What does this mean? Take bacteria for instance. They “work” in a symbiotic relationship with all life forms. To understand the significance of this we’ll need to go back in time – just a tad. Like three billion years (3 billion years) to when there were no recognizable life forms on earth, only a primordial ocean “soup”. Simply put, this soup contained a huge variety of bacteria (never mind where they came from – no one really knows).
Now, return to present times and follow me – it was from out of that primordial “soup” that life (as we understand it) developed. Furthermore – just to put things in perspective – the human body consists of somewhere between 30 and 80 trillion cells (no one is quite sure – it depends on the method of measurement used – volume or weight). But the number of bacteria in the human gut exceeds this by a ratio variously estimated at about 3:1. That’s right, there are estimated to be about 3 times more gut bacteria than cells in our body. Similarly, while the human genome has about 20 000 genes the gut biome has many, many times this – variously estimated at about 150 times this number.
Never forget, too, that we rely on out gut bacteria for our nutrition. Furthermore many different chemicals such as the brain chemical serotonin and many enzymes are produced in our gut. In fact without our gut bacteria we wouldn’t survive. They help digest everything we eat by reducing it to an easily absorbed form, which is then transferred to our blood affecting not only our metabolism but also our moods.
But the bacteria need us too – to feed them!
So now, because of the symbiotic relationship between us and them (and don't forget we are inextricably linked to all the Earth’s life forms through our bacterial ancestry) consider this scenario:-
Bacteria were here first – we (and all life forms) developed from the original primordial bacterial soup. Therefore, are we just a useful host for bacteria to live in – in our case, our gut biome (recall, there are more of them than cells in our body)? Remember also they get fed at regular intervals, interact with us via the vagus nerve – which connects the gut with the brain (in fact our gut may be considered our “second” brain as there are about 150 million neurons lining the intestines). This “communication”, travelling both ways along the vagus nerve, tells the brain “I’m hungry” or “I’m full” or “I don’t feel well” and then there is that mysterious “gut feeling” that “tells” us to do or not do something. Increasingly researchers are discovering links between our gut bacteria and our general health - physical, emotional and mental.
The food we eat affects our gut bacteria (negatively or positively) and in doing so, they affect our health and our moods (also negatively or positively).
So, how human are we - actually?
