures introduces imaginal discs into a host, at which point the unassuming human, under pressure from the lunar cycle, will enter a coarse-haired chrysalis, dissolve into some disgusting soup, and emerge in its true, hideous form.
One can dream.