In Scientific American, we learn “ThNeuroscience of the Gut: Strange but true: the brain is shaped by bacteria in the digestive tract” (Robert Martone, April 19, 2011):
We human beings may think of ourselves as a highly evolved species of conscious individuals, but we are all far less human than most of us appreciate. Scientists have long recognized that the bacterial cells inhabiting our skin and gut outnumber human cells by ten-to-one. Indeed, Princeton University scientist Bonnie Bassler compared the approximately 30,000 human genes found in the average human to the more than 3 million bacterial genes inhabiting us, concluding that we are at most one percent human. We are only beginning to understand the sort of impact our bacterial passengers have on our daily lives.
Then how come we don’t all dissolve in the chlorine in the swimming pool?