On the Origin of Species: Mew
When I first played Pokémon Yellow at the tender age of nineteen, there was still an air of genuine mystery and excitement surrounding Mew, the very first event-exclusive Pokémon. There was no global trading or Wi-Fi distribution back then: if you wanted Mew in your Pokédex, you had to be damn lucky.
Or you could cheat, I suppose, but that's not the point.
By now, we're all used to Nintendo's well-established act of pretending that event legendaries don't exist until they're ready to distribute them. While Pokémon Diamond and Pearl were released in September 2006, Arceus wasn't officially revealed to Japanese fans until February of 2009. But in Mew's case, they had a good reason for not revealing it: they didn't know it existed.
Although the first generation of Pokémon games contain a handful of references to Mew as the mysterious creature used in the creation of Mewtwo, there was no plan for it to appear in the games. However, at the end of the development of Red and Green, programmer Shigeki Morimoto noticed that there was enough room for one more Pokémon, following the removal of the debugging tools. And so, Mew itself was quietly inserted into the code, and although the higher-ups at Game Freak were all aware of the new hidden content, Nintendo wasn't. Mew couldn't be accessed through normal gameplay and, as Morimoto put it, "Unless we could think about any good opportunity to do so, the existence of Mew wouldn’t have been revealed to the public. It was left in there in case it was suitable for some post-launch activity."
Mew might have remained a secret forever were it not for certain bugs in the games that led some players to discover its existence. As rumors of a hidden Pokémon began to spread, Nintendo capitalized on them by launching the "Legendary Pokémon Offer" in CoroCoro Comic. Twenty winners would be selected to have Mew put on their game cartridges, and there were around 78,000 entrants. Nintendo and Game Freak have both indicated that this was the turning point for Red and Green, lifting them to best-seller status.
Mew definitely had a role to play in the growing popularity of the Pokémon franchise, and its place in the in-game universe is equally important. It is often described as the ancestor of all Pokémon, although this phrasing wasn't used until Pokémon Crystal, where it can be found in Mew's Pokédex entry. Prior to this, in Pokémon Silver it was stated that "Its DNA is said to contain the genetic codes of all Pokémon", which was used to explain Mew's ability to learn all TM moves. In the whole of the first generation, however, no statements were made regarding Mew's relation to other Pokémon. This is interesting, because it seems that Mew wasn't originally conceived as the ancestor of all Pokémon at all. Instead, this is an idea that seems to have gradually developed over time. To see why the designers arrived at this decision, let's take a look at Mew's appearance.
In the games, Mew seems to have been the template upon which Mewtwo was based. Mewtwo was an enhanced Mew: bigger, stronger and meaner. And so, it follows that Mew would resemble Mewtwo in many ways... but to emphasize the changes that have been made, Mew is much smaller and cuter, with a definite softness to its design. Most notably, however, there are many aspects of Mew's design that are lifted from the process of embryogenesis. It's smooth, pink, has a large head, and is often depicted in a uterus-like bubble. What better way to represent the prototypic form of Mewtwo than by using the prototypic form of life itself?
So, how did Mew make the leap from being simply the embryonic version of Mewtwo to the predecessor of all Pokémon? It's actually not that hard a connection to make. For many years, scientists have noted that, during the early stages of human development, the embryo goes through stages reminiscent of other creatures. During very early development, for example, we have what appear to be tails. In the 18th and 19th centuries, when biologists were beginning to wrestle with the notion that all life may have had a common ancestor, some took note of these seemingly animalistic stages in human development, and wondered if they might be related to the process of evolution.
We associate Charles Darwin with evolution, but he wasn't the first to propose that animals changed over time, gradually becoming new animals. What Darwin did that was so revolutionary was to propose a mechanism for these changes: natural selection. This wasn't the first mechanism that was considered, and a popular theory before Darwin's rise to prominence was Lamarckism. This theory stated that creatures changed in response to their environments, and then passed on those changes to their offspring. The classic example given is the giraffe's neck. Lamarckism stated that giraffes had to stretch their necks to reach the leaves on treetops, and then passed these stretched necks to their young, meaning that each generation would have a slightly longer neck than the last. It made sense at the time, and it seemed to be a good way of explaining how evolution might actually work. In time, though, this theory was disproven, and replaced by Darwin's concept of natural selection, in which animals that aren't suited to their environments simply die off, whereas those that are, perhaps due to natural variation in the population or a fortuitous mutation, get to thrive and reproduce.
Lamarckism is of interest to us because it influenced the thinking of many scientists before and even after natural selection was proposed as an alternative. It really wasn't until the early 20th century, when we gained a fuller understanding of what genes were and how they passed on characteristics, that we could say with confidence that natural selection was the driving force behind evolution. Up until that point, many scientists were influenced by Lamarckism, and we can see some of these ideas at work in Ernst Haeckel's recapitulation theory.
Recapitulation theory was often as expressed as "ontogeny recapitulates phylogeny". What this meant was that a creature's development (its ontogeny) reflected the evolution of its species (its phylogeny). Humans, for example, are descended from smaller mammals, which were descended from reptiles, which were descended from amphibians, which were descended from fish. Haeckel's idea was that the human embryo, as it develops, goes through stages resembling these ancestral forms. Just as Lamarckism argued that creatures could change themselves and pass these changes to their offspring, recapitulation theory claimed that one could see these changes happening: millions of years of evolution being repeated in what was, by comparison, the blink of an eye. Haeckel produced drawings of the embryos of different species at different stages of development; drawings which apparently showed a high degree of similarity between said embryos.
Unfortunately, science is rarely ever that straightforward. Closer observations showed that these "ancestral stages" really weren't there. They were simply the result of some overly-selective observations. Even Haeckel's drawings turned out to have been deliberately fiddled in order to emphasize similarities between embryos. Rather annoyingly, images directly based on these drawings can still occasionally be found in modern textbooks, despite having been discredited long ago. The authors should, frankly, know better.
But perhaps we shouldn't be too hard on poor old Ernst Haeckel. We remember him for what he got wrong, but he did make some important contributions to the biological sciences. He was responsible for coining terms like 'ecology', 'phylum' and 'phylogeny' – all of which are now commonly used by biologists. And while recapitulation theory was rejected, there are some elements of it that might just hold true.
During development, it's been noted that certain features that have been around for many millions of years often appear in the embryo sooner than more recently evolved ones. The backbone, for example, appears very early in human development, and there's no doubt that it's a very ancient structure. The reasons for these observations still aren't well understood, though, and there's no doubt that any relationship between embryonic development and evolutionary history is far subtler than the model Haeckel proposed.
The correlation of the embryo (symbolizing our origins as individuals) and evolution (symbolizing our origin as a species) remains a very strong one, though, and we can see this in the design of Mew. In fact, Mew could be seen a sort of mirror image of recapitulation theory. Rather than an embryo resembling ancestral forms, Mew is an ancestral form that resembles an embryo.
And let's not forget that Mew is supposed to be the ancestor of all Pokémon. This mirrors the concept of the universal ancestor: an organism in the very distant past from which every living thing today is descended. We don't really know anything about it (although we can theorize), but we do know that it must have existed. As different as we are from birds, fish, plants and bacteria, we know that we must all be related to each other because there are certain very complicated things that we all have in common. We all have cells. We all use DNA and RNA to make proteins, and we all do it in exactly the same way. It would be far too big of a coincidence for these things to have arisen independently: some fiendishly clever mathematicians recently calculated that a single, universal ancestor is 102860 times more likely than life having come from multiple sources.
What might this organism have been like? It's estimated to have existed between 3.5 and 3.8 billion years ago. It would have to have been a single-celled organism, resembling a bacterium, and it would have reproduced through cell duplication. We can also assume that its genome (the sum total of its DNA) would have been very small, just like those of modern bacteria.
And this brings me to the one slightly irksome thing about Mew... well, irksome to a pedantic biologist like me, anyway. "Its DNA is said to contain the genetic codes of all Pokémon." But if Mew came first and all other Pokémon are descended from it, how could that be? The notion that Mew was there at the dawn of life, with all the genomes of every Pokémon that would eventually appear stored away inside it, is a little too close to the false idea that evolution moves in a predetermined direction. Biologists are fighting back against this misconception all the time, and even the slightest hint of it sets my nerd-senses tingling.
I can forgive Mew, though. How could I not? What began as little more than a prank ended up transforming the fortunes of the Pokémon franchise. And not only that; it's given me an excuse to talk about three obscure biological theories. There are not many Pokémon that I could say that about... but Mew is a very special Pokémon.