Parasites and us….
What if I told you that free will was a flawed concept? Ahh you say — of course, we are constantly being manipulated by advertising, fake news, politicians…and parasites?
In the Alien movies humans are carriers for an alien being that bursts from our stomach when usefulness as a host is done. But it’s a little disturbing realising that it isn’t as far fetched a concept. Well, hopefully not the grisly method of dying, but being a carrier of alien bodies. To put it bluntly, we are a menagerie of living entities or more scientifically — a holobiont. A host amalgamating other species or species that have integrated us….
Let me calm you down via an explanation from Nature magazine. ‘Living inside every person are trillions of micro-organisms — bacteria, viruses, fungi and other life forms that are collectively known as the microbiome’.
Admittedly ‘and other life forms’ is a touch worrying. However the point is that micro-organisms or microbes have been in existence for billions of years, nonchalantly carrying about their business. For the first time in c1665 microscopes advanced to magnify the real world approximately 250x. Microbes became visible to us. A decade ago, significant progress in sequencing technology in conjunction with the falling cost of scanning sizeable amounts of DNA data boosted our understanding of our composition. Ever since we have come to realise that these hanger ons are fundamental for the recycling of life, to the biosphere around us as well as our own good selves through our microbiome.
A National Geographic article estimates that there are 38 trillion microbes in a young adult male — slightly more than the number of cells in a body. Although microbes live in many organs in our body, the greatest area of concentration is in the intestine where 90% of them reside. But picture this. Within each of our cells we have between 20–25,000 genes. But it is estimated that the microbes we host are by a multiple in the hundreds of our cell offerings, a much more extravagant feast of genetic material able to wield and manipulate to thrive symbiotically within us.
Ed Yong, a talented science writer explains in a talk on his book:
‘I contain multitudes’ what exactly these busy bodies do within our gut. ‘They help to digest our food, releasing otherwise inaccessible nutrients. They produce vitamins and minerals that are missing from our diet. They break down toxins and hazardous chemicals. They protect us from disease by crowding out more dangerous microbes or killing them directly with antimicrobial chemicals. They produce substances that affect the way we smell. They are such an inevitable presence that we have outsourced surprising aspects of our lives to them. They guide the construction of our bodies, releasing molecules and signals that steer the growth of our organs. They educate our immune system, teaching it to tell friend from foe. They affect the development of the nervous system, and perhaps even influence our behaviour. They contribute to our lives in profound and wide-ranging ways; no corner of our biology is untouched. If we ignore them, we are looking at our lives through a keyhole’.
Advances abound in our knowledge of the gut microbiome. We now believe that several diseases are influenced by the health of these micro-organisms, from Parkinsons, multiple sclerosis, types of autism and certain cancers. Millions are being invested investigating the link between brain disorders and the intestine because being able to influence the gut is easier than manipulating the brain. Some say elements of our make-up affects out sleep, weight and moods through micro-organism communication with our brains and so there is a debate considering if we might be able to develop mental health therapies by influencing our intestine health. We have carried out successful transfers of the gut microbiome (faecal transplants) from a healthy donor to another to help to treat C difficile, an infection that causes serious diarrhoea and there has been some success in tempering autism. Eventually we may take back control by being able to deliver direct to the body healthy microbes either as prebiotics (compounds that healthy microbes can grow on) or probiotics (the microbes themselves) or even personalised medicine targeted at improving our microbiome.
Our skin microbiome is also fascinating. Did you know our skin covers roughly 2 square metres for an adult. Much of it dry and nutrient poor except around the hair follicles. Yet on the skin there are many organisms alive and flourishing. Nature suggests more than 1000 types of bacteria. Some researchers believe that there is strong communication between the bacteria, skin cells and the immune system which is how skin is repaired and bolstered against infection including some skin cancers. An imbalance in this relationship can cause eczema, skin ulcers and difficulty in healing from a wound.
But surprisingly there is some evidence to suggest that we are not borne with a microbiome; in the womb a foetus is unencumbered. It is only when the baby passes through the uterus that the micro-organisms present in the mother are ‘handed over’. It is proposed that the first sugars produced in breast milk nourish these microbes within the baby, building the ecosystem in the child so that they can have a healthy start to life. A controversy suggests that via a C-section an infant does not build up their microbiome effectively and could be why these babies are more at risk of disease in the first few years of their lives.
So is it so surprising that our personality and the core of our essence is influenced by our microbiome? Analysis of the gut microbiome reveals that people with extensive social networks tend to have a more diverse microbiome though I am unclear which way is the causality? Lower diversity has revealed higher levels of stress and worry. Considering the human microbiome has narrowed in variety over the last 50 years as many more of us live in an overly sanitised world; the human race has moved from the country to concrete and due to the progress of antibiotics that kill microbes — perhaps that is why chronic disease and mental health problems are on the rise? And then our microbiome changes as we age, under the influence of diet, stress, the environment and so astoundingly no two people have an identical microbiome. Some say that this uniqueness could be employed in forensic analysis — differentiating between people based on their skin microbiome much as we do with fingerprints.
Although we feel our microbes exist purely for our good — we shouldn’t forget that they are parasites, not active directly for our benefit but for theirs. We can’t call them allies as such but whilst our interests of survival are aligned it does not appear that they act against us (unless they end up in the wrong place). However that still leaves the philosophical question of are we a multi species entity or are we a human carrying some companions? And what does that mean for free will and who we are? Answers on a postcard please.