words kurt hollander | images judith kim
I am not Mexican. I wasn’t born in Mexico, nor were any of my ancestors. I have, however, lived in Mexico City for twenty-three years and thus I consider myself a defeño (a resident of Mexico City), not because I talk like one or think like one, but because after having lived here for so many years and having eaten the food every day, I have incorporated a microscopic Mexico City within my body. Several of my inner organs, especially my large intestine, provide shelter to huge communities of local bacteria (as well as a mix of viruses, parasites, and amoebas), originally invaders or immigrants but now an integral part of my biological system, and with me until the day I die.
Just as major cities tend to be more cosmopolitan and richer in immigrant culture, so too do those of us who live in mega-cities host truly multicultural flora and fauna within our bodies. Only recently have scientists started identifying the microscopic civilizations residing inside the human body, and they have found distinct communities of local bacteria in our mouths, within our noses and lungs, on our skin, inside our vaginas or around our testicles, and deep inside our gut. Although some of these communities share certain species, each represents a different cultural mix, much like separate cities within a single nation.
Of all the colonies my body hosts, the greatest concentration of microorganisms exists inside my large intestine. Just as humans are divided into blood types, so too can they be classified by the different strains of bacterial colonies within their large intestines. No two human beings have the same mix of microorganisms inside them, and inhabitants of different cities are characterized by different micro-cities of microorganisms within them. Three distinct bacteria colonies have been identified so far (since only European intestines were examined so far a much greater variety within the inhabitants of more biologically diverse regions of the world, such as Mexico, must exist).
When geneticists recently began to map the human genome, they were shocked to find that the greatest amount of genetic material within the human body is not in fact human. A human body is comprised of approximately ten trillion cells, but within our large intestine alone there are ten times that many microorganisms. Most of these microorganisms are bacteria (as many as 1,000 different species), although viruses, amoebas, fungi, and protozoa are lodged in there as well. After having co-existed and co-evolved with humans for so many hundreds of thousands of years, and after having adapted their functions to our biological system, this vast, highly complex, and socially interactive micro–mega-city now acts as a virtual organ within our large intestine. We depend upon these billions of bacteria to help us assimilate vitamins, encode enzymes, regulate the immune system, and aid in the digestive process.
Scientists are only beginning to get a glimpse of how the micro–mega-city inside our gut interacts with our body. Our digestive tract has its own nervous system, a network of neurons so extensive and complex that some call it our second brain. Known as the enteric nervous system, this complex system of nerves embedded in the walls of our gut contains some 100 million neurons (more than the spinal cord or the peripheral nervous system) and is equipped with its own reflexes and senses. Contrary to what most scientists believed for so long, this second brain does not exist merely to control peristalsis and other mechanical processes. In fact, about 90 percent of the fibers in the vagus nerve, the largest direct connection between our gut and our head, carry information and instructions from our large intestine to our central nervous system, not the other way around.
The question that is currently being debated in the scientific community is what information and instructions does this second brain transmit to our central nervous system and, even more importantly, who is sending these signals? It turns out that the microorganisms that have colonized our colon use this neural connection as their own private hotline, calling in orders as well as taking calls from the upper brain. Our brain communicates with the microorganisms in our gut directly (by molecules released into the gut from neurons or immune cells) and indirectly (via changes in gastrointestinal movement and secretion, and intestinal permeability), while our gut microorganisms communicate with the human brain by means of receptor signaling, manipulating glandular activity or through direct stimulation of host cells in the gut lining.
This intimate interaction between humans and microorganisms is known as inter-kingdom communication and is much more frequent and important than previously suspected. The exchange of information and orders between the microorganisms in our gastrointestinal tract and the nerves in our brain is vital for maintaining homeostasis, while communication breakdowns are responsible for many illnesses. One of the most common inter-kingdom miscommunication turns out to be chronic ulcerative colitis (an illness I have long suffered from), in which, due to the misguided distress signals it receives from the bowels, the body overreacts to the presence of non-aggressive microorganisms by attacking its own large intestine.
Homeostasis depends upon the constant regulation of chemicals circulating between our gut and head. More than thirty neurotransmitters, including 95 percent of the body’s serotonin (a chemical directly linked to depression and mood shifts), flow through our large intestine, influencing our emotional state and our mental health. The extent to which microorganisms control our behavior, feelings, and thoughts, is still mostly unknown (they move in mysterious ways), but the fact that microorganisms, especially aggressive parasites, can manipulate us to serve their needs is widely accepted. Parasites can gain control over us by depleting our system of needed vitamins and minerals; by excreting toxins that weaken us; and by deactivating our immune system (making us even more susceptible to control by incoming parasitic viruses, bacteria, and other microorganisms); and are therefore able to modify human behavior in specific ways and for specific purposes. In addition, parasite infection in male human beings has been correlated to memory loss, shorter attention spans, greater risk-taking, lower rule-consciousness, increased violence, irritability and jealousy. Certain other parasites have been shown to make women more intelligent, generous, outgoing, friendly, and/or promiscuous. Many of these behaviors serve to make both men and women, each in their own way, ideal vehicles for the spread and survival of these parasitic species, through their spread to human and non-human hosts.
Acting in a direct way, certain common parasites such as Toxoplasma gondii (present in the majority of inhabitants of mega-cities) can cross the blood-brain barrier and directly provoke physiological changes involved in the development of schizophrenia, bipolar disorders, Parkinson’s disease, Tourette’s syndrome, and attention deficit disorders. Psychiatric illness (especially depression and mood swings) are much more co-dependent on gastrointestinal disorders than previously thought. Because of their invisible influence, parasites could be considered our biological unconscious, responsible in large part for our behaviors and for our personality flaws, as well.
Microorgansims are responsible not only for certain individual behaviors and mental disorders; they might also differentiate human behavior as a correlate of social class (people in the lower classes, especially in the developing world, are more likely to have parasite infestation due to poorer health care, differences in water quality, contamination by sewage, and low sanitation); and gender differences (men are twice as prone to parasite infections due to sex-specific behavior, morphology, and the fact that testosterone weakens the immune system). Even stereotypes can be blamed on parasites (for instance, certain parasite infestations most commonly found in large cities have been associated with a high level of neurotic behavior). One out of every four people (and one out of every three tourists) in Mexico City suffer from parasites, most without even realizing what they carry within their bodies (often parasites are only discovered during autopsies), and locals can play host within their bodies to hundreds of different kinds of worm parasites and over 70 kinds of protozoa.
Mexico City’s greatest cultural wealth is its biodiversity, especially the thousands of species of microorganisms that represent the city’s true indigenous inhabitants. Although microorganisms exist in all parts of the city, the working and lower class barrios in Mexico City (like the ghettos and slums throughout New York City’s history) concentrate within them the greatest diversity of microorganisms, and this is precisely where the greatest inter-species communication occurs.
Because their gut flora—decimated by poor diet, poverty, and stress—lacks the proper defenses, slum dwellers tend to suffer more from the diseases associated with parasites and thus live shorter lives. Excluded from the formal economy and vulnerable to dangerous governments and businesses, and open game for all types of aggressive parasites, the city’s poor must constantly create new strategies to survive, and thus slums have always been fertile ground for cultural creation. (To give just one example, the South Bronx of the 1970s and 80s, one of the most impoverished, unhealthy and “dangerous” neighborhoods in the world, gave rise to Salsa, rap, break dance and graffiti).
Although slum dwellers have the closest contact to parasites, it is in fact the upper classes that are so often portrayed as parasites. Capitalists, like parasites, exploit the weakness of other organisms and communities and suck other people’s life energy for personal profit. Just as antibiotics weaken gut flora and thus allow for more foreign penetrations, so too free-trade agreements weaken local industry and unions and pave the way for market exploitation and neo-colonialism, forms of economic parasitism. The drive to colonize new worlds and the willingness to slaughter millions of human beings for personal profit could very well have come from the widespread presence of parasites in humans after the plagues that ravaged much of Europe. Today, corporate global expansion continues to mimic parasitic activity, invading civilizations, transforming existing structures, extracting energy and ultimately depleting health and leading to the death of those same cultures. Lower classes barrios or slums, on the other hand, tend to resemble bacterial colonies, forging communities to pool resources and to defend their territory against invasion, and within these communities there exist greater cultural changes and innovation, as can be seen in local language, fashion, dance, and music.
Since human beings first emerged on the planet, microorganisms have used us as vehicles to perpetuate their own species, and they have always been one of the driving forces of our species’ development. Much of our civilization can be viewed as the result of our intimate relationship with creatures we can’t even see.
More than anything else, death brings humans to religion and god. The fear of death, the grief associated with the death of loved ones, or the realization of the inevitability of one’s own future death, has long inspired human beings to believe in forces beyond their control. Throughout the majority of our history as a race, death came mostly from the handiwork of invisible parasites, their existence unknown up until just a few decades ago. Thus, most human beings had no clue as to why their loved ones got sick and passed away, and this lack of knowledge inspired all kinds of flights of the imagination. Elaborate beliefs that attempted to make sense of senseless death emerged, as did superstitious behaviors, and over time some of these evolved into complex religions. Until microscopes were invented, humans searched for the meaning of life and death in non-natural realms, eventually giving rise to the discovery and belief in gods.
Bacteria are the great architects of life, for not only were they the very first life form on earth, but they have been intimately involved in the creation and evolution of all species. Like an “invisible hand”, bacteria are unseen and omnipresent, and being that they can replicate asexually ad infinitum, they are eternal and indestructible. Due to their prominent role in human death (being that, up until recently, infections and diarrhea were the number one cause of death among humans), bacteria can also be seen as the Holy Ghost or the Grim Reaper. Although I can’t actually see them, I believe in bacteria as others believe in their one, true God, and pray that they aid my body while I am still alive. In return I’m perfectly content with the idea that they will clean it to the bone once I’m dead and buried.