HOW human do you think you are?
Well, let’s play a numbers game: in terms of cell numbers, you have in the order of a trillion cells in your body, though this value varies greatly between people and is constantly changing within each of us. However, you have some ten times this number of bacterial cells within (and on) your body 1. So at one level at least, you are only 10% human.
Of course, bacterial cells are quite a bit smaller than your cells, so there’s room for the both of you, in you.
In terms of genes, the instructions that make you you, humans have about 30,000. Again, there are in the order of a hundred times this number of bacterial genes operating within and on your body 2. So at another level you are only 1% human.
Don’t worry though, of course you’re 100% human. Instead, we need to consider the extent of what being human actually is. Being human comes part and parcel with being a super-organism. We live in a symbiotic relationship with hundreds of different species of bacteria, without which we could not survive. Think of them as an invisible extension of your body’s innate defences, occupying every external surface, your skin, your gut, your eyes, ear, nose, and various other orifices.
There is mounting evidence to suggest that they influence our development; our physiology; our nutrition and metabolism; and immunity, where they play an important role from birth in educating our immune systems. They are your interactive suit of armour, both part of the environment and part of you. These communities of bacteria are referred to as the microbiome, and they are being investigated as part of the Human Microbiome Project, an effort by many research labs coordinated by the National Institute of Health.