A surprising finding of the Human Genome Project was the small number of genes actually discovered (c. 24,000), compared to the genome of much simpler organisms.
Some researchers started to speculate that human physiology may depend to a significant extent on other genes we 'carry' - in fact, the genes of the large number of microbes residing in the human body!
In 2007, the NIH launched the Human Microbiome Project to catalog the microorganisms living in and on the human body. And another discovery - the 100 trillion bacteria in the adult human contain 4 million bacterial genes - sometimes referred to as the “other human genome.”
The new model of genetics has already taught us that the the human genome is more fluid, dynamic and responsive to all that we experience (including what we eat, how we think, feel, speak, and act) than previously thought. How this activity changes in response to our life experiences is referred to as “epigenetics.”
Regardless of the nature of the genes we inherit from our parents, dynamic change at this level allows us more influence on our fate than we ever realised.
And now we are discovering that it's not just human genes but microbial genes that play a role in our destiny. The microbiome is intimately linked to its human 'host' by synthesising molecules with direct effects on the human immune system, such as modifying the epigenome and regulating metabolism.
Another reason why it's all about the Gut....