Mew: The Embryonic Common Ancestor

Red/Green Mew
Red/Green Sprite
(February 1996)

Cats and mice aside, I think one of the most important influences on Mew's design is that of an embryo, and that the entire concept of Mew is based on the outdated scientific theory of recapitulation.

Cat Embryo
Cat Embryo

The similarity between Mew and an embryo is the most clear in the original Japanese Red/Green sprites, where Mew is shown hunched over, much like how an embryo is curled. Likewise, Mew's long tail might be intended to be reminiscent of the umbilical cord.

There also is a recurring association of Mew with bubbles and water, especially in the anime, which may be meant as references to the amniotic sac and the amniotic fluid that contain and protect a developing embryo. This analogy is driven even to the point of a seemingly dormant Mew being shown curled up and sleeping inside a bubble in The First Movie, before it wakes up and rises to the surface.

Mew asleep, curled in a bubble, underwater
Mew asleep in a bubble

There is also a Pokémon card featuring Mew in darkness with bubbles , and Pokémon: Lucario and the Mystery of Mew has a prominent scene where Mew is shown riding on the bubble-like structures of the Tree of Beginning . Mew also can summon soft pink bubbles at will , and Mew's psychic powers are often depicted as an orb of energy surrounding and protecting its small form at the center .

But why would Mew, the powerful and versatile ancestor Pokémon, have its design based upon an embryo, of all things?

Squirtle's evolutionary line, from the album art of the Game Boy Sound Collection original soundtrack
Squirtle's evolutionary line

I imagine that Game Freak was anticipating the players of the original Pokémon games, upon witnessing, say, Squirtle evolve into Wartortle and then again into Blastoise, to perhaps wonder, what was the form before Squirtle? And the form before that? And the form before that? If Blastoise is like an adult, Wartortle a teenager, and Squirtle a child... following this logic, the earliest form of all Pokémon would have to be an embryo. But there is even more to this design decision than that.

In the real world, as it turns out, all the many diverse vertebrate creatures tend to look similar during the pharyngula stage of embryonic development. In fact, this phase of development is sometimes called the phylotypic stage, because, while the developing embryos may look wildly different before this stage and may look wildly different after this stage, the pharyngula is a moment of solidarity for the entire phylum of Chordata. In fact, the definition of a chordate is to, at least at one point during the creature's existence, possess the features that all are present at this stage of development: a notochord, nerve cord, a tail, and pharyngeal slits. These traits distinguish chordates from creatures of other phyla.

Diagram of the anatomy of a lancelet, showing the notochord, the nerve cord, a post-anal tail, and pharyngeal slits
The anatomy of an adult lancelet, showing its retained notochord, nerve cord, tail, and pharyngeal slits

Some creatures keep these features until adulthood, such as lancelets, but many chordates only have them during development. For vertebrates, the notochord usually is eventually replaced by the vertebral column. As for the pharyngeal slits, in fish, they develop into gills; in humans, they mostly disappear, but also become the hollow parts of our heads associated with the ear (the auditory canal and the Eustachian tube).

Illustration comparing the pharyngulas of many species, including a salamander, a chicken, and a human
Controversial illustrations of embryonic development
Photograph of Ernst Haeckel with a skeleton
Ernst, I love your artwork, but you sure caused multiple setbacks for the popular understanding of evolution.

Recapitulation theory attempted to explain why such diverse creatures look so similar during the pharyngula stage, and why they all appear to have proto-gills. The idea was promoted by the German biologist and scientific illustrator Ernst Haeckel with the catchy phrase "ontogeny recapitulates phylogeny". In less dense words, this means that, as the embryo develops, it supposedly looks like its evolutionary ancestors before arriving at its current form. This theory implies that developing humans first appear similar to their single-celled protist ancestors, and then they appear similar to their early multi-cellular ancestors, and then appear similar to their fish-like ancestors (with pharyngeal slits), and so on, building upon each step and becoming more and more "advanced" until they reach their most-advanced modern forms.

Later scientists have found that this theory is completely wrong. This theory is based on the presumption that the natural world is an orderly hierarchy of lower and higher forms, with humans at the summit. There is also controversy surrounding Haeckel's illustrations of pharyngulas, claiming that he overly exaggerated the similarities to support his pet theory.

Despite the fact that recapitulation theory has long been discredited, I have witnessed not just lay people, but also science teachers and textbooks refer to it as truth, so it is an idea that has (unfortunately) had lasting impact on the popular understanding of evolution. However, factual science need not have any bearing on the Pokémon World. So, with this concept in mind, Game Freak seems to have based the design of the ancestor of all Pokémon on an embryo, because, according to this theory, the embryo reveals what a creature's distant ancestors once looked like.

The Developmental Hourglass
The so-called Developmental Hourglass, highlighting the pharyngula stage as both a re-convergence of form for vertebrates, and as a high point of global interactions for the embryo

While you're here, would you like to know what's up the pharyngula? Current thinking is that it is merely a conserved embryonic stage. As an embryo, the entire body plan of the developing creature is laid out. It is during this point of development that the most global interactions are occurring across the embryo. After this stage is done, the cells of each region will be more or less left to their own devices to develop into a particular organ or body part, and if anything goes wrong in the development of that part, this will most likely only cause problems locally. But during the pharyngula stage, an anomaly in the placement of the heart can have such far-reaching consequences as impacting the development of the eyes. As such, the pharyngula is the most vulnerable point of development; any deviation is sure to have drastic, and likely catastrophic, implications for the entire embryo.

Red using a computer
Bullet holes are not recommended for optimal computing performance

While Pokémon and lots of other media are rife with the trope of mutation as the catalyst for all kinds of superpowers, in reality, random mutations are usually not fun and games. I once had a biology teacher who described mutations as similar to trying to improve your computer by shooting it with a gun: there is a chance that you got amazingly lucky, and the resulting bullet hole somehow makes the computer work better (I don't know, maybe it missed all the important stuff and is providing better ventilation). But it is much more likely that now, your computer no longer turns on.

Because it is very unlikely that a mutation affecting this important and complicated developmental stage would be non-fatal, any organism with such a mutation is unlikely to be viable, let alone to live to the point of being able to pass on the mutation to any offspring. These forces against the lasting impacts of mutations to the pharyngula can be referred to as evolutionary pressure, and, as a result of this pressure, the pharyngula remains pretty much the same generation after generation -- this concept can be summed up by saying that the pharyngula stage is conserved. Lasting changes affecting this point of development are very uncommon, and, for them to be survivable, they tend to be gradual changes with little or no impact over many, many generations. This is why so many diverse creatures have similar-looking embryos, with the differences between them being relatively small. One species' embryo might flex a little bit more here, and another species' embryo might curl a little bit more there, but these minor changes do not disrupt the core similarities that remain conserved. In the end, while our embryo does not reveal what our common ancestor once looked like as an adult, our common ancestor's embryo presumably must have also looked similar.

In real life, an embryo is a developmental stage in a creature's lifecycle towards becoming an adult. When you talk about something being embryonic, you are talking about it being temporary, transient, and just beginning. An embryo, by definition, is not complete. However, life does not work this way for Pokémon. In Pokémon, each individual can remain in any stage potentially for its entire life. I said before that Squirtle is like a child, but there is no requirement that it must grow to become the "teenage" Wartortle or the "adult" Blastoise, and it is not in any way incomplete as a Squirtle. Each species of Pokémon is potentially a life stage, but also a fully-formed entity. So, with Mew, Mew is an embryo, but Mew is complete, while also containing potentially infinite beginnings.

On the next page, I will talk about the idea of Mew as a primordial creature with the potential to become and to learn anything.


  1. Japan-exclusive Pokémon Card from 1997
  2. Mew and Pikachu riding on the strange green bubbles flowing inside the Tree of Beginning
    Mew and Pikachu riding on the strange green bubbles inside the Tree of Beginning from Pokémon: Lucario and the Mystery of Mew
  3. Mew bouncing on a psychic pink bubble as if it were a giant cushion
    Mew bouncing on a psychic bubble in Mewtwo Strikes Back
  4. Mew's aura surrounds Mew as a pink sphere
    Mew's psychic powers often take the form of a pink, sphere-like aura surrounding its form.