The Science Behind Spider-Man: Reign‘s Infamous Radioactive Semen

Marvel Comics courted controversy in the world of Spider-Man this year (not the for the first time, and almost certainly not the last) with the news that it was going to return to the infamous alt-universe tale Spider-Man: Reign in a new series from original creator Kaare Andrews. In a comics history as long as Peter Parker’s, there’s been plenty of controversial storylines over the decades, but it’s not every day you have a Spider-Man comic that includes a plotline where Mary Jane Watson dies of cancer after years of radioactive sex with Peter. But aside from the very good question of “Why did I just have to read that sentence?” fans have long asked: is that actually feasible, even beyond a world of superheroes?

Thankfully, someone is here at last to answer. Releasing this week from Smart Pop, Diana McCallum‘s Sex Lives of Superheroes: Wolverine’s Immortal Sperm, Superman’s Porn Career, the Thing’s Thing, and Other Super-Sexual Matters Explained explores the sexual reality of superhero comics in a series of speculative, informative, and frequently comedic essays to answer the questions too lewd for the pages of Marvel and DC.

Ever wondered what Steve Rogers’ sex ed would’ve been like before he became Captain America? What happened that one time Superman made a porno? Just how do healing factors like Wolverine’s and Deadpool’s factor into their sperm? All these, and more, are answered—and to celebrate its release (hi-o!), io9 is… proud, to present, McCallum’s full essay from Sex Lives of Superheroes tackling the thorny questions raised by Spider-Man Reign below.


© Smart Pop

Spider-Man, Spider-Man, Radioactive Spider-Man. Spider blood, spider blood, radioactive spider blood (repeat three times).

—From “Spider-Man: The Animated Series Theme Song” by Joe Perry

Spider-Man might just be the most popular superhero of all time, and with great popularity comes great moments in superhero (and cinematic) history. Moments like the upside-down kiss with Mary Jane in the rain, the multiple Spider-Man team-up in Spider-Man: No Way Home, and Miles Morales’s leap of faith from Into the Spider-Verse. But a hero’s life can’t be all highs, and no hero has experienced more lows than Peter Parker, a man whose origin story involves the death of his uncle, whose first love interest was killed by the recoil from his own webbing, and who had to make everyone he ever met forget he existed in order to save the world. Eep. When you think about everything Peter’s been through, it’s incredible that this guy is still so upbeat and full of puns—and we haven’t even touched on what might be Spidey’s most infamous moment, that time Peter Parker killed his wife with his radioactive semen.

What’s that, you want to learn more about that last part? That’s genuinely shocking, but sure, let’s talk about Spider-Man’s deadly splooge.

The Infamous Semen Comic

If you somehow aren’t familiar with this absolutely wild sequence of events, the previously mentioned spermicide (a homicide caused by sperm, obviously) occurred in the 2006 miniseries Spider-Man: Reign, an officially sanctioned Marvel comic. In this story we are introduced to a geriatric Peter Parker living alone in New York, having retired from being the friendly neighborhood Spider-Man after the death of his wife Mary Jane Watson-Parker years earlier. How did she die? Well, this is how Peter explained it (while clutching her decaying, unearthed corpse, if you’re curious):

The doctors didn’t understand how it happened! How you had been poisoned with radioactivity! How your body slowly became riddled with cancer! I did. I was . . . I am filled with radioactive blood. And not just blood. Every fluid. Touching me . . . loving me . . . loving me killed you! Like a spider crawling up inside your body and laying a thousand eggs of cancer . . . I killed you.

So there you have it, straight from the spider’s mouth. According to Peter (who, I’ll remind you, is a goddamn scientist), Mary Jane died from cancer caused by radioactive fluids exchanged when a couple touches and loves each other. So . . . semen. He’s saying he killed Mary Jane by infecting her with radioactive semen whenever they made love. Which feels like a wild claim to jump to without proof. For a man who constantly brings up his “radioactive spider blood” in conversation, he seems pretty certain that his semen, and not his blood or some other bodily fluid, was what caused the multiple cancers that claimed Mary Jane’s body. And while it’s well known that exposure to radiation can cause cancer, so can a lot of other things, like smoking, sun exposure, or just a poor diet. Heck, maybe Mary Jane lived near some power lines or something. Knowing Peter’s self-deprecating nature, though, it makes sense for him to automatically blame his radioactive bodily fluids for his wife’s demise, and maybe he just assumes it was his semen because that’s the only bodily fluid he knows for sure made contact with her body via unprotected sex. Or maybe he knows something we don’t.

This leads us to a few questions that need answering. One, why would Marvel publish any of that? And two, is it actually possible that Peter killed his wife with his radioactive spider-semen?

We’ll never know the answer to question one, but we can answer question two with shocking accuracy.

With Great Power Comes Great Radioactivity

The first thing we have to talk about when it comes to solving this spermicide is good old terrifying radiation itself. We know that Spider-Man is radioactive, not just because it’s brought up in all his theme songs, but because it’s the backbone of his origin story. While going about his business one day, Peter Parker was bitten by a spider that gave him spider-like superpowers (and thankfully for his social life, not a spider-like appearance). For most people a spider bite just gives you an annoying bump on your skin, but the spider that bit Peter had been exposed to high levels of radiation and caused what’s known as internal radiation contamination (and also caused him to develop superpowers that kept that radiation from killing him, unlike poor Mary Jane). According to the Centers for Disease Control and Prevention (CDC), internal contamination occurs “when radioactive materials enter the body through an open wound or are absorbed through the skin” and a spider bite definitely qualifies as an open wound (as opposed to “external contamination,” which is when radioactive material comes into brief topical contact with a person’s skin, hair, or clothing). But the CDC also backs up Peter’s claim that his bodily fluids would be radioactive enough to contaminate others. 

People who are internally contaminated can expose people near them to radiation from the radioactive material inside their bodies. The body fluids (blood, sweat, urine) of an internally contaminated person can contain radioactive materials. Coming in contact with these body fluids can result in contamination and/or exposure.

Now, you might notice the researchers at the CDC did not specifically mention semen as one of the bodily fluids that can expose someone to radiation, but don’t worry, braver scientists than them assure us later in this chapter that semen is also brimming with radiation in a person who has been internally contaminated.

So, we’ve established that Peter’s semen is in fact radioactive, but so are all the other fluids in his body. To prove it was indeed his semen that killed Mary Jane, we need to know how much radiation semen holds compared to other bodily fluids. And to do that we’re going to have to explore some weird places with our good friend science or you won’t even believe the answer when we get there. 

To prove Peter’s radioactive Semen-Man theory, we need to know what type of radiation he was infected with back when he was a skinny little nerd. Unfortunately, no comic or movie has ever provided us with the exact type of radiation the spider that bit Peter was irradiated with; we’re just told it was generally radioactive. We have places to be and semen to discuss, so we can’t run through every radioactive element in existence right now, but there are a few deadly and well-documented suspects we can consider. For example, in 2006 a former Russian spy named Alexander Litvinenko died several weeks after his tea was poisoned with the radioactive element polonium-210. After he was diagnosed with radiation poisoning, the British government shut down several restaurants and nightclubs Litvinenko had recently visited in case he had excreted significant amounts of polonium as he went about his day. This means scientists and governments agree that radiation exposure through bodily fluids is something to be concerned about with this element. However, polonium is not likely to be what Peter was infected with, as this stuff is so potent that it kills in about a week and is not commonly associated with cancer, which is what killed Mary Jane.

It’s much more likely that the spider that bit Peter was exposed to something like uranium, which is what we’ll assume from this point on. Uranium is a radioactive element that can exist in the body for long periods of time without killing the infected person (as we’re about to learn) but is also known to cause lethal instances of cancer over long periods of exposure. In fact, a 2015 study found that uranium miners had a 32 percent chance of dying from cancer,11 which is double the global cancer mortality rate of 16 percent. So uranium exposure could definitely explain MJ contracting multiple cancers that formed over several years in Spider-Man: Reign. As a bonus for our purposes, scientists have been studying the effects of uranium on bodily fluids for some time now, so strap in for what is hopefully the only roller-coaster ride you will ever go on that includes radioactive blood, urine, and semen.

Spider Man Reign Radioactive Sperm Marvel
© Kaare Andrews/Marvel Comics

Which Bodily Fluid Killed Mary Jane?

For the information we’re about to explore, we must thank the U.S. Department of Veterans Affairs (USDVA) and their study titled Semen Uranium Concentrations in Depleted Uranium Exposed Gulf War Veterans: Correlations with Other Body Fluid Matrices. What this long title boils down to is that in 2009 a group of scientists worked with thirty-five veterans of the Gulf War to study the effects of long-term exposure to uranium, which specifically included checking the uranium levels in their blood, urine, and semen. And for that, we salute them.

The participants in this study were all exposed to uranium during the Gulf War in 1991, but their bodily fluid samples were taken in 2009, eighteen years after exposure—and wouldn’t you know it, after all that time, all of their bodily fluids still contained radioactive uranium elements. This is

relevant because Peter was with Mary Jane for at least a decade in the comic before she started getting sick from radiation poisoning, so we can safely assume Peter was still excreting significant amounts of radiation from all of his bodily fluids ten years into their relationship. This also means he was unknowingly being the menace J. Jonah Jameson claimed he was for all those years.

So Peter was right that “every fluid” in his body was likely still radioactive years after his famous spider bite. Now, let’s get to the main event and talk about splooge. The researchers of the aforementioned study created a scale of what they expected the uranium levels in the semen of their subjects to be, which ranged from low (5 picograms/gram) to medium (50 pg/g) to high (1,000 pg/g). What they ended up finding was that half the participants had uranium levels that were considered high and above. One participant even had a uranium count in their semen of 3,350 pg/g, which is more than three times the “high” mark they expected. So not only were their subjects still excreting uranium eighteen years after exposure, they were releasing significantly more than predicted.

That makes semen a prime suspect in the killing of Mary Jane. But to determine once and for all that Peter’s semen was indeed responsible for this deadly spermicide (so we can, I don’t know, send him to sperm jail or something), we need to know for certain which bodily fluid holds the most radiation. So next we’ll look at exactly how much uranium was found in equivalent amounts of each bodily fluid, including blood, urine, sweat, and semen. (The USDVA study didn’t actually include an analysis of the uranium levels found in sweat. Fortunately, they aren’t the only bodily fluid game in town. A different study from the University of Alberta tells us that, on average, sweat will contain ten times as much uranium as urine, so we’ll use that estimate in our calculations for sweat.) With that in mind, here are the average amounts of uranium found in the participants of the USDVA study, sorted by bodily fluid:

Blood: 0.16 pg/g

Urine: 5.39 pg/g

Sweat: 53.9 pg/g (estimated)

Semen: 306.91 pg/g

Holy web shooters, semen is bursting with radiation compared to other bodily fluids. These numbers tell us that semen has about six times more radiation than sweat, fifty-seven times more radiation than urine, and almost two thousand times more radiation than blood! At that rate it’s a wonder that Peter’s testicles aren’t emitting a soft radioactive glow to warn women away from his deadly little swimmers or setting off his own spider sense every time he goes near his genitals. All the evidence so far is certainly pointing to spider-semen as the killer, but the final question is whether Mary Jane was exposed to enough uranium from Peter’s web fluids to make her sick. According to the CDC, “in order for uranium inside the body to cause cancer, the levels of uranium have to be so large that they are easily detected by laboratory analysis.” Since scientists detected these radioactive bad boys pretty easily and found that the levels were literally higher than high, we can safely slap the handcuffs on semen as being the bodily fluid that struck Mary Jane down. Talk about a neogenic nightmare, and a twist on the accepted lore.

The Spider-Man mythos is consistently hung up on Peter’s “radioactive spider blood,” but looking at these numbers, the amount of radiation in his blood is frankly negligible compared to his semen and other bodily fluids. We’re going to have to do some controversial rewrites of a few Spider-Man theme songs for accuracy is all I’m saying. But before that, we might owe Spider-Man: Reign an apology for dismissing their autopsy results, as Peter turned out to be right—his radioactive semen definitely killed his wife. And it’s safe to say no one saw that coming. Considering how dangerous it is to be married to Spider-Man, deadly sperm was a pretty low contender on the list of things that might kill MJ. Personally, I had money on the Kingpin.

While killing your wife is one potential side effect of having radioactive spider-semen, unfortunately it’s not the only one. We also have to consider what effect this deadly load may have on the couple’s ability to conceive a child and how it may impact said child. But let me just say before we dive into the results, it’s not nearly as bad as killing your wife (though not many things are).

The Itsy-Bitsy Spider Baby

Most people know that high doses of radiation exposure to the testes or ovaries can lead to temporary or permanent sterility, but it turns out that radiation has shockingly little effect on the sperm or eggs when it comes to things like birth defects, miscarriage, or mutation. While it’s possible that Peter’s radioactive fluids would make it difficult for him and MJ to conceive at all, if they do manage to get pregnant, the risk of their child having birth defects or mutations is shockingly low. Everything you’ve ever seen or read about exposure to radiation may tell you that this can’t possibly be right, as you may be picturing the radioactive three-eyed fish from The Simpsons right now or pointing out that Peter Parker himself mutated into a spider man from a radioactive spider bite, but in real life it turns out that eggs and sperm are not as easily mutated as comic books would lead us to believe.

An extensive study on the effects of radiation exposure from the Chernobyl nuclear power plant disaster in 1986 looked at the genetics of the children of two hundred survivors of the incident and found there were no mutations in the survivors’ children. None! Scientists concluded that radiation could absolutely cause DNA damage and increase the risk of cancer to those directly exposed to it, but found that the number of germline mutations (a mutation passed on from parents to offspring) was no greater in the children of highly exposed parents than those of children born to parents who were not exposed at all. So basically, radiation can change your own DNA, but not the DNA you pass on to your children. What does this mean for a potential friendly neighborhood spider-baby? Well, if Peter and Mary Jane did have children, they would likely have no radiation-related mutations, which means Baby Parker-Watson wouldn’t inherit any of Peter’s spider-powers and would just be a regular baby. That baby would still be a menace in the way that all babies are, but less of a menace than one with super strength and the ability to shoot webs out of its wrists.

Using Protection in the Bedroom

We know now that it was indeed Peter’s semen that killed Mary Jane, but let’s explore a little further and figure out if there was any way he could have protected her from his little radioactive relatives. After all, he wouldn’t be the first superhero who had to figure out how to safely have sex with their partner because their powers were on the murderous side. Rogue and Gambit of the X-Men have been an on-again, off-again couple for decades, partly because of their genuine relationship issues and partly because if Rogue’s skin comes into contact with Gambit it would literally suck the life out of his body, which is both a mood killer and a killer-killer. The couple have only managed to be intimate a handful of times when Rogue’s powers have been dampened by one plot device or another, but most of the time they must simply keep a physical distance for safety’s sake and refrain from touching each other. So, an abstinence-based approach with no sexual-thwipping of any kind is one option to protect Mary Jane, but Peter might be happier emulating DC power couple Harley Quinn and Poison Ivy, who managed to overcome a similar sexual conundrum as our friendly neighborhood Spider-Man. As her name suggests, Poison Ivy is, well, poisonous. She’s capable of secreting toxic substances from her body, including the ability to kill with a poison kiss, which is useful when you’re trying to murder horny billionaires but annoying when you’re trying to make out with your girlfriend. A death kiss would definitely be a safety concern in the bedroom, but Poison Ivy is also a scientist and used her most beautiful body part (her brain!) to create a vaccine to inoculate Harley against Ivy’s more poisonous traits. This antitoxin allows the couple to safely be intimate and includes the fun side effect of giving Harley increased strength and stamina, which is something that will never go astray in the bedroom. Heck, maybe Ivy just threw those powers in there because she thought it’d be fun. Respect, if so. Either way, her workaround shows that it’s possible for a potentially toxic couple to use creative forms of protection to practice safe sex, and Peter had several very good options to choose from to protect Mary Jane if he had known his downstairs web fluid was dangerously irradiated.

As discussed, Peter was contaminated with radiation internally, which means he is not emitting waves of radiation outside his body, and the only way he can contaminate another individual is through physical contact with his bodily fluids. Since Mary Jane died from direct semen exposure, we can deduce that the couple regularly had either oral or penetrative sex without using a condom, which has to be the weirdest way to ever verify a superhero is rawdogging it with his wife. A great way for Peter and Mary Jane to stop this exposure from happening is to just use condoms during sex—this would have kept her from coming into contact with his semen, which we now know was the leading cause of her cancer. Using condoms wouldn’t have stopped her from coming into contact with Peter’s sweat during sex, but this would be far less of a concern considering that sweat contains five times less radiation than semen and also that very minimal amounts would go inside MJ’s body. Considering his spider-strength and stamina, it seems doubtful sex is even an intense enough activity to make Peter start sweating in the first place. And even if he was sweating up a storm, condoms definitely wouldn’t have hurt as an added precaution.

But condoms aren’t the only protection Peter could have used; there are also a few radiation treatments that can be administered after exposure. As mentioned earlier, we can only guess at the exact type of radiation that Peter was exposed to by his spider bite, but if he happened to be infected with, say, radioactive iodine instead of uranium, Mary Jane could have taken potassium iodide pills after sex to counteract the effects, kind of like a morning-after pill but for radiation exposure. The CDC warns that to be effective “a person must take [potassium iodide] before or shortly after exposure to radioactive iodine,” though, so she’d have to be quick.

Similarly, if Peter’s body excretes cesium or thallium then Mary Jane could be treated with a pill called Prussian blue, which prevents the body from absorbing the radioactive material. This pill can save your life but will also turn your mouth, teeth, and stool blue, so Mary Jane would be alive but would look like the girl who turned into a blueberry at Willy Wonka’s chocolate factory. Finally, if Peter was radiated with plutonium, americium, or curium, a more extreme treatment called DTPA (diethylenetriamine pentaacetate) could help treat any resulting infection MJ incurs. This treatment must be taken either through an IV or as a mist that is breathed into the lungs, and it would have to be administered each time they had sex, which would certainly bring a whole new meaning to “playing doctor” in the bedroom. So, Mary Jane definitely has some treatment options for radiation exposure, but when all is said and done, the easiest and safest method is for Peter to just wear a condom, which you wouldn’t think would be difficult for a guy who wears a full-body spandex suit as part of his day job.

Much like Peter Parker, we need to wrap things up, but let’s close out this chapter by exploring how the radioactive revelations we’ve uncovered might affect the rest of the superhero world.

Other Radioactive Heroes Waiting to Kill

Unfortunately for all the potential human sexual partners in the Marvel universe, Peter Parker is not the only superhero out there who may be waiting to kill via repeated radioactive orgasms (or even just one).

Other famously radioactive heroes include the Fantastic Four, who obtained their powers by being bombarded with cosmic radiation. Luckily for team members Reed Richards and Sue Storm, the risk of infecting a lover with radiation during sex is of little concern as they are happily married to each other and have no other sexual partners. Plus, since they got their powers from the same source of radiation, it seems pretty unlikely their bodily fluids could hurt each other. Ben Grimm similarly doesn’t have much concern in this department, as we will discuss in a later chapter how he likely has no penis with which to ejaculate, therefore eliminating the risk of this particular contaminant. That just leaves Johnny Storm, aka the Human Torch, a known playboy who has dated dozens of women over the years, which could be good or bad in this scenario. It’s definitely bad that he’s possibly poisoned dozens of women with radioactive semen when he “flames on” during intercourse, but the fact that he doesn’t date women for a particularly long time also makes it less likely that he’s exposed any one partner to a particularly dangerous amount of radiation. After all, we’re told that Peter’s deadly semen slowly killed Mary Jane over many years, so Johnny’s fear of commitment may have saved the lives of many of the women he’s dated. What a hero. Also, judging by the lack of little Johnnys running around the Marvel universe, it seems likely that Johnny wears a condom when he has sex, which might be the only example we have of Johnny Storm displaying a sense of responsibility.

Of course, we can’t discuss radioactive superheroes without mentioning the gamma-radiated green rage-monster, the Hulk, aka Bruce Banner. In the previous chapter we discussed the danger of Bruce potentially hulking out whenever he orgasms, but an even better reason for him to abstain from carnal pleasures is the fact that his semen is likely powerful enough to kill on contact. Remember, Peter got his powers from a small spider bite, and that was enough radiation to kill his wife after a few years of exposure, but Bruce got his powers from standing directly in the blast radius of a gamma bomb. We already know that Bruce’s blood contains enough radiation to kill someone—in The Incredible Hulk movie a man accidentally ingests a small drop of Bruce’s blood mixed into a soda and immediately falls unconscious from “gamma sickness.” If Bruce’s semen is like Peter’s and contains two thousand times more radiation than his blood, well, I’m not even going to bother with any fun math in this instance, I’m just going to say that’s too much radioactive semen for any human to handle. We’re talking about a substance so toxic it would melt a person in half immediately upon exposure. So, for everyone’s safety, don’t make Bruce horny; you wouldn’t like him when he’s horny.

As for Peter Parker, well, it seems he has another tragedy to spur on his superhero exploits as he is now indirectly responsible for the death of both his uncle and his wife. But maybe a lesson can be learned here, which is that being a hero means protecting people. And protecting people can be as simple as putting on a spandex supersuit—or putting on a condom.


Sex Lives of Superheroes: Wolverine’s Immortal Sperm, Superman’s Porn Career, the Thing’s Thing, and Other Super-Sexual Matters Explained is available to purchase now.

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