Since their debut in 1963, the X-Men have sworn to protect a world that hates and fears them, but here at AiPT! we’ve got nothing but love for Marvel’s mighty mutants! To celebrate the long-awaited return of Uncanny X-Men, AiPT! brings you UNCANNY X-MONTH: 30 days of original X-Men content. Hope you survive the experience…AiPT! Science is going all-in for Uncanny X-Month, with the most detailed look at X-Men biology anywhere, EVER. Kicking things off is evolutionary biologist Nathan H. Lents, on just what the heck “next step in human evolution” might actually mean.
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 genetic code.
Stan Lee, Jack Kirby, and the other Marvel creators “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, all month long.
What are mutations?
But first, a word about mutations. Lee was definitely onto 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.
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’re 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 Bolivar Trask really released mutant-detecting Sentinels into the world, they’d be going off constantly.
In the case of the X-Men, the mutations in question are those that unlock the function of previously dormant X-Gene. This, too, is based on a real biological phenomenon. Mutations that activate or deactivate a previous mutation are called spontaneous revertants and 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 via hemoglobin, a technique that may help treat a variety of anemia-causing diseases. And revertants aren’t 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).
How do genes give rise to powers?
To discuss how these mutations have their dramatic “X-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. 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’s hardly ever happened, over the entire half billion years of animal evolution. Wings have evolved three separate times in vertebrates — in birds, bats, and pterosaurs — but all of these involved the reshaping of pre-existing forelimbs, not the growth of new appendages from nothing. Yet, growing entirely new structures is a hallmark of Marvel mutants.
Of course, science fiction/fantasy is not meant to be perfectly accurate in its scientific content – that’s the “fiction” part and also what makes it fun. But it’s worth pointing out one example in particular, because the misconception it comes from is so widespread. The mutant Armando Muñoz gets the nickname “Darwin” because he can adapt — biologically, no less — to any new environmental challenges that he’s faced with. 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.
Mutations occurring in the 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. It’s only mutations in the germ line – the cells that give rise to sperm and eggs – that matter in the long run. So, in real life, a “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!)
Evolution is a slow, aimless, and utterly unsatisfying process. The rules are obviously different for the X-Gene, but his ill-suited namesake would make Charles Darwin squirm, 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 “next step in evolution”
The concept of the X-Gene, and especially mutants’ nickname, “the next step in human evolution,” is more in line with misconceptions about evolution than with the reality. Evolution is 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.
We also have to take a look at the X-Men’s 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: they’re anti-social. The mutants that keep to themselves and shun romantic contact effectively take themselves out of the gene pool. This means the mutations that seem so clearly beneficial have a fatal flaw — making them unlikely or unable to reproduce.
On the other hand, some X-men appear to be quite fecund. Wolverine and Magneto are among those with 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 who bear them. Even if the X-Men themselves were immortal, their mutations still wouldn’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 human evolution.