Melanin, aggression, and sexuality

I began researching melanin and its effects based on rumors that injecting it into animals makes them more aggressive. The search, so far, has led me down even weirder rabbit holes than usual.

Why do people tan? Not physically, but cosmetically. Cosmetic tanning is probably unhealthy (skin cancer,) costs money if you use a tanning salon, historically novel, and boring as fuck.

Tanning is especially confusing if you take the ideas of Critical Theory/White Privilege seriously, because then why would anyone want to look ethnically darker than they actually are? Are millions of whites unconsciously trying to pull a Doleazal?

But women do not pair their tans with darker hair; they pair their tans with lighter hair. The result, I suppose, is like a dark-skinned German. It makes about as much sense to me as ganguro girls.


The obvious answer is that women tan because it gets them sexual interest from men, which is the answer to virtually every question along these lines, but this only kicks the question back a notch: why are men sexually interested in tan women? Of course, something could arise, chicken and egg, as nothing more than a signal of sexual availability that men then respond to as a signal of availability. But this is a dull hypothesis, so let’s abandon it and carry on.

First, a  quick note on what melanin is: melanin is a kind of “natural pigment” found in your brain, (eg, the substantia nigra,) skin, irises, the feathers of birds, squid ink, fungi, plants, micro-organisms, etc. There are a few different types of melanin, which cause different skin colors.

White people, btw, aren’t albino.

Overall, I find that conservative and politically moderate women tend to tan, (and bleach their hair,) while liberal women do not. I suspect that conservatives and moderates do more of almost any image-enhancing thing, perhaps because they are more often on the sexual market (conservatives have more divorces than liberals and become sexually active younger.) It’s not clear to me, though, if this is just a “thing dumb people do” rather than a specifically conservative/moderate thing.

Peter Frost suggests that melanin plays a role in visually identifying adults (and men.) Children (of all races) tend to be lighter skinned/have less melanin than adults*, like this girl from Vanuatu, whose hair is that color naturally:


Her hair will darken with age, just like many other blond children.

*I suspect this is just because adults have spent a longer total amount of time in the sun than children.

Women generally have lighter skin than men, which Frost proposes is a neotenous trait which thus:

1. Increases the male desire to provide for women, making marriage more likely

2. Decreases male aggression toward females, making marriage less likely to result in dead women

3. implies a lack of sexual experience with other men.

He suggests that the tanned appearance, therefore, implies sexual maturity; purposeful tanning or glorification of tanning, therefore, implies a desire for sexual availability rather than virginity.

In a culture where evolutionary success is determined by the stability of one’s monogamous pair-bond, people valued and cultivated traits that led to or implied that one would be a good partner. In a culture where success is determined by one’s ability to get multiple partners over one’s lifetime, traits that enhance sexual availability will be valued.

Men also tan, (often in conjunction with weightlifting,) in order to better fit the archetype of “tall, dark, and handsome” and thus get laid. On one post I found contained explicit denunciation of PUA “personality” and “conversation” techniques as just for men who want stable, long-term relationships rather than lots of one night stands with hot chicks, the body-builders’ goal. Well, that’s a new criticism.

Does more melanin actually lead to more sex? Certainly there is a correlation among humans between pigmentation levels and (reported) frequency of sex. According to Rushton’s article, “Do pigmentation and the melanocortin system modulate aggression and sexuality in humans as they do in other animals?” Ford and Beach (1951) report that Pacific Islanders and Native Americans claim to have sex 1 to 4 times per week, US Whites 2–4 times, and Africans from 3 to >10. Rushton and Bogaert (1987 and 1988) concluded, based on Kinsey data, that Blacks more sex than whites. The WHO reports that, (for married 20-somethings,) the Japanese and Chinese have sex 2.5 times per week, American whites 4 times per week, and American blacks have sex 5 times per week. Also,

“A Los Angeles study found that the age of first sexual activity in high school students was 14.4 years for Blacks, 16.4 years for East Asians, with Whites in the middle. The percentage of students who were sexually active was 32% for East Asians and 81% for Blacks, with Whites again between the other two. In another study, White Americans reported more sex guilt than Black Americans and that sex had a weakening effect. Blacks said they had casual intercourse more and felt less concern about it than Whites.”

Correlation, correlation, correlation.

Luckily (for our purposes, anyway,) there appears to be a sub-population of people actively injecting themselves with chemicals intended to increase the amount of melanin in their skin, and reporting the effects on the internet. (While some of the posts on the subject sound too similar too each other, and thus I suspect they were made by shills trying to market the drugs they’re selling, I think some of these posts are legit.)

First, a digression: Yes, there are people out there making injectible tanning drugs. No, I don’t recommend them, because everything about them comes with a big warning label that says, “THIS MIGHT CAUSE CANCER.” They haven’t been approved by the FDA, so you can’t buy them from legal sources.

Why invent a tanning drug? Aside from the obvious reasons, because there are people with vitigilio and rare skin conditions that make them super-prone to burning who could potentially use it. The drugs aren’t injectible melanin. (I haven’t seen anything about anyone injecting actual melanin.) They’re an artificially synthesized chemical similar in structure to α-Melanocyte-stimulating hormone (a-MSH,) which, as its name implies, stimulates the body to produce melanocytes, which are cells that produce melanin.

So, what happens when people inject themselves with a drug kinda like a-MSH? Well, they get tan. They get a better night’s sleep. And they get constant erections.

Apparently, the drugs are also being investigated as an alternative to Viagra.

One thing almost no one seems to be noticing is aggression. One guy did note he was feeling some anger, but everyone else responded that they’d felt nothing of the sort, so it was probably just some random thing going on with one guy. That said, I’m not convinced that people are all that good at realizing that they’ve become more aggressive–they tend to just blame their aggression on other people suddenly sucking more. I also assume that people who are getting constant erections are going to try to do something about it, which could lead to more sexually aggressive behaviors, without causing, say, random fights.

So, Melanotan II/melanin/a-MSH does seem to have some causal relationship with sex, but so far nothing shows that it increases aggression.

Some black people have noticed that whites are injecting themselves with Melanotan II to make themselves look darker and get more erections, and while some of them think this is absolutely hilarious, others take it very badly. (This is interesting, but slightly off-topic, so I will reserve these observations/comments for a later post.)

Anyway, back on subject.

Another reason people may tan is that it appears to trigger the release of endorphins, leading to speculation that some people are actually addicted to tanning:

“While many report that the desire for a tanned appearance is the strongest motivation for sunbathing and tanning bed use, tanners also report mood enhancement, relaxation, and socialization. It has been suggested by the popular media and suspected by dermatologists for years that one reason tanning is so popular is that UV light is addictive. …

“UV light has been shown to increase release of opioid- like endorphins, feel-good chemicals that relieve pain and generate feelings of well-being, potentially leading to dependency.

“A 2006 study used naltrexone, a drug that blocks the endorphins produced in the skin while tanning, to induce symptoms of withdrawal in frequent tanners. … These symptoms were not observed in any of the infrequent tanners given naltrexone in the study.

“Another study found that frequent tanners were able to distinguish between otherwise identical UV and non-UV light-emitting tanning beds. Tanners in this study showed an overwhelming preference (95 percent) to tan in the UV light-emitting bed. Participants suggested that UV tanning created a more relaxed mood and even relieved pain, possibly due to endorphin release.”

A former tanning addict writes:

“I was a tanning addict. Being brown was being me. If I wasn’t tanned, then I didn’t look like “me”. Silly I know, but that’s just the way I felt. Having a tan made me feel better about myself. I used to say it was like a “tonic” – it made me feel more confident and more healthy.”

Here’s her picture:


Tanned and bleached. But I think the ganguro girl rocked the style better.

What does the scientific literature have to say about melanin levels and aggression? Like, what happens when you inject a mouse with melanin-inducing hormones, or breed mice to have low melanin levels?

Luckily for me, Takase et al have done a meta-analysis of studies done on mice who’ve been genetically modified not to produce much melanin. “MCH” stands for Melanin-Concentrating Hormone. As far as I can tell, More MCH => More Melanin. Phrases like “MCH knockout,” “MCH deletion,” and “MCH deficiency” all refer to mice that have been modified so that they don’t make much (or any) MCH. So Less MCH => Less Melanin. (If I’ve got thi wrong, please tell me.)

From the paper:

“Overall, the meta-analysis revealed that the deletion of MCH signaling suppressed non-REM sleep, anxiety, response to novelty, startle response, stress-induced hyperthermia, conditioned place preference, and olfaction (p<0.05) and that MCH signaling deficiency enhanced locomotor activity, wakefulness, alcohol preference, motor activation by psychostimulants, aggression, male sexual behavior, and social interaction (p<0.05).”

So, in plain speak, Less Melanin => crappy sleep, anxiety, aggression, and sex.

However, I would like to caution that you are not a mouse. There are some big differences between you and mice, like that mice can synthesize vitamin C and you can’t. Also, your body has had thousands of years to adapt to your melanin levels, to keep you healthy under certain environmental conditions. MCH-deficient mice don’t have that same luxury; their bodies might just not be adapted to cope with some side effect of MCH deficiency.

So let’s keep looking.

Demas at all have an interesting article, “Adrenal hormones mediate melatonin-induced increases in aggression in male Siberian hamsters (Phodopus sungorus)

From the article:

“In Experiment 1, male Siberian hamsters received either daily (s.c.) injections of melatonin (15 Ag/day) or saline 2 h before lights out for 10 consecutive days. In Experiment 2, hamsters received adrenal demedullations (ADMEDx), whereas in Experiment 3 animals received adrenalectomies (ADx); control animals in both experiments received sham surgeries. Animals in both experiments subsequently received daily injections of melatonin or vehicle as in Experiment 1. Animals in all experiments were tested using a resident–intruder model of aggression. In Experiment 1, exogenous melatonin treatment increased aggression compared with control hamsters. In Experiment 2, ADMEDx had no effect on melatonin-induced aggression. In Experiment 3, the melatonin-induced increase in aggression was significantly attenuated by ADx. Collectively, the results of the present study demonstrate that short day-like patterns of melatonin increase aggression in male Siberian hamsters and suggest that increased aggression is due, in part, to changes in adrenocortical steroids.”

“Several studies have demonstrated photoperiodic changes in aggression in both male and female rodents (Badura and Nunez, 1989; Fleming et al., 1988; Garrett and Campbell, 1980; Jasnow et al., 2000). For example, male Syrian hamsters (Mesocricetus auratus) maintained in short days for 8 weeks undergo gonadal regression and display increases in aggression compared with long-day hamsters, despite basal serum concentrations of testosterone (T) (Garrett and Campbell, 1980). Interestingly, prolonged maintenance (i.e., N15 weeks) in short days triggers gonadal recrudescence and the short-day increases in aggressive behavior largely disappear, returning to long-day levels of aggression by 21 weeks…”

(I think “gonadal regression” means the gonads got smaller, which would imply less sexual activity.)

“…both pinealectomy and treatment with exogenous melatonin within species-typical physiological ranges also affect aggression in photoperiodic species. For example, pinealectomy eliminates the short-day increase in aggression in female Syrian hamsters, whereas exogenous melatonin treatment augments aggression in long-day-housed animals (Fleming et al., 1988). Short-term treatment with exogenous melatonin also increases aggression in male Syrian hamsters without altering serum T concentrations (Jasnow et al., 2002).”

Now we’re getting somewhere, right? Except, wait, that’s MELATONIN, not melanin. Different chemical. Melatonin is a chemical your brain makes (in your pineal gland) in response to darkness/dim light helps you fall asleep and helps keep your circadian rhythms functioning properly. Increasing melatonin appears to decrease melanin–“As early as 1917, Carey Pratt McCord and Floyd P. Allen discovered that feeding extract of the pineal glands of cows lightened tadpole skin by contracting the dark epidermal melanophores.” (from the Wikipedia.) This makes sense: Longer days => less darkness => less melatonin => more melanin so you don’t burn in the sun. Shorter days => more darkness => more melatonin => less melanin so you can absorb more of the limited sunlight.

But I suspect that here we have found the source of the original rumor: Someone read a study about melatonin, which makes hamsters cranky and aggressive, and confused it with melanin, which appears to make mice less aggressive.

But wait. Aren’t hamsters (and other rodents) nocturnal? Whereas humans generally aren’t?

Yup. So hamsters and mice might actually be designed to be more active when they have more melatonin, and humans might be designed to be less active.

Luckily for us, humans regularly consume supplemental melatonin. According to eHealthMe, “2,237 people reported to have side effects when taking Melatonin. Among them, 32 people (1.43%) have Aggression.”

Honestly, 1.43% is nothing; that’s more like statistical noise in your data.

Some parents who’ve put their autistic kids on melatonin report aggression or aggression-like symptoms:

“…tonight he was grabbing his face and squeezing it(which he has never done before) and just kept crying then fell asleep about ten minutes later???”

“I have used Melatonin to help my Autistic son sleep but when I do he gets very aggressive and knocks things over and lashes out. I actually have to hold him down or wrap my legs and arms around him from behind or he will try and head butt you until he settles and this behavior repeats for a couple of days till the Melatonin leaves his system and then he is mellow again, for takes 72 hours to leave his system. This behavior manifests itself only when I gave him melatonin.”

But other people report the opposite:

” …good things with the Melatonin. It has been a few weeks and aggression is still significantly down as is the stimming.”

“I Started Taking Nightrest With Melatonin And Ive Gotten Much Deeper Nights Sleep. My Work Outs Got Better, Recovery Was Way Better And Aggression Level Decreased…”

Some of the moms suggest that what’s actually happening when the autistic kids become “aggressive” is that they are experiencing some form of night terrors/waking dreams, since melatonin makes people have more/deeper REM sleep, (I think that’s accurate,) rather than actual aggression.

One wonders if scientists could tell the difference between a sleep-walking hamster and a regular one!

Well, shit, this isn’t looking good for any interesting theories. I might end up with a boring result: nothing.

But let’s take a quick look at sexuality. Does summer correlate with conception? I took the birth month data from Live Science, divided by number of days per month and subtracted average gestation length to get the number of conceptions per day:

April: 11k per day

May: 11k per day

June: 11.5k per day

July: 11k per day

August: 11.5k per day

September: 12k per day

October: 12k per day

November: 12.5k per day

December: 12.5k per day

January: 12k per day

February: 12k per day

March: 11.5k per day

So, conceptions per month increase from July through December–that is, as the days get shorter and melatonin increases. Conceptions decrease from Jan through May–as the days get longer and melatonin decreases. This conception schedule is also consistent with the traditional availability of food in the northern hemisphere, with the harvest beginning in July and still enjoyed in December, but the supply dwindling as winter and then spring commence. (On the other hand, LiveStrong claims, ” high levels of melatonin may have a contraceptive effect on those hoping to conceive. Men using the supplement may notice a decrease in sperm count, decreased sperm mobility and increased breast size. Both men and women may experience a decrease in sex drive.” but doesn’t offer a source. The University of Maryland Medical Center says something similar, though, and they seem fairly trustworthy.)

Since rodent gestation lengths and human ones are radically different, I’m not going to bother looking up when mice have babies.

That violent crime (and even political revolutions) goes up in the summer is well-documented, but most theories attribute this to people getting out more or heat making them cranky.


No one seems to be injecting melanin, but synthetic versions of melanin-producing hormones do seem to make people horny and tanning releases happy hormones. No one is reporting increased aggression as a result of increased melanin.

Mice who’ve been bred not to produce melanin are more aggressive than mice who haven’t.

Injecting hamsters with melatonin makes them aggressive. Melatonin isn’t melanin, but it sounds similar. Increasing melatonin appears to decrease melanin.

Melatonin supplements don’t really seem to make humans more aggressive. There are some claims that melatonin decreases libido.

Humans do conceive more babies in fall (when melatonin levels are rising) than in spring (when they are falling) and commit more crime in the summer (when melanin is up) than in winter (when it’s down.)

Conclusion: Someone probably mixed up melanin and melatonin.


10 thoughts on “Melanin, aggression, and sexuality

  1. This article goes a lot of places, but misses some points that are quite obvious. A tan makes people of all races look healthier. Possibly because it can have a similar effect to eating a lot of carotenoid-rich vegetables (which gives a warm golden tone to the skin) suggesting a healthy diet, and also possibly because in the past everyone was out in the sun, so if you didn’t have tan skin, it suggested there was something wrong. As for liberals not tanning as much, it may just be that liberals tend to be more health-conscious. (In which case I’d like to mention that daily mild-moderate sun exposure does not carry the same risks as tanning in a bed, and is likely actually beneficial.)


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