http://www.newsweek.com/brain-cells-gut-evolution-brain-digestive-health-mice-957386

We have brain cells in a very unexpected place in our bodies, our digestive tract. Known as the enteric nervous system, these neurons are commonly referred to as our 'second brain', but a new study from Australia suggests these neurons may actually be the very ‘first brain’ that our mammalian ancestors evolved.

For the new study, published online in the Journal of Neuroscience in late May, the researchers detail their discovery of the millions of neurons in the gastrointestinal system of mice.