Where does the intestinal flora originate?

Chris - The answer is that they come during your first moments of life. Unpleasant as it sounds, if you're a baby born the normal way, your first taste of life is a mouthful of muck, and it's your mum's muck, and it comes from the vagina, the perineum, and even from your mum's bum because there are bacteria that live in that area, all over that area, and as the baby comes out, they go all over the baby's face and mouth. They go then into the baby's intestines and they take up residence in the baby's gut. If you look upon it in one way, this is the perfect way to make sure that the bugs that the baby gets inside it are ideal for the kind of food it's going to be eating later, because the bugs mum has got are genetically right for her. They're also ideal for the kind of food she eats and subsequently, that's probably going to be the same food that the baby is going to eat when it's weaned. So, it make sense to get those bugs and get them inside the baby, and they then take up the right sorts of numbers and densities over time.

By the time you're about early teenage, the spectrum of bugs that you've got living in you and on you are more unique to you than your own fingerprints. And they stay with you for life until you're about age 60 and then they begin to change a little bit as the immune system begins to weaken slightly and the spectrum of those bugs can alter. But yes, the spectrum of bugs that you carry is unique to you and no one else has quite that same spectrum. Even your identical twin, if they have a slightly different diet or environment, can have a slightly different spectrum of bugs.