Recently, a SF&F user asked this question, about Inhumans vs. Mutants in the Marvel Universe. With the arrival of the Inhumans in Marvel’s Agents of S.H.I.E.L.D. (and an upcoming movie), and Scarlet Witch and Quicksilver’s appearance in two separate movie universes, its a topic that has generated a bit of interest.
This post is an expanded, more in-depth version of my answer to that question. There’s a lot more to Marvel’s mutant population than just mutants and Inhumans, and things can get confusing. Unfortunately, as with most things Marvel-related, it not a simple question to answer. What constitutes a mutant? How many kinds are there? What’s the difference between them? Are they different species? Here, I’ll try to answer all of these questions and more.
One note on the cinematic universes: there are a lot of movie universes based on Marvel material, but I’m only going to discuss two of them here: Earth-199999, the Marvel Cinematic Universe, and Earth-10005, the X-Men Cinematic Universe. These are the only two large-scale cinematic universes that are still active; as far as I am aware, none of the other (now-defunct) movie universes included any type of mutated human. This includes the two Spider-Man universes, the two Fantastic Four universes, etc, all of which I’ll be ignoring from here on out.
The biggest source of confusion, when discussion Marvel’s mutant populations, is that the word does not mean the same thing in the Marvel universe as it does in ours. Lets start by getting a quick definition of what mutant means, in real-world biology, and see where that takes us. According to Wikipedia:
Per this definition, any group of beings who’s genome is a mutated version of Homo sapiens sapiens is, strictly speaking, a mutant. For the purposes of this post, I’ll be using this definition of the word “mutant” to mean all such groups, and more specific terms to identify members of any particular mutant human population.
The question of whether Marvel’s various mutated races are their own species or not is a bit of an open question, both in-universe and out-of-universe. Partly, this is because the line between species and subspecies is quite blurry, and is determined by many factors beyond simple genetics (including geography, ecology, behavior, and in some cases even politics). Characters such as Magneto, for example, consider themselves to be a different species from humans because it fits their agenda better. However, it’s not clear that such a designation is warranted — Magneto had human parents and had children by a human mother. In modern Marvel comics, it’s common to see members of the human-derived races classified as subspecies of humans, though it is different for different groups. I’ll go into more detail on this aspect as we talk about each group.
Marvel’s Main Mutants
In the Marvel universes, when you use the word “mutant“, you mean something quite a bit more specific than biologists would like:
an organism (usually otherwise human) who possesses a genetic trait called an X-gene that allows the mutant to naturally develop superhuman powers and abilities.
These are the humanoid mutants that you see in the various X-Men and related titles. Unless you’re specifically talking about genetics, if you say “mutant” to a Marvel fan, they assume you mean this kind of mutant. They are usually identified as a subspecies of humanity called Homo sapiens superiorUncanny X-Men (1963) #1</a”>2, while during the House of M story-line, Mister Sinister identified them as Homo mutatisthis post among many others on the site for the gory details why. The end result: no one in the MCU has the X-gene, and you’re unlike to hear the word “mutant” in a Marvel Studios movie anytime soon.
The Inhumans are a race of people that were genetically engineered by the Kree, tens of thousands of years ago, when Homo [sapiens] neanderthalensis was first emerging as a species. The Celestials interference in proto-human development left a genetic imprint on those developing species, which the Kree took advantage of. They were experimenting with ways to produce weapons to use in the Kree/Skrull war, and their tinkering produced a race of humans with the genetic potential to develop super-human powers. The project was eventually shut down by the Kree Supreme Intelligence, but the test subjects on Earth managed to escape detection, and formed their own society.
The Terrigen gene, unlike the X-gene, does not activate itself automatically. Rather, it requires exposure to a mutagen called Terrigen Mist, which the Kree’s genetic manipulation left the Inhumans susceptible to. The Inhumans are highly focused on the concept of genetic purity — they keep track of every mutation from each family line and work hard to prevent the most dangerous or destructive mutations from happening. Exposure to the mists is a privilege given only to those deemed worthy. Once exposed, Inhuman mutations are extremely similar to X-gene mutations in type, variety, and power (to the point where it is difficult to tell them apart without genetic testingInhumanity #1</a”>5, putting them in an entirely different genus than humans. This seems strange, given how incredibly human they seem. In fact, prior to the Infinity story arc, thousands of inactive Inhumans (or human/Inhuman hybrids) were living all over the world, alongside humans for millenia. It doesn’t seem like these Inhumans had any significant problems appearing human — no medical tests uncovered them, they didn’t stand out as unusually healthy or sick, and they seemed more than capable of having children of their own.
The Inhumans have appeared in most Marvel universes, but not in Earth-10005 (the X-Men cinematic universe); they are restricted cinematically to Earth-199999.
Deviants and Eternals
We’ve already seen how the Celestials interference with proto-human genetics lead to both Inhomo supremis and Homo sapiens superior. More directly, however, the Celestials genetic engineering created two additional mutant races: the Eternals and the Deviants.
Unlike the other mutants, Eternals and Deviants are born with their mutations already expressed. Eternals appear superficially human, but have a similar set of mutated abilities: psionic powers, energy manipulation, and near-immortality. The Deviants, on the other hand, were engineered to mutate rapidly, making each Deviant nearly unique. (The rate of mutation is said to be far more random than even X-gene mutants).
The Eternals have been identified as the species Homo immortalisfirst non-human species to ever appear in the Marvel universe, and yet their origins are pretty unclear. This species somehow evolved, either from Homo sapiens or from a common ancestor, to have a set of aquatic adaptations. They have gills, are adapted for high pressure environments, and have vision more sensitive to colors seen underwater. They cannot naturally breathe air for more than a few minutes. They also have enhanced strength and speed (underwater, at least), and heightened senses.
There are currently two groups of Homo mermanus in the Marvel universe. The majority of them live in the underwater city of Atlantis, found somewhere in the Atlantic Ocean. This is their ancestral home, and currently houses their capital and their King, Namor the Sub-Mariner. A splinter group of Atlanteans migrated to the Pacific Ocean and settled in the sunken northern portion of the continent of Lemuria, where they live along side the Deviants that control it. These two groups have often been at odds with each other, but when threatened by outside forces, Namor has also been known to come to their defense.
Homo mermanus very rarely interact with other humanoid species, due to geographic and ecological isolation. The notable exception is King Namor, who participates in diplomatic relations with other countries as needed. Namor is actually a human/Atlantean hybrid, meaning he can breathe both underwater and on land. He is also an X-gene mutant, making him one of the most powerful creatures on Earth-616.
Homo mermanus have appeared in both the Earth-616 and Earth-1610 universes, but thus far, have not appear in any cinematic universe. (In the absence of more information, it’s assumed they would be restricted to Earth-199999.)
Homo Genus Hybrids
Within the Marvel universe, the exact biological status of these various type of human mutants isn’t very clear. If we assume that Marvel scientists use the same binomial nomenclature as real-world scientists, then many of these beings would be their own species, and in at least one case, it’s own genus. That would imply that there has been significant enough genetic drift to make cross-species offspring impossible, or at the very least, sterile.
With the Atlanteans, this does appear to be the case. While there are a number of Atlantean hybrids, they are often mentioned as being sterile. In some cases, they have resorted to cloning or other artificial means to produce children. On the other hand, while Namor himself was claimed to be sterile at one point, he later to have fathered natural children. It’s possible that his also being an X-gene mutant may have played a role.
There are tons of human/Inhuman hybrids dating back dozens of generations (the current Ms. Marvel, Kamala Khan, is such a hybrid). Other combinations are much more rare, but not unheard of. There is at least one Inhuman/mutant hybrid: Luna, daughter of Quicksilver (an X-gene mutant) and Medusa (an Inhuman). Another notable hybrid is Thane, the son of Thanos (an Eternal), who’s mother was an Inhuman. There also is at least one case of a second-generate hybrid, with an Inhuman mother and a hybrid Inhuman/Deviant father. This kind of fertile hybrid seems highly unlikely if the parents aren’t even in the same genus. (More likely, the term Inhomo supremis was chosen arbitrarily, and would be more appropriately Homo sapiens inhumanus or something similar.)
In general, the hybrid offspring of humans tend to favor their non-human parent, while hybrid offspring of the other races tend to be some mixture of their parents super-human abilities. Thane, for example, seemed human at first, but upon exposure to the Terrigen mists, began to demonstrate some small portion of his father’s Eternal powers. Sometimes the mixture strongly favors one race over the other. Inhumans hybrids, for example tend to appear human until exposure to the Terrigen Mists, at which point they may start demonstrating a mix of powers from their parent (as was the case with Thane). Other times, the children are a true hybrid of their parent, such as with most human/Atlantean or mutant/Atlantean hybrids, which are amphibious and often stronger than either parent’s race (again, Namor being a prime example).