[Theory] What Are Pikmin? - Originally posted on /r/GameTheorists.
Before we try to answer “What are Pikmin?” we need to define the characteristics of plants and animals to determine which category Pikmin fall into.
An animal is a multicellular eukaryote, meaning that it’s made up of multiple cells which have membrane-bound organelles—including a nucleus—and undergo meiosis and mitosis. The characteristics that differentiate it from plants are its nervous and muscular systems, its motility, and its heterotrophy. Unlike plants, which are sessile and thus convert radiant energy into chemical energy to make their own sugars, animals can actively move to acquire nutrients. [1]
A plant is also a multicellular eukaryote, differing in that its cellular membranes are structures called cell walls, made of various polysaccharides. Turgor pressure inside the cells is maintained by the osmotic flow of water. These changes in turgidity cause the plant to stay rigid or wilt. Plants are autotrophs, utilizing photosynthesis to create their own glucose, and their reproduction centers around an alternation of generations lifecycle (gametophyte and sporophyte). Roots function in nutrient and water uptake, and anchorage to the ground. [1]
In broad, general terms, the defining characteristics that separate these two taxa are motility/sessility, tissues/organ systems, cell structure, means of nutrient acquisition (the type of -trophy), and reproduction.
With that information in mind, let’s take a look at the Pikmin as they’re presented in-game and isolate their immediate characteristics.
The overall morphology is consistent across the seven species of Pikmin—each has a humanoid, bipedal body plan with three digits on each limb. On the Pikmin’s head is a stalk sheathed in skin, with a plant-like structure protruding at the end. When inactive, Pikmin display partial bioluminescence. Each species has its own unique adaptations: Red Pikmin have a nose-like protuberance and external fireproofing; Yellow Pikmin have ear analogues, insulating proteins (?) for protection against electrocution, and a tolerance to higher altitudes; Blue Pikmin have an opening functionally similar to gills; Purple Pikmin have increased girth and physical strength, and hair-like structures on their heads; White Pikmin have compound eyes, resistance to airborne toxins, and aposematic coloration; Rock Pikmin have a calcified epidermal layer; and Pink Pikmin have wings and compound eyes.
Captain Olimar’s journal from the first two games refers to them as a “plant-animal” species. What this means is rather vague, as the games don’t elaborate much beyond the original flavor text. This leaves us to assume three possibilities: Pikmin are (1) animals with plant-like qualities, (2) plants with animal-like qualities, or (3) an entirely new kingdom of organisms, descended from neither Plantae nor Animalia.
Theory 1: Pikmin are animals.
At a glance, Pikmin biology is closer to animals than plants: they’re motile, have a fight/flight reflex, ingest food (nectar, egg yolk), possess nerve and muscle tissue [2], exhibit intra- and interspecific social behavior, vocalize, and react to tactile, auditory, and visual stimuli. The fact that Pikmin can forage for food would negate the need for being autotrophic, suggesting at first glance that Pikmin are merely animals exhibiting plant mimicry and don’t actually photosynthesize. If this is true, then the Creeping Chrysanthemum would also fall into this category. Real-world animals that employ mimicry of plants include stick insects, flower mantises, and several species of caterpillar.
You’d think it’s an open-and-shut case, and that Pikmin are just animals mimicking plants. However, more evidence from in-game sources suggests otherwise.
Theory 2: Pikmin are plants.
Many Nintendo classics do a good job skirting around the topic of sex: whether it’s Mario getting some “cake” from Peach, or the Daycare Couple finding Pokémon eggs and having no idea where they came from, Nintendo has always been pretty coy about the horizontal hula. The Pikmin series continues this trend by facilitating Pikmin reproduction via the Onion. While this was done largely as a game mechanic to bolster the player’s army, the franchise lore implies that the Onion directly oversees this process. Various organic matter is brought to the Onion by Pikmin—be it vegetation or slain animals—and the Onion uses the energy from these resources to convert them into new Pikmin, which are identified by Olimar as “seeds.” Seeds are a reproductive feature unique to angiosperms (flowering plants), which Pikmin could allegedly belong to given the floral structure on their head. The “seeds” also come from a fruit (the Onion) like they would in real life, lending some credibility to the theory. More evidence that Pikmin are plants comes from Olimar, who refers to the Pikmins’ feet as “ambulatory roots,” implying that they’re not chordate limbs, but rather roots that have evolved for locomotion. Their usage as walking appendages could be an example of exaptation of their original function (nutrient and water uptake in the soil), which Pikmin still partially do when buried in a substrate. (It’s worth noting that Olimar isn’t exactly the most reliable source when it comes to biology, when you consider that he mistook an LED for a species of bioluminescent plant.[4]) There are cases of plants displaying “movement,” such as the Venus flytrap shutting when something touches its trichomes, or when plants engage in phototaxis (orienting themselves toward the sun). However, these “movements” are reactionary responses to external stimuli, not conscious intentional locomotion. In order for a plant to truly be motile, it would need to have muscle and nervous tissue, which are features exclusive to animals. So…that makes this evidence void, I guess?
The main argument for Pikmin-are-plants stems from the flower atop their heads. (Get it? “Stems”? Like the stalks on plants? Areyouproudofmyshittypun,Matt?) Flowers are a reproductive structure unique to a monophyletic group that evolved only 130 million years ago. [5] The male gametes are housed within pollen grains produced in the anther, while the female gamete is housed in the stigma. Pollination results in the ovule being fertilized by the sperm and developing into a seed, while the ovary wall (the pericarp) becomes the fruit. To grossly oversimplify the gametophyte lifecycle, after pollination the flower turns into a fruit. This leads us to the glaring problem with the Pikmins’ flower: it doesn’t bear fruit. Like, ever. Nor does it have any signs of carpels or stamens. You could argue that the flower has evolved to not function as a reproductive organ since the Onion takes care of that, but that defeats the entire purpose of the flower’s existence. From an evolutionary perspective, it would be incredibly wasteful to invest energy into developing a vestigial structure with no reproductive value.
So while there might be some evidence alluding to Pikmin being plants, we’ve proven on a biological basis that this is highly unlikely. And we’ve also shown that you can’t take the game’s own word that Pikmin are plants, given Olimar’s unreliability to identify plants in the first place.
Theory 3: Pikmin are a new kingdom of organisms entirely, not descended from Animalia or Plantae.
This is the least likely of our theories simply because an organism evolving an amalgamation of animal/plant traits would be inefficient and functionally redundant. While evolution is a random process that doesn’t follow any discernable patterns, there are some consistencies we can rely on to explain why this model of organism would be inefficient. It’s the same explanation for why plants today haven’t evolved feet and digestive organs—they don’t need to. They already synthesize their own glucose from a guaranteed, permanent energy source, the sun, so why would plants that waste energy by evolving needless adaptations be selected? There are very few environmental pressures that could force a plant to evolve analogous animal characteristics for nutrient acquisition. Pitcher plants and flytraps are among the few uncommon examples of carnivorous plants that were forced to adapt to low-nitrogen boggy soil, and “feed” on external nitrogen sources such as arthropods. [6] Examples like the aforementioned are the exception, not the rule. A plant wouldn’t need to move if it grew in a location with a guaranteed source of sunlight, and trying to pursue and actively accrue nutrients like a heterotroph does would waste the ATP it makes from photosynthesis.
The differing, separate characteristics of plants and animals exist simply because each evolved to fulfill a different niche, as autotrophs and heterotrophs. Optimizing their respective specializations is why these two different kingdoms coexist, and why a tertiary kingdom with animal and plant adaptations doesn’t exist at all.
So, is that it? Are Pikmin just animals mimicking plants? If Occam’s razor is to be believed (or in this case, Occam’s shearing prunes), the simplest solution is the correct one.
Nintendo, in its haste to overhype a unique feature in its games, promoted Pikmin as animal-plant hybrids, without doing any of the scientific research. I guess Pikmin are just glorified animals—
Wait. Aren’t we forgetting something?
This would be the foregone conclusion if it weren’t for the wildcard. A simple, easy-to-overlook enemy that debuted exclusively in Pikmin 2, and elevated the Pikmin from the status of being just an animal, to singlehandedly redefining what the word “Pikmin” means.
Ladies and gentlemen and nonbinary viewers, may I introduce the eighth Pikmin species: the Bulbmin.
In the underground dungeons of Pikmin 2, Bulbmin can be found patrolling throughout the various sublevels. What makes them so special is that unlike their adorable monochromatic cousins, Bulbmin resemble one of the most iconic enemies in the game: the Red Bulborb. This polka-dot mouth-on-legs is a solitary animal, occasionally seen with groups of breadbug mimics foraging nearby for protection. Where Bulbmin and Red Bulborb differ is that the Bulbmin have a complex social structure like the Pikmin, and aggregate in large cooperative groups with adults and juveniles. And, like the Pikmin, a flowering plant (Chaenostoma cordatum) sprouts from their backs. In Olimar’s notes, he describes the Bulbmin as “a parasitic form of Pikmin that has infected a Bulborb,” that “[buries]…into the nervous system of the host Bulborb and [infuses] it with natural hormonal excretions.” [7]
What an oddly specific word choice. Parasite.
Perhaps we’ve been looking at Pikmin incorrectly this entire time. For years, we assumed that Pikmin were singular individuals because the games said so. But what if they’re wrong? What if “Pikmin” doesn’t refer to an organism, but rather the relationship between two different organisms?
What if the word “Pikmin” refers to a type of symbiosis?
Theory 4: Pikmin (and Bulbmin) are an obligate mutual symbiosis between a plant and animal host.
Let’s quickly overview the three types of symbiosis so we can determine what the relationship between the animal and plant is.
Mutualism is a symbiosis that benefits both species involved. An example includes the relationship between sharks and remoras.
Commensalism is a symbiosis that benefits one of the species in the relationship, while the other is unaffected. An example includes the relationship between clownfish and anemones.
Parasitism is a symbiosis that benefits one of the species at the expense of the other. An example includes the relationship between ticks and deer.
The idea of plants and animals having complex relationships isn’t new. One such example is an order of sea slugs called Sacoglossa. The slugs are better known as sap-suckers. Sacoglossans ingest algae and store the partially-digested chloroplasts within an organ called the diverticulum. The chloroplasts continue to photosynthesize inside the sea slug for a while after, in a process known as kleptoplasty. The host sea slug reaps the benefits of the phagocytosed chloroplasts, and in the process earned the nickname “the solar-powered sea slug.” [8]
A lettuce sea slug, Elysia crispata.
The aforementioned relationship is a predator-prey interaction, however, not a symbiosis. Let’s try something a little closer to home. The fungal genus Cordyceps mentioned in the What Are Toads? episode is a pretty good example. To recap, its mycelium slowly take over the body of the host arthropod, compelling it to travel to an area of adequate humidity and temperature so the fruit body (the asocarp) can emerge from the body of the host. Sound familiar?
“So what?” I hear you say. Are we to assume that some species of plant parasitizes Bulborbs and Pikmin (hereafter referring to the animal, not the symbiosis unless specified otherwise)?
Maybe. But let’s take it one step further. The game portrays the Bulborb’s relationship with the plant as harmful, but what if it’s the exact opposite? The plant modifies its host’s behavior, making it socialize with conspecifics instead of isolating itself. Group survival has been known to correlate positively with increased individual longevity. The plant is indirectly benefiting the Bulborb by giving it a social structure. This could be seen as commensalism (the Bulbmin benefits, and the plant is unaffected), but I want you to consider this: Bulbmin live underground. How is a plant going to photosynthesize without access to sunlight? The answer is that the plant doesn’t.
Meet Rhizanthella gardneri, or the western underground orchid. This endangered flower doesn’t photosynthesize because it spends its entire life buried beneath the dirt. [9] In order to obtain energy and nutrients, the orchid forms a myco-heterotrophic symbiosis with a species of fungus called Thanatephorus gardneri and a plant called the broom honeymyrtle (Melaleuca uncinata). By siphoning nutrients from the fungus and plant, the orchid can thrive underground, and consequentially it lost the genes responsible for encoding chloroplasts. [10] Applying the orchid’s evolution to the flower and the Bulbmin, we see how the Bulbmin benefits by attaining a social structure it otherwise wouldn’t have, and how the flower benefits by having a host it can borrow nutrients from in order to survive underground.
Thus the Bulbmin isn’t a single organism, but rather a chimeric obligate symbiosis between two unrelated species. So how does this apply to the traditional Pikmin that we gleefully catapult into the maws of hungry beasts? I’m getting there.
With the exception of Purple and White Pikmin, the remaining five species are terrestrial. The flowers on the Red, Yellow, Blue, Pink, and Rock Pikmin are exposed to sunlight, so you’d think that they’d have no need to evolve a mutualistic relationship with an animal host, right?
Well, it’s never been officially confirmed, but the presence of human-made objects (batteries, cardboard boxes, bottle caps) on PNF-404 and the presence of a globe in Pikmin 2 strongly suggest that the planet is meant to be Earth. The unfamiliar species of animals imply that millions of years must have passed in order for them to have evolved. This idea is reinforced by the absence of humans, and the remains of what look like pavement and bathrooms reclaimed by nature.
I ask you, what happened to cause humans to go extinct? The games are ambiguous, but we can make an educated guess. In Pikmin 1, Captain Olimar locates the Geiger counter that fell off of his ship the S. S. Dolphin when it crash-landed. The in-game description for the item says that it “goes wild and lets out a lot of noise.” [11] It’s likely that a human-caused nuclear event happened on a global scale, eradicating our species and irradiating the planet.
So, how does this come back to the Pikmin?
Radioactive elements and heavy metals can kill plants in high quantities. Take the Lehigh Gap, a Superfund site heavily contaminated by cadmium, zinc, and lead. The uptake of radioactive isotopes by the roots of plants within the vicinity resulted in massive deforestation and overall widespread vegetation loss. While the Lehigh Gap Restoration Project has made incredible progress restoring the area since its 2005 initiative, the devastation caused by these metals demonstrates how harmful they can be to plants. [12]
In a world heavily irradiated by nuclear warfare, it would make sense that since plants can’t use the soil as a substrate for their roots, they’d turn to the next best option—relying on an animal host. The obligate mutualistic symbiosis between the flower Chaenostoma cordatum and Pikmin is the result of millions of years of coevolution. Even after radioactive contamination subsided over the course of thousands of years, and the environment was able to sustain vegetation, the plant and the Pikmin retain their relationship. The plant has lost its need to photosynthesize, although it still retains its vestigial cotyledons, which emerge shortly after the Pikmin host is born, only to quickly undergo abscission as the flower develops. The rest is conjecture, but it’s possible that the Onion (the fruit) and the flower on the Pikmin’s head are a variation of Chaenostoma cordatum’s alternation of generations lifecycle, with reproduction that is separate from the actual Pikmin’s. Newborn Pikmin acquire their plant by eating the seeds produced by the Onion, which in turn germinate inside the Pikmin. Over the course of the Pikmin’s life, the plant will rapidly grow inside its body, its roots spreading and intertwining with the host’s nervous system. When buried in the ground, the roots in the Pikmin’s feet can react to the presence of soil and temporarily emerge from the host body to bury into the earth. This gave rise to Olimar’s description of them as “ambulatory roots.”
Only after the Pikmin host dies does the flower reach sexual maturity. It lives off of the detritus from the decomposing body of its host, and after its ovules are fertilized by the pollen grains does the fruit (or Onion) grow. Pikmin colonies come to inhabit the Onion and defend it with their lives, much like leafcutter ants do with myrmecophytes. Pikmin, like all animals, reproduce sexually, rearing their offspring with nurseries inside the Onion until the offspring have ingested a seed from the Onion and begun their symbiosis.
But hey, it’s just a theory. An unofficial Game Theory!
Integrated Principles of Zoology (14 ed.).
Pikmin 2. Piklopedia entry for the Pellet Posy.
Pikmin 2. Piklopedia entry for the Creeping Chrysanthemum.
Pikmin 2. Piklopedia entry for the Glowstem.
Encyclopedia of Life. “What is a Flowering Plant?”
Wikipedia. Carnivorous plants.
Pikmin 2. Piklopedia entry for the Bulbmin.
Bougoure, Jeremy et al. 2010. Carbon and Nitrogen Supply to the Underground Orchid, Rhizanthella gardneri. New Phytologist 186: 947-956.
Delannoy, Etienne et al. 2011. Rampant Gene Loss in the Underground Orchid Rhizanthella gardneri Highlights Evolutionary Constraints on Plastid Genomes. Molecular Biology and Evolution 28 (7): 2077-2086.
Pikmin 1. Item description of the Geiger Counter.
Hoopes, Robert. Five Years Ago and Back to the Future: How the Lehigh Gap Restoration Project Turned Around a Stalled Superfund Initiative.
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