Is There a Microbial Component to Religious Rituals?
Alexander Y. Panchin, Yuri V. Panchin, Alexander I. Tuzhikov
The human body contains a plethora of microorganisms, including bacteria that inhabit all of our surfaces: the skin, cornea, guts, mouth and sexual organs. Recent research suggests that gut microbes may not only affect certain metabolic processes, but also affect the human nervous system and certain behavioral phenotypes including cognition, mood, sleep, personality, eating behavior, and even a variety of neuropsychiatric diseases. The human gut microbiome might play an important role in the development of anxiety, depression and Alzheimer disease. This phenomenon was labeled “the microbiome-gut-brain axis”. Furthermore, it has been suggested that the modulation of gut microbiota may be a viable strategy for the treatment of certain mental disorders. Lab experiments on animal models show that treatment with specific strains of bacteria may affect the central nervous system by differentially altering GABA receptor expression in several regions of the brain. It was also shown that mice free of specific pathogens display different behavior patterns than germ free mice and that the transfer of intestinal microbiota may influence target host behavior. One suggested mechanism of interaction between microbes and the hosts nervous system is through the production and utilization of behavior-altering neurochemicals, some of which can be found simultaneously in different domains of life.
Many parasites are known to dramatically affect the behavior of their animal (metazoan) hosts. Ophiocordyceps unilateralis is a fungus that behaviorally manipulates Camponotus ants to remain in conditions that are optimal for the fungal development up to the moment when the host dies. The Wolbachia bacteria are widespread parasites of arthropods and nematodes and may influence their hosts mating behavior in a way that facilitates the reproduction of the parasite. Another fascinating example is the crustacean parasite of crustaceans Sacculina carcini that can make infected male crabs (Carcinus maenas) appear and behave as if they were female, taking care of Sacculina eggs as if they were their own.
The rabies virus is capable of moving along axons from the point of initial infection towards the central nervous system where it causes progressive encephalitis. The symptoms induced by the rabies virus in animal hosts include dramatically elevated levels of aggression which lead rabid animals to bite, spreading the infection.
Another example is the Dicrocoelium dendriticum Trematoda flat worm larvae that appears to modify the behavior of host ants by having them climb tall blades of grass at night and fixate themselves with their mandibles. This behavior makes ants (and the parasite inside) likely to be consumed by cattle, thus spreading the parasite to their definitive hosts. This host-controlling parasite is capable of infiltrating the ants nervous system, typically the subesophageal ganglion. The parasitic Nematomorph hairworm, Spinochordodes tellinii affects the behavior of its host Meconema thalassinum by making this grasshopper more likely to jump into water, where the adult parasite reproduces and the host usually perishes. This process was found to be associated with differential expression of proteins specifically linked to neurotransmitter activities in the host.
A remarkable example of host control is observed when the larvae of the parasitic wasp Glyptapanteles sp. induce their caterpillar hosts (Thyrinteina leucocerae) to behave as bodyguards of the parasitoid pupae after the larvae exits the host. It was also shown that this behavioral modification of the host leads to a two-fold reduction in mortality of the parasitoid pupae with no evident benefits for the caterpillar. The Barley yellow dwarf virus affects the feeding behavior of Rhopalosiphum padi aphids: infected aphids prefer to feed on uninfected plants, spreading the infection. Recently it was shown that the malaria parasite Plasmodium falciparum affects the attraction to nectar sources and sugar uptake of the mosquito Anopheles gambiae.
Around one third of the human population is estimated to be hosts of the parasitic protista Toxoplasma gondii, although infection rates vary by country. This parasite can be transmitted by cats, the definitive hosts of Toxoplasma gondii, and its cysts can be localized in the brain. Although toxoplasmosis is considered to usually have subclinical effects on humans, it was found to be associated with altered behavior in humans and rodents. In particular the presence of Toxoplasma gondii was linked to suicidal self-directed violence and increased suicide rates in women. Latent toxoplasmosis was found to be associated with increased risk of traffic accidents and with the perception of pleasantness of cat urine odor in a gender-dependent manner in humans. Some associations between personality traits and Toxoplasma gondii infection are also gender-specific. For example, infected men are less intelligent and infected women are more intelligent, although a casual relation is yet to be proven. Rodents infected by Toxoplasma gondii display more preference to feline odors and are more likely to expose themselves in the open and become prey for predators. Toxoplasma gondii infection has been proposed as a factor that influences human culture, as its latent prevalence explains a statistically significant portion of the variance in aggregate neuroticism among human populations.
We reviewed some of the most distinguished behavior-altering parasites from different domains of life. We believe that a few additional parasites should be mentioned exclusively due to their exotic nature despite the fact that they are not currently known to alter host behavior in ways that facilitate their transmission. Prions are agents composed of misfolded proteins that can cause degenerative neurological disorders such as Creutzfeldt-Jakob disease and kuru (also known as the “laughing sickness”). Kuru is an infectious disease that was transmitted in the course of ritualistic cannibalism in Papua New Guinea. Also a unique infectious cancer in Tasmanian devils (Sarcophilus harrisii) while not known to affect host behavior benefits from the preexisting aggressiveness of the host species that allows it to spread. Another notable example of transmissible cancer is the canine transmissible venereal tumor.
The variety of parasites that can affect host behavior suggests that the phenomena of parasitic host control might be more common in nature than currently established and could have been overlooked in humans. This warrants a detailed search for parasitic organisms that affect human behavior. One approach to search for “invisible” microbes that influence behavior is by comparing the microbiomes of control subjects and humans that consistently engage in irrational ritualistic behavioral activities, which contribute to the spreading of parasites and infections.
The modern anthropological view on religion is that it is a cultural meme that replicates through social communication. While the meme itself may influence behavior, religious icons are known to be vectors of infectious diseases. Most major religions have rituals that are likely to promote the transmission of infections. This includes circumcision, Christian common communion chalice, the Hindu ‘side-roll’ and Islamic ritual ablution as well as the Hajj congregation in Mecca. For example, the latter is specifically associated with outbreaks of meningococcal disease.
Consider the Hindu ‘side-roll’. It is a ritual that takes place during the 25 days of the Hindu festival period: devoted men lie on the ground and roll sideways around the Nallur temple in Jaffna for approximately 600 meters, usually with exposed torsos. The frequency of ritual performance is significantly associated with Cutaneous larva migrans, also known as creeping eruption of the skin, that is caused by parasitic worm larvae from domestic canine, bovine and feline hosts, although recent sanitary measures have reduced the incidence of this particular pathology.
Mortification of the flesh and different forms of self mutilation are present in a variety of religious cultures including many indigenous cultures. Some claim that extreme practices of mortification of the flesh may be used to achieve spiritual experiences. Self inflicted wounds as any wounds provide additional routes and possibilities for infections.
“Holy springs” and “holy water” have been found to contain numerous microorganisms, including strains that are pathogenic to humans. The Ganges River probably tops the list. This river is considered sacred in Hinduism, while its waters are considered both pure and purifying and are used for the preparation of traditional medicines. However an estimated 200 million liters or more of untreated human sewage is discharged each day into the Ganges River, its waters contain multiple pathogens and bathing in this water is associated with the development of multiple diseases, including cholera.
Also many religions are centered on sacred relics that are worshiped and frequently kissed by multiple people and thereby can act as vessels for microbial transmission. Crosses, icons, Bible covers are kissed in some denominations of the Christian tradition, the Black Stone (the eastern cornerstone of the Kaaba) is a relic that is kissed by millions of Muslims, kissing of the Wailing Wall is a religious tradition for the Jewish. It is unlikely, but possible that the rejection of condom use, vaccination and use of antibiotics present in some religious cultures, as well as the sacred status of specific domestic animals (possible definitive hosts to the parasites) may also be related to microbial host control. Finally, it has been noted that many parasites eliminate their hosts reproductive potential as they channel all available resources to maximize their own reproductive success. Coincidentally celibacy is commonplace for holy individuals that are most devoted to their faith such as monks or nuns.
Thus it is possible that various religious practices could represent biomemes: manifestations of a symbiosis between informational memes and biological organisms. This concept is somewhat similar to the fictional midichlorians of the Jedi Order from the popular series “Star Wars”.
Two particular parts of the human body seem to be most promising for the search of behavior-altering parasites. First of all, the human gut microbiome may be of interest in light of the microbiome-gut-brain axis concept. Another promising area to search for behavior-altering parasites is the human brain. Several organisms that can bypass the mammalian blood–brain barrier and produce a latent infection without obvious symptoms are currently known. In mice with latent toxoplasmosis, Toxoplasma gondii cysts can be found in various regions of the brain, especially in the olfactory bulb, the entorhinal, somatosensory, motor and orbital, frontal association and visual cortices, the hippocampus and the amygdala. In humans the brain also appears to be an important site for Toxoplasma gondii cyst formation and the parasite is capable of infecting a variety of brain cells, including astrocytes and neurons.
Taeniasis (infection by the larval stage of a pig tapeworm Taenia solium) is characterised by mild or no symptoms (most patients are clear of any symptoms), thus the infection can remain undetected. Taenia solium commonly infects the central nervous system, causing neurocysticercosis. Epileptic seizures are the most common presentation of neurocysticercosis (actually, a leading cause of seizures and epilepsy in some areas) and generally represent the primary or sole manifestation of the disease, however not all patients with diagnosed neurocysticercosis have seizures. Interestingly, clinical observations support an association between religious experiences during, after, and in between epileptic seizures. Most patients with cerebral schistosomiasis are asymptomatic or have mild and nonspecific symptoms. The cerebral infections by the flat worms Spirometra mansoni and Paragonimus westermani have nonspecific signs and symptoms such as headaches and seizures. Coincidentally, headache status at baseline was found to be positively associated with frequent religious attendance (but not attendance of other social events) in one study, consistent with previous findings.
Herpesviridae, Paramyxoviridae, Rhabdoviridae, Picornaviridae, Retroviridae viral families include strains of neurotropic viruses. Of these herpes simplex and varicella zoster virus are known to cause latent infections of nerve tissues. While no one seems to have published any metagenomic projects specifically devoted to the search of microorganisms in seemingly healthy human brains, a metagenomic analysis using cloning and sequencing of 16s rDNA of brain abscesses revealed a number of previously uncharacterized bacteria, however their presence is probably related to the observed clinical conditions. In any case it seems that a seemingly healthy brain or a brain of a human with only mild unspecific symptoms might not be as sterile as commonly assumed.
Presentation of the hypothesis
Some microorganisms would gain an evolutionary advantage by encouraging human hosts to perform certain rituals that facilitate microbial transmission. We hypothesize that certain aspects of religious behavior observed in human society could be influenced by microbial host control and that the transmission of some religious rituals could be regarded as a simultaneous transmission of both ideas (memes) and organisms. We call this a “biomeme” hypothesis.
Other types of behavior may also be influenced by microorganisms. We focus on the example of religious rituals because the facilitation of microbe spreading through some rituals seems evident, their adaptive role for humans is debatable and there seems to be a positive association between parasite-stress and religiosity.
Testing of the hypothesis
Our hypothesis makes several testable predictions.
1. We predict that next-generation microbiome sequencing of samples obtained from gut or brain tissues of control subjects and subjects with a history of voluntary active participation in certain religious rituals that promote microbial transmission will lead to the discovery of microbes, whose presence has a consistent and positive association with religious behavior. We believe that this is the most important prediction and it should be tested in a framework similar to other comparative microbiome studies that have become quite common. This association should be casual, thus complying with the reassessed modern version of Kochs postulates.
2. Religious behavior could be positively associated with immune system deficiency. For example, while Toxoplasma gondii infections are usually latent, cerebral toxoplasmosis becomes one of the most prevailing opportunistic infections in HIV-infected patients. Immune system deficiency makes humans more susceptible to all kinds of parasites most certainly including those hypothetical ones that could affect human behavior. However, it would probably be difficult to find appropriate control subjects to test this prediction. Participation in religious rituals might be more appealing to those lacking good health or could be influenced by various unaccountable social factors. Not to mention the fact that this is a rare case when control subjects may constitute a minority of the world population. However, differences might also be observed between currently healthy individuals with different susceptibility to infection due to inherited factors. For instance, certain SNP variants in human MHC proteins, cytokines and cytokine receptors, as well as the diversity of T-cell receptors and antibodies might be associated with active and voluntary participation in religious rituals.
3. We expect religious behavior to be negatively associated with certain medical treatments against infections (such as antibiotics). We cannot make definite predictions about which treatments might influence the inclination to perform specific religious rituals as we do not know the precise nature of the hypothetical behavior-altering organisms. However, it might be helpful to follow-up the future religious practices of children that have been subjected to different treatments on similar occasions at baseline. Interestingly, our hypothesis also predicts a decline of religious activity in human societies with improved sanitation.
4. There might be changes in religious activity following dietary changes that are known to affect the human gut microbiome composition. Interestingly, fasting is a widespread religious ritual. Fasting is known to reduce total gut bacteria and affect the gut microbiome composition as shown for hamsters, Burmese pythons, mice and ground squirrels.
5. Candidate microorganisms predicted to influence an individual’s participation in religious rituals should also be found on the surfaces of important religious relics or other items involved in these rituals.
It seems that something like Toxoplasma gondii would be a good preliminary candidate for the role of our hypothetical microbe that promotes religious behavior as it is prevalent and widespread (as religious practices are) and its infection is associated with some behavioral traits and it is capable of latently residing in the human brain. Coincidentally, the sacred status of cats, definitive hosts of Toxoplasma gondii was part of the ancient Egyptian religious tradition for centuries. To our knowledge, no research on the association between toxoplasmosis or similar infections and religiosity has been performed, thus such an association could have been overlooked.
Interestingly, a number of studies have suggested that Toxoplasma gondii infection is an important risk factor for the development of schizophrenia and depression in humans and in mice models. Toxoplasma gondii infected mice display impaired learning, memory capability as well as more severe depression and stereotypy compared to controls. Meanwhile, religious delusions are commonly found in patients with schizophrenia and by comparison with other patients who have schizophrenia, those patients with religious delusions appear to be more severely ill. Some studies report that religion is important for outpatients with schizophrenia and that their religious involvement is higher than in the general population, although unaccounted factors for this association may exist.
Implications of the hypothesis
We acknowledge the speculative nature of our hypothesis that the participation is some religious rituals may be influenced by microorganisms. It is quite possible that our hypothesis will not withstand rigorous testing. However, if proven true, it offers dramatic consequences for society, science, healthcare and religion. The history of science provides a number of examples when conditions that were not expected to have microbial origin turned out to be exactly of that origin. For example, Helicobacter pylori infection and not stress or spicy food (as it was commonly assumed) turned out to be the most common cause of peptic ulcer following the findings of Marshall and Warren.
Our hypothesis may provide insights into the origin and pervasiveness of certain religious practices. The discovery of novel microorganisms that affect host behavior may improve our understanding of neurobiology and neurochemistry, while the diversity of such organisms may be of interest to evolutionary biologists, psychologists and religious scholars. From the viewpoint of molecular geneticists it would be interesting to study the evolution of these hypothetical organisms and how their genetic variation relates to the variation of religious rituals.
Ethical questions may arise on whether it is appropriate to expose children to microorganisms that influence religious behavior if such exposure can be avoided. Studies will emerge on whether it is possible to modify ones religious behavior by using specifically designed medical interventions (such as antibiotics) or probiotics.
The possible hazards and epidemiological consequences of microorganisms that alter human behavior may need to be modeled. It may be of importance to understand what happens in microbial communities on the surfaces of important religious relics and casings that travel around the world, such as The Gifts of the Magi (relics associated with the life of the saint prophet of the Christian religion Jesus Christ) and popular sacred sites. Such relics and sites interact with hundreds of thousands of individuals from different geographical backgrounds providing a platform for microbial interchange and microbial sex (conjugation). These factors may play an important role in commensal and pathogenic microbial evolution. For example it was recently shown that the spread of certain antibiotic resistance genes in waterborne bacteria is associated with seasonal pilgrimages to sacred sites at the Upper Ganges River.
It can be argued that some religious rituals involve washing and bathing, avoidance of potentially contaminated food sources, restrictions on sexual partners and other practices that may actually reduce the parasitic burden of diseases. These forms of behavior might be entirely cultural or even inherent to humans who apparently have a hardwired and adaptive notion of “contagion”, or, in some cases, could be a result of competition between different parasites. In the case of washing it should be noted that the use of chlorinated or otherwise disinfected water for bathing is a relevantly modern trend, not all natural water sources are pathogen free (consider the Ganges River as an example) and in some cases washing may be associated with parasitic diseases such as schistosomiasis. Ritual washing might be both a way of sanitation and a way for parasite transmission, depending on the environmental context.
We would like to clarify that our hypothesis does not explicitly suggest the existence of specific microorganisms for each type of religious ritual (although this is possible), but rather the existence of microorganisms that make humans susceptible to acquiring a wide array of somewhat similar irrational ritualistic behavioral traits that facilitate microbial transmission. These behaviors may be shaped and diversified by culture.
It should be mentioned that there is ongoing debate on whether adherence to a certain religion provides a fitness advantage to humans or human societies. In this context we would like to clarify that our hypothesis is not about religion in general, but mostly about specific religious rituals that do not provide apparent benefits to those who perform them, but facilitate microbial transmission. Some examples of such rituals are mentioned in the introduction.
In agreement with our hypothesis, that certain forms of religious behavior may be influenced by microorganisms, a recent finding suggests that “religiosity, as measured by religious affiliation and religious participation and value, was positively correlated with all measures of parasite-stress, and religiosity was correlated more strongly with the prevalence of nonzoonotic infectious diseases than with zoonotic infectious diseases”. Nonzoonotic infections are those that can transfer from humans to humans. Parasite stress is also associated with homicide rates and child maltreatment and predicts authoritarianism in cross-national and cross-cultural samples. Our hypothesis provides an alternative framework and explanation for these findings.
We believe that next-generation sequencing approaches might help narrow down the search for microbes involved in host control especially with the help of automated taxonomic identification tools and that the brain and gut microbiomes are of particular interest in the context of our hypothesis.
From https://biologydirect.biomedcentral.com/articles/10.1186/1745-6150-9-14