Who are we really?

At the beginning of this year I alluded to a piece I had written for the South African Agency for Science and Technology Advancement Young Science Communicator’s Competition. The competition results are now available and, unfortunately, I did not win anything. I’m not aware of anything preventing me from sharing my entry with you though so here it is.


If someone were to ask you who, or what, you are, how would you respond? Many people would say that they are themselves. That they are an individual human being. Many will take great pride in that statement and in how they are special and separate from the rest of the living world. While it is certainly true in one sense that we are individual human beings, the full truth is far more fascinating and wonderful. This because our bodies are not merely human but a mishmash of many species working together.

You may not realise it but you can’t truly say who you are without mentioning the countless bacteria that go into making you. And, trust me, no matter how often you wash, bacteria are an undeniable part of who you are. Inside your cells are small structures called mitochondria. They are the part of your cell that produces energy and without them you will die. Mitochondria are the remnants of ancient bacteria we engulfed long ago in our evolutionary history, even before plants and animals split.

Bacteria are all around us, all the time. There are between 860 000 and 11 million bacteria per cubic metre of air! They are tiny though, much smaller than a human cell, which is important when you need to understand how your body actually consists of ten times more bacterial than human cells! It’s not something to worry about, though, as those bacteria are not the harmful kind. In fact we depend on the bacteria living on and in us as much as they depend on us.

Interestingly, the bacteria with which we share our bodies are different for each person and are affected by age, lifestyle, the type of food we eat and chance. Scientists who looked at the bacteria in people’s belly buttons found that most had about 67 types living there but some had as few as 29 and others as many as 107. There are, of course, some which are common, although there were no bacteria that lived in everyone’s belly button. You probably also have a few species of bacteria which none of your friends or family have. Isn’t that exciting?

I’m sure you’re wondering what all those bacteria do, after all you probably only hear about them in a bad way for causing diseases like TB. Some are bad, but having the right bacteria living in you can actually make you a healthier person. Bacteria help us digest certain foods, absorb things we otherwise couldn’t and even make vitamins for us. Now just think of those thousands of bacteria in the air. Not all of them are harmless but if they try to live in us then our friendly bacteria will get rid of them. Since we are their home, and they don’t want strange bacteria trying to move in, they will protect us. If they aren’t there then the bad bacteria have a direct shot at us. This is a risk after a doctor gives you antibiotics, which kill both good and bad bacteria, and why you will then want to eat probiotics.

Probiotics are live bacteria which we eat because they are good for us. If you have taken antibiotics you will want to have probiotics to make sure the good bacteria start growing in you again to keep you healthy. Doctors are even starting to treat diseases purely with bacteria. It doesn’t sound very nice but they have started performing faecal transplants for some conditions. This essentially means that they take one person’s poo and put it inside a sick person. Gross, yes. But it does work and, once those bacteria from a healthy person take over, the patient is cured.

It’s not just bacteria that make us who we are, viruses are also a very real part of our identity, though in a rather different way. That’s a story for another time though. Now when someone asks who you are you are better prepared to answer. You are an individual human but you are also so much more. Your life is intimately entwined with, and dependent on, so many other species. Your own cells hold ancient bacteria and their modern cousins live inside you, outnumber your own cells and keep you healthy. Rather than being afraid of that we should be happy that we are so amazing and, even by ourselves, we are never alone.

Guarner, F., & Malagelada, J. (2003). Gut flora in health and disease. The Lancet, 360, 512-519.
Hulcr, J., Latimer, A. M., Henley, J. B., Rountree, N. R., Fierer, N., Lucky, A., et al. (2012). A Jungle in There: Bacteria in Belly Buttons are Highly Diverse, but Predictable. PLoS One, 7(11).
Landy, J., Al-Hassi, H. I., McLaughlin, S. D., Walker, A. W., Ciclitira, P. J., Nicholls, R. J., et al. (2011). Review article: faecal transplantation therapy for gastrointestinal disease. Alimentary Pharmacology and Therapeutics, 34, 409-415.
Whon, T. W., Kim, M., Roh, S. W., Lee, H., & Bae, J. (2012). Metagenomic Characterization of Airborne Viral DNA Diversity in the Near-Surface Atmosphere. Journal of Virology, 86(15), 8221-8231.


If you’re still interested in hearing more about how bacteria influence who we are and how we live I would suggest two summaries, one in Science and one in Nature, about a recent piece of work on the topic. New research is indicating the increased risk of heart disease from eating red meat could be due to bacteria in our gut digesting a chemical in the meat into a harmful by-product. What you eat is important but so is what lives inside you and eats what you eat.


1 thought on “Who are we really?

  1. Pingback: Two years, still going strong | Evidence & Reason

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s