Humans need a lot of nutrients for brain operation, so it makes sense that we would have a sophisticated system for working with the gut flora and fauna to supp

Humans need a lot of nutrients for brain operation, so it makes sense that we would have a sophisticated system for working with the gut flora and fauna to support them so that they can help us digest food effectively. If this is the case, in a sense we then we invite the gut inhabitants, and ask them what they want so they can help us. I think it's reaching a bit to describe this as 'gut bacteria control the brain'.