The Second Brain describes the substantial amount of nervous system needed to run the digestive tract.

For example, stomach acid dissolves meat. How do you manage to avoid digesting yourself? Partly, there’s a chemical reaction which makes stomach acid outside of your cells, and there’s also base to neutralize the acid on the way out of your stomach– and it has to be made in the right amount at the right time.

As I recall, the book doesn’t include the effect of emotions on all this– explaining the system without including emotions is complicated enough. It does suggest that some ailments which are attributed to the organs might actually be problems with the neurological control system.

I haven’t seen anything recent about this because the attention has been going to the microbiome. Has anyone seen something more recent than 1999?

There's been recent news that a species of mustard can have paired mutant genes but still produce normal offspring. The current tentative explanation is that the plant (and perhaps many other species) maintains a copy of the good genes--perhaps its entire genome--which can sometimes override mutations.

While I generally prefer that the world be weirder than it looks, I'm betting that the particular mutation is unstable and has a small chance of reverting to the normal form on its own.

biology gets complicated

An unusual game is being played out in the Coast Range of California. Three alternative male strategies are locked in an ecological "perpetual motion machine" from which there appears little escape. As in the rock-paper-scissors game where rock beats scissors, paper beats rock, and scissors beats paper, three morphs of lizards cycle from the ultra-dominant polygynous orange-throated males, which best the more monogamous mate gaurding blues; the oranges are in turn bested by the sneaker strategy of yellow-throated males, and the sneaker strategy of yellows is in turn bested by the mate guarding strategy of blue-throated males. Each strategy in this game has a strength and a weakness, and there is the evolutionary rub that keeps the wheels spinning.

The description seems to view the cycle as a problem ("little escape"), but I can't see that it's inferior to species with a stable male strategy. The most obvious thing that could destabilize it would be oranges developing the ability to identify yellows as males.