How gut flora came to be?

[tiny101]

Hi there,

I am wondering how intestinal bacteria came to exist (in humans, or any species for that matter). Many articles discuss the evolutionary pressures that play a part in the development of gut flora, but never suggest any theories as to how they first came to be.

Any help would be much appreciated. Thanks in advance!

[canalon]

From a newborn, they start from their mom: The birth canal is not sterile. Then, as neither is their food, it keeps being enriched that way.

[mith]

probably has to do with their playing nice with the immune system.

[Darby]

Symbionts are common in many, many animals, so the basic relationship is ancient.