Saturday, October 11, 2014

Yes, demons do exist

Chlamydia infection rate, by country (WHO 2004, Wikicommons). Sub-Saharan Africa has been a natural laboratory for the evolution of sexually transmitted pathogens, including strains that can manipulate their hosts.


Are we being manipulated by microbes? The idea is not so whacky. We know that a wide range of microscopic parasites have evolved the ability to manipulate their hosts, even to the point of making the host behave in strange ways. A well-known example is Toxoplasma gondii, a protozoan whose life cycle begins inside a cat. After being excreted in the cat's feces, it is picked up by a mouse and enters the new host's brain, where it neutralizes the fear response to the smell of cat urine. The mouse lets itself be eaten by a cat, and the protozoan returns to a cat's gut—the only place where it can reproduce (Flegr, 2013).

T. gondii can also infect us and alter our behavior. Infected individuals have longer reaction times, higher testosterone levels, and a greater risk of developing severe forms of schizophrenia (Flegr, 2013). But there is no reason to believe that T. gondii is the only such parasite we need to worry about. We study it in humans simply because we already know what it does in a non-human species.

Researchers are starting to look at manipulation by another human parasite, a sexually transmitted bacterium called Chlamydia trachomatis. Zhong et al. (2011) have found that it synthesizes proteins that manipulate the signalling pathways of its human host. These proteins seem to facilitate reinfection, although there may be other effects:

Despite the significant progresses made in the past decade, the precise mechanisms on what and how chlamydia-secreted proteins interact with host cells remain largely unknown, and will therefore still represent major research directions of the chlamydial field in the foreseeable future. (Zhong et al., 2011)

What else would a sexually transmitted pathogen do to its host? For one thing, it could cause infertility: 

While several nonsexually transmitted infections can also cause infertility (e.g., schistosomiasis, tuberculosis, leprosy), these infections are typically associated with high overall virulence. In contrast, STIs tend to cause little mortality and morbidity; thus, the effect on fertility seems to be more "targeted" and specific. In addition, several STI pathogens are also associated with an increased risk of miscarriage and infant mortality (Apari et al., 2014)

Chlamydia is a major cause of infertility, and this effect seems to be no accident. Its outer membrane contains a heat shock protein that induces cell death (apoptosis) in placenta cells that are vital for normal fetal development. The same protein exists in other bacteria but is located within the cytoplasm, where it can less easily affect the host's tissues. Furthermore, via this protein, Chlamydia triggers an autoimmune response that can damage the fallopian tubes and induce abortion. This response is not triggered by the common bacterium Escherichia coli. Finally, Chlamydia selectively up-regulates the expression of this protein while down-regulating the expression of most other proteins (Apari et al., 2014).

But how would infertility benefit Chlamydia and other sexually transmitted pathogens? Apari et al. (2011) argue that infertility causes the host and her partner to break up and seek new partners, thus multiplying the opportunities for the pathogen to spread to other hosts. A barren woman may pair up with a succession of partners in a desperate attempt to prove her fertility and, eventually, turn to prostitution as a means to support herself (Caldwell et al., 1989). This is not a minor phenomenon. STI-induced infertility has exceeded 40% in parts of sub-Saharan Africa (Apari et al., 2011).

It gets kinkier and kinkier

Does the manipulation stop there? We know, for instance, that sexual promiscuity correlates with the risk of contracting different STIs, but is this a simple relationship of cause and effect? Could an STI actually promote infidelity by stimulating sexual fantasizing about people other than one's current partner?

Let's look at another pathogen, Candida albicans, commonly known as vaginal yeast, which can cause an itchy rash called vulvovaginal candidiasis (VVC). Reed et al. (2003) found no significant association between VVC and the woman's frequency of vaginal sex, lifetime number of partners, or duration of current relationship. Nor was there any association with presence of C. albicans in her male partner. But there were significant associations with the woman masturbating or practicing cunnilingus in the past month.

VVC is thus more strongly associated with increased sexual fantasizing, as indicated by masturbation rate, than with a higher frequency of vaginal intercourse. This does look like host manipulation, although one might wonder why it doesn't translate into more sex with other men, this being presumably what the pathogen wants. Perhaps the development of masturbation as a lifestyle (through use of vibrators and pornography) is making this outcome harder to achieve.

A sexually transmitted pathogen can also increase its chances of transmission by disrupting mate guarding. This is the tendency of one mate, usually the male, to keep watch over the other mate. If mate guarding can be disabled or, better yet, reversed, the pathogen can spread more easily to other hosts. This kind of host manipulation has been shown in a non-human species (Mormann, 2010).

Do we see reversal of mate guarding in humans? Yes, it's called cuckold envy—the desire to see another man have sex with your wife—and it's become a common fetish. Yet it seems relatively recent. Greco-Roman texts don't mention it, despite abundant references to other forms of alternate sexual behavior, e.g., pedophilia, cunnilingus, fellatio, bestiality, etc. The earliest mentions appear in 17th century England (Kuchar, 2011, pp. 18-19). This was when England was opening up to world trade and, in particular, to the West African slave trade.

Sub-Saharan Africa has been especially conducive to sexually transmitted pathogens evolving a capacity for host manipulation. Polygyny rates are high, in the range of 20 to 40% of all adult males, and the polygynous male is typically an older man who cannot sexually satisfy all of his wives. There is thus an inevitable tendency toward multi-partner sex by both men and women, which sexually transmitted pathogens can exploit ... and manipulate.

What about sexual orientation?

A pathogen can also become more transmissible by giving its host a new sexual orientation. This strategy would disrupt the existing pair bond while opening up modes of transmission that may be more efficient than the penis/vagina one. Some vaginal strains of Candida albicans have adapted to oral sex by becoming better at adhering to saliva-coated surfaces (Schmid et al., 1995). Certain species that cause bacterial vaginosis, notably Gardnerella vaginalis and Prevotella, seem to specialize in female-female transmission (Muzny et al., 2013; Sobel, 2012).

Finally, there is the hypothesis that exclusive male homosexuality has a microbial origin (Cochran et al., 2000). Its main shortcomings are that (a) there is no candidate pathogen and that (b) exclusive male homosexuality has been observed in social environments with limited opportunities for pathogen transmission, such as small bands of hunter-gatherers across pre-Columbian North America (Callender & Kochems, 1983). On the other hand, there seems to have been a relatively recent shift in European societies from facultative to exclusive male homosexuality, so something may have happened in the environment, perhaps the introduction of a new pathogen (Frost, 2009).

Both male and female homosexuality seem to have multiple causes, but it’s likely that various pathogens have exploited this means of spreading to other hosts.


This is a fun subject when it concerns silly mice or zombie ants. But now it concerns us. And that's not so funny. Can microbes really develop such demonic abilities to change our private thoughts and feelings?

It does seem hard to believe. Perhaps this is an argument for intelligent design. After all, only an all-knowing designer could have made creatures that are so small and yet capable of so much ... things like inducing abortion, breaking up marriages, and altering normal sexual desires. Yes, such an argument could be made.

But I don't think anyone will bother.


Apari, P., J. Dinis de Sousa, and V. Muller. (2014). Why Sexually Transmitted Infections Tend to Cause Infertility: An Evolutionary Hypothesis. PLoS Pathog 10(8): e1004111.

Caldwell, J.C., P. Caldwell, and P. Quiggin. (1989). The social context of AIDS in sub-Saharan Africa, Population and Development Review, 15, 185-234.

Callender, C. and L.M. Kochems. (1983). The North American Berdache, Current Anthropology, 24, 443-470. 

Cochran, G.M., P.W. Ewald, and K.D. Cochran. (2000). Infection causation of disease: an evolutionary perspective, Perspectives in Biology and Medicine, 43, 406-448.

Flegr, J. (2013). Influence of latent Toxoplasma infection on human personality, physiology and morphology: pros and cons of the Toxoplasma-human model in studying the manipulation hypothesis, The Journal of Experimental Biology, 216, 127-133. 

Frost, P. (2009). Has male homosexuality changed over time, Evo and Proud, March 5

Kuchar, G. (2001). Rhetoric, Anxiety, and the Pleasures of Cuckoldry in the Drama of Ben Jonson and Thomas Middleton, Journal of Narrative Theory, 31 (1), Winter, pp. 1-30. 

Mormann, K. (2010). Factors influencing parasite-related suppression of mating behavior in the isopod Caecidotea intermedius, Theses and Disserations, paper 48 

Muzny, C.A., I.R. Sunesara, R. Kumar, L.A. Mena, M.E. Griswold, et al. (2013). Correction: Characterization of the vaginal microbiota among sexual risk behavior groups of women with bacterial vaginosis. PLoS ONE 8(12): 

Reed, B.D., P. Zazove, C.L. Pierson, D.W. Gorenflo, and J. Horrocks. (2003). Candida transmission and sexual behaviors as risks for a repeat episode of Candida vulvovaginitis, Journal of Women's Health, 12, 979-989. 

Schmid, J., P.R. Hunter, G.C. White, A.K. Nand, and R.D. Cannon. (1995). Physiological traits associated with success of Candida albicans strains as commensal colonizers and pathogens, Journal of Clinical Microbiology, 33, 2920-2926. 

Sobel, J.D. (2012). Bacterial vaginosis, Wolters Kluwer, UpToDate 

Zhong, G., L. Lei, S. Gong, C. Lu, M. Qi, and D. Chen. (2011). Chlamydia-Secreted Proteins in Chlamydial Interactions with Host Cells, Current Chemical Biology, 5, 29-37


JayMan said...

Good post!

"(b) exclusive male homosexuality has been observed in social environments with limited opportunities for pathogen transmission, such as small bands of hunter-gatherers across pre-Columbian North America (Callender & Kochems, 1983)"

Satoshi Kanazawa did an extensive review of the ethnographic evidence, and finds no evidence of homosexuality in pre-agricultural groups.

Anonymous said...

So, just as advanced Western societies have decided that sexual freedom (especially of the LGBTQ type) trumps freedom of speech, association, religion, etc., it suddenly seems that the sexual revolution may express, not individual autonomy, but the Darwinian imperatives of microbic infections.

Dr Caveman said...

Great read. Toxoplasmosis also affects men and women - men become dumber, women more outgoing and promiscuous

Evopsy said...

Can’t we go further?

Sex is incredibly inefficient to transmet human genes: the ratio number of children / number of sex relations is near zero. But it is not at all inefficient to transmit bacterial genes, actually it is even one of the most efficient way to do it: it gives prolonged direct physical contacts. So, can’t we say that the main objective of sex is to transmit bacterial genes instead of our owns?

I had written on this hypothesis on Evopsy ("A quoi sert le sexe ? A transmettre les gènes du microbiome…”) and in the 3rd Ed. of “Pourquoi les femmes des riches sont belles”.

subpatre said...

"Can microbes really develop such demonic abilities to change our private thoughts and feelings?"

Take a look at rabies and the other lyssavirus'. They gather strength in the muscle tissues, then move up neural pathways into the spinal chord to the brain. Once in the brain, a large number migrate to the saliva glands. The virus then neurally inhibits saliva swallowing while simultaneously provoking the rage response. After a while in this phase, the virus then paralyzes its host and kills by paralysis.

100% fatal, it has survived since earliest recorded history. Very impressive, and scary, for a single RNA strand.

Santoculto said...

I really believed for a long time that such hbd movement was composed of very smart people, but I'm starting to seriously doubt it. Or I'm a super-crazy megalomaniac, or I'm right.

One of the many fools problems of observation, causality and correlation, intuitive logic of you in relation to this matter, this hypothesis is based on the idea that promiscuity is a socio-environmental vector for spreading pathogens but not monogamy. Why is it *

Simple, because it suits them. Why are conservative and will do exactly what the Liberals have done since the end of World War II, using highly sophisticated words and the device status and 'meritocracy' great civilizations to push their agendas group.

It makes no sense that only one group of humans is the vector of pathogens and the other does not, it has the same origin.

Another time I will comment on the pathogenic nature of sex, sexual reproduction and not just the obligatory male homosexuality, this is ridiculous.

Santoculto said...

And this stupid Jaymême and their absolute certainties. It's for laughter even the growing evidence of complete lack of parsimony, humility, and especially any holistic connection with morality or civil rights (the ridiculously stupid human idea of ​​imposing laws based on consensus where the shares personal nature of individuals are publicly discussed, that is, people decide on the lives of others, completely ridiculous but expected this nonsense called humanity).

We will decide if guy can have sex with another guy.

Of course, if there is no evidence that male homosexuality compulsory existed in primitive human societies, where the risk of infection by pathogens is substantially significant, after all, hunters collectors are all the time coming in direct contact with nature ... then we spread to every place that male homosexuality is an illness mandatory,

after all, she is only caused by pathogens (nope, all sexuality is itself the result of pathogens).

The most unbelievable or not so unbelievable is that guys like these will continue to be cheered because of his great intelligences that course, been proven in iq tests, as well as for his great skills to keep sick a long academic career, having ideas 5 in 5 years, if you are not lucky enough to have ideas that can be easily refuted.

Incredible, we will continue to push this objectively scientific idea, that very soon, we create ways to end the mandatory male homosexuality.

If we were to actually end up with problems of mankind, we should start with the men who are largely responsible for much of the stupid conflicts, penian conflicts.

People are so empathetic ... I am a very empathetic guy and I'm seething with anger at the world that these filthy minds of high iq and arrogance, try to sustain uselessly.

Anonymous said...

@ JayMan

Don't you generally dispute environmental explanations for behavior such as this?

Santoculto said...

The Hbd movement is also pushing that environmental factors do not exist, are just fairy tales. The problem is not that environmental factors do not exist, that in fact it is not actually. The problem is that the vast majority of people often confuse correlation with causality at all times. Therefore, the typical liberal thinking, summarily disregards any role of genetics. In turn, the Malthusian and Darwinian, conservative movement that preaches the exact opposite is true, ie, we are puppets influenced by our genes, which actually is not in us, we are just vectors.

Clearly both are wrong. The problem is precisely that, is widespread to genetic or environmental.

These people despise the natural variability, are denying the very theory of natural selection Darwin.

Anonymous said...

If the purpose of sexual reproduction is to win a never ending arms race with deleterious mutations and if that arms race was harder in the tropics then bugs that encourage promiscuity might make sense. They'd be net benign in that context.

Also the local population might have some resistance so a bug that made a local behave a little different might cause a more extreme change in someone from a more distant region.

If this idea is correct I think there ought to be a dramatic change in average behavior in China either already or in the near future as a result of so many working in West Africa as presumably they wouldn't have any resistance at all.

Peter Fros_ said...

Hi JayMan,

Thanks! Please see my reply on


"Freedom" is a social construct. We have social structures that create opportunities to do things that would be impossible if we were all acting alone and by ourselves. Liquidating these social structures, like the bonds of family and ethnicity, has the perverse effect of decreasing human freedom.


Philippe, je suis content de lire tes commentaires sur mon blogue!

A sexually transmitted pathogen has a higher chance of reproducing itself through each act of human sex, but the chances of its "offspring" surviving and reproducing are much lower. In contrast, a human couple has a lower chance of reproducing with each act of sex, but their offspring will have a much higher chance of surviving and reproducing.


I agree. People think that the human brain is somehow off-limits to microbes. They're wrong.


Wait a minute! Infection by a pathogen is an environmental factor and not a genetic one. If I was such an uncompromising genetic determinist, I would be arguing that homosexuality and other "alternate" forms of sexual behavior have a genetic cause. That's not my argument.


You raise a key point. If the hypothetical "cuckold envy" pathogen evolved in sub-Saharan Africa, the local population would have developed some resistance to it over time. It would be interesting to see whether resistance to Chlamydia is stronger there than elsewhere.

Santoculto said...

You did not understand my point. I'm not arguing that it is clear that pathogen infection is an environmental cause. But wait a minute, hmmmmm ...
You have 30 different people in the same room and only 3 'contracts the pathogen' that 'causes' homosexual behavior, say so. Does it have no genetic cause too ??

Are there more cases of gay blacks than whites,too much cases? Does promiscuity is a bad thing or you're taking this issue to a conservative perspective?

Will not you or Jaymême show me Galup data showing that only 4% of Americans declare themselves gay, when the percentage is likely to be much higher. And do not give me the argument

"See ... Whites are 3% gay, blacks are 4%, is statistically significant '

It is not.

It is extremely easy to deconstruct the attempt that you guys are doing to pathologize homosexuality.

Example, there are cases of homosexual behavior in nature, we are not just talking about minorities but of entire species of hermaphrodites. Just now, in the Hbd Chick blog, I learned that kangaroos have three vaginas, an anomaly ??

Get out your conservative, Malthusian and Darwinian perspective and look at entering other fields. More beneficial to their academic career and I am not speaking in a political sense, but for personal intelectual enrichment.

I can not understand why you guys always avoid comment on the pathological nature of sexuality per se. It is very strange that you guys avoid talking about this very important detail.

You guys need to abandon the traditional scientific method by multiple perspectives, objectifying abstractions so you can analyze every piece, every hand, every detail of it and realize that unilateral-deterministic theories and hypotheses cannot be temporally strong to resist because you not capture details and big picture.

Anonymous said...

Wait a minute! Infection by a pathogen is an environmental factor and not a genetic one. If I was such an uncompromising genetic determinist, I would be arguing that homosexuality and other "alternate" forms of sexual behavior have a genetic cause. That's not my argument.

What's the basis for considering environmental explanations for phenotypes of sexual behavior and libertinism? You usually eschew environmental explanations for behavioral phenotypes, including "liberal" behaviors. You also usually eschew claims of behavioral manipulation by complex organisms like humans and favor genetic explanations over such claims. What's the basis for considering manipulation by microorganisms while rejecting manipulation by more complex organisms?

Anonymous said...


Why are these liberal sexual attitudes and behaviors being explained as caused by microorganisms? Why not by "outbreeding" in Medieval Europe or by fishing and shellfish collection in Mesolithic Europe, which are usually used to explain liberal attitudes and behaviors? Seems rather inconsistent and arbitrary.

KD said...

Good article until the ridiculous shit at the end.

Unknown said...

what about associating syphilis and insanity? if sane, please comment.

Anonymous said...

I will leave this comment free to anyone who will take something from it.

Sistemic Candida Albicans actually make you crave for sugars, behave in irrational ways and a lot of mental and even hormonal symtomps.

I don't have here the exact information, but if you investigate or (worst) suffer it you may realize that those demons can make you violent or autistic.

I suspect that Candida Albicans, who thrives on sugar and flours, is a demon that controls and co-evolve with the people who have been living in cities and agricultural (non hunter-gatherer) since the dawn of Civilization, in the Fertile Crescent.

Some traits (I repeat again, I don't have here the exact information, I am a sufferer of it myself, now curing myself) can be pretty advantaging.

I am astonished that I haven't seen studies or corcern in Hbd circles. Because due to the high carb, high sugar unnatural diets in modern day a lot of people probably have more Candida Albicans in their body than centuries in the past.

Rambling this comment further, the origins of Civilization, a subversion of Nature...

The effect of pathogens, the subversion of Nature and the deliberate falsication of reality are key to understand what's going on in the World.

Maybe inside the vast masses of people, a group of them, with Candida Albicans and maybe some other patoghens, alongside with a extremely rational mind and an unshakeable will power to dominate others or seek revenge from the humiliations of the past, adoptep the strategy of the pathogens that were inside of them.

Think about the World, the Modern World, just a moment.

Maybe some underground force acted like a Systemic Candida Albicans.

It make the World turn to their way.

It release toxins and corruption through the body (the World).

It controlled the World, the same as Candida Albicans make an human being adicted to diets high in carbs, sugar and alcohol. (Food related to the feminization of Mankind, also).

Candida Albicans can spread through the whole body and you may never realize what is happening to you.

You could be labelled with some psychiatric illness, some sinusitis, some hurt toe-nails.

You even may start to rationalizate the way you are. "I am introverted", "I am weak", "I love that food".

But the main problem is inside of you, have been taken power over you since a lot of time and probably will kill you.

If the fungus will continue living when the corpse dissapeared...According to Wikipedia or some other source the Candida consume the body after death.

I agree with this. Demons exist. And we must think if some population have co-evolved with those demons, melting in one sole force.