Are the X-men Mutants “the Next Step in Evolution?” (RIP Stan Lee)

Are mutant the next step in evolution? Yes!  (But not like that.)

[This essay first appeared in AiPT!.]

In the Marvel universe, the X-men are a special class of human beings called mutants, so called because they harbor mutations gifting them with various superhuman abilities. Each hero has a particular superpower generated, presumably, by specific mutations in their genomes.


Stan Lee (peace be upon him), Jack Kirby, and the other Marvel writers “took the cowardly way out” (their words) and chose not to think up elaborate origin stories for these heroes, and instead pinned their abilities to unnamed mutations. We can only speculate about the underlying anatomy and physiology of these super powers. And speculate we will.

What are mutations?

But first, a word about mutations. Lee was definitely on to something when he posited that mutations were the way to deliver new abilities to an otherwise run-of-the-mill human being. In fact, mutations have been the vehicle of all evolutionary innovation since the first proto-cells floated aimlessly through the primordial soup. That’s an understatement, actually, because mutations have been the source of all heritable changes, innovative and mundane – and the mundane far outnumber the innovative – in all lineages of life.

Screen Shot 2018-11-10 at 9.31.22 AM Mutations are most often the result of copying errors during the process of DNA synthesis. Every time a cell divides, it must first copy its DNA so that both daughter cells get all the genetic instructions. The copying mechanisms are pretty darn good so mistakes are rare, but they do happen. And when they do, they are almost completely random. This is as true in the simplest cells on earth as it is in our elaborate ones. Most mutations are harmless, however, and we all have them. In fact, each of us adds a couple hundred new mutations to the human gene pool. If Dr. Bolivar Trask’s “mutant detector” from X-men: Days of Future Past were ever actually fired up, it would go off constantly. 

The X-genes

In the case of the X-men, the mutations in question are those that unlock the function of previously dormant “X-genes.” This, too, is based on a real biological phenomenon. Mutations that activate or deactivate a previous mutation are called spontaneous revertantsand these individuals, while incredibly rare, probably played key roles throughout evolutionary history. Scientists have generated many spontaneous revertants in laboratories including chickens with teeth (bird ancestors lost their teeth over 80 million years ago). More helpfully (and less frighteningly), scientists have activated a dormant gene that enhances oxygen transport by hemoglobin, a technique that may help treat a variety of anemia-causing diseases. And revertants are not limited to laboratory creations. A wild dolphin with “hind fins” was discovered in in the Pacific Ocean in 2006 (dolphin ancestors lost their hind limbs 40 million years ago).


Mutations that occur in regular cells of your body, even if they do something great for you, are not the engines of evolution because you don’t pass those on. Only mutations in the germ line – the cells that give rise to sperm and eggs – matter in the long run. So, in real life, an evolutionary “mutant” didn’t actually experience said mutation herself: one of her parents did in their gonads. (A women’s eggs are mostly pre-formed way back when she was an embryo in utero herself, so a maternally inherited mutation is one that occurred when one’s grandmother was pregnant with their mother!)

But X-men don’t get their powers until puberty. To get around the problem that mutations in regular body cells can’t “spread” to other tissues, it was explained that when the X-genes are first activated (in which tissue, we’re not told), they express proteins that subsequently mobilize, making further mutations and alterations in genes and cells throughout the body. While this scenario is exceedingly far-fetched, it’s reminiscent of a principle that we now recognize as epigenetics: some factors can affect the expression of other genes in a stable, cascading, and even heritable way. Presciently, this X-men form of super-genetic inheritance was first discussed in the X-men comics in the 1960s, a full 30 years before the scientific community began to appreciate epigenetics.

How do genes give rise to powers?

To discuss how these mutations have their dramatic “EX-tra powers,” we have to fully depart from scientific reality. In the real world of evolutionary history, mutations are random and generally emerge one-at-a-time. This means that mutations can only make the tiniest tweaks and tugs in the bodies in which they occur.

Screen Shot 2018-11-18 at 9.50.44 PM

Going from no wings to fully formed wings in one generation is simply not anatomically possible, even theoretically. Besides the creation of new anatomy out of whole cloth (something that never happens), it would also require dramatic changes in the nearby skeleton, musculature, nerves, and connective tissues. And don’t forget the requisite changes in the brain! The mutants will need new neural circuitry in order to operate their new features. Again, this is way more work than mutations can do, even millions of simultaneous ones.

In fact, growing whole new structures is so rare that it has hardly ever happened, over the entire half billion years of animal evolution. In vertebrates, wings have evolved three separate times – in birds, bats, and pterosaurs – but all of these involved the reshaping of the pre-existing forelimbs, not the growth of new appendages from nothing. Yet, growing entirely new structures is the hallmark of our X-men.

Of course science fiction is not meant to be perfectly accurate in its scientific content – that’s the “fiction” part and also what makes it fun. However, there is one error that is based on a misconception so heretical and so widespread that it simply must be called out every time. The mutant Armando Muñoz gets the nickname “Darwin” because he can adapt – biologically, no less – to any new environmental challenge that he’s faced with.Screen Shot 2018-11-18 at 9.53.46 PM

This is basically the opposite of how evolution works. Individuals do not, indeed cannot, adapt. Populations adapt over many generations when the randomness of mutation collides with the non-randomness of natural selection. Further, the act of presenting an environmental challenge to a population doesn’t make them adapt. Instead, they must wait around for the rare and random mutation that helps them in some tiny way and then, over time, they can begin to adapt. It’s a slow, aimless, and utterly unsatisfying process.

The rules are obviously different with these fancy X-genes, but this ill-suited namesake would make Darwin roll in his grave precisely because of how hard he worked to differentiate his theory from prior ideas that posited, incorrectly it turns out, that individuals can adapt.

The inheritance of the X-genes

Professor X once claimed that the X-gene itself is on the X chromosome (because of course it is). But this creates a major problem for the inheritance of mutant abilities. While female mutants can pass their X-gene on to both sons and daughters, male mutants would only pass their mutation on to their daughters because fathers pass only their Y chromosome to their sons, not their X. Since Magneto is known to have sons with his same abilities (e.g., Quicksilver), Professor X must have been wrong about the location of the X-genes after all.

Screen Shot 2018-11-18 at 9.56.53 PM

An interesting question is how different mutant superpowers would combine in individuals with two mutant ancestors. The fantasy is that all the powers would accumulate as the mutant family trees entangle. However, this assumes that the various mutations involved will harmoniously comingle in the body. It’s much more likely that they will counteract each other in destructive ways.

For example, in order to effectively manipulate magnetic fields, Magneto needs a reorganization of his cerebral cortex and probably other brain regions also. Those same brain centers would likely be required to operate other mutant powers and so the mutations become incompatible at the level of brain tissue architecture. Given many generations of selective pressure, evolution can often find solutions to these kinds of problems (after all, most of us can walk and chew gum at the same time), but the hybrid mutants would have diminished use of their superpowers in the meantime, reducing any evolutionary advantage.

The “next step in evolution”

Speaking of evolutionary advantage, the concept of the X genes, and especially the nickname, “the next step in evolution,” is more in line with misconceptions about evolution than with the reality. Evolution is aimless, sloppy, and settles on compromises infinitely more often than it develops innovation. There is no directionality to evolution whatsoever and, since the environment is always changing also, most species are doing all they can to simply avoid extinction. Too often, “evolution” is equated with increases in function, complexity, and creativity, but the opposite is more often true: evolution can lead a species toward efficiency and simplicity.

Sure, us “big” species, like humans, whales, and redwoods, get all the attention, but the vast majority of living things on this planet are the single-celled prokaryotes, bacteria and archaea. If any creature should be considered the “pinnacles of evolution,” shouldn’t it be them? They have successfully mastered every conceivable niche on our planet, from pressurized scalding water, to the dark depths many miles below the planet’s surface. They are, by far, the majority of the individuals on the planet and they outnumber us even on our bodies: prokaryotic cells outnumber human cells in the human body, possibly two-to-one!

The final word on the evolutionary biology of the X-men mutants involves their reproductive success. Even if the almost infinite number of required mutations could theoretically reshape their bodies and brains as needed, and even if all of this happened in a single individual, and even if the sperm or eggs were altered as well so that the changes were made heritable, we still have a problem. Evolutionary innovation requires that the bearer of the innovation pass the gene down to descendants that outcompete, that is, out-reproduce those that have less favorable combinations of traits. Successful reproduction is the key. In addition to the enviable superhuman abilities of our mutant X-men, many of them have another quirk that we can’t ignore: many of them are anti-social.

The X-men that keep to themselves and shun romantic contact effectively take themselves out of the gene pool. This means that the mutations that seem so clearly beneficial have a fatal flaw: they also make them unlikely or unable to reproduce. On the other hand, some X-men appear to be quite fecund. Wolverine and Magneto have the most offspring, with dozens of children each (though many are in alternate timelines). Over future generations, their unique combinations of mutations will successfully enter the gene pool. If their offspring are similarly prolific, these traits have a real chance of spreading through the human population in future generations.

But for the majority of X-men, it seems that all of those wondrous mutant abilities will simply die with those that bear them. Even if the X-men themselves are immortal – because hey, anything is apparently possible – their mutations still won’t spread to the population at large. This is not adaptation; it is maladaptation. Any creature that does not reproduce is considered an evolutionary dead-end.

So much for being the next step in evolution.

[This essay first appeared in AiPT!.]



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