Weird, I kind of already considered them separate organs...

One brain gnawing on a bone and jerking off, the other reciting poetry and wondering if the stocks laid in for winter are sufficient

Maybe that's why reading someone's face is such a good method for determining another's mental state. Even when we try to control it there is something that gives us away.

So is emotion. That’s why marketing and propaganda targets it.

Freud is funny because there is usually a nugget of truth buried under all his bullshit. Like, not everybody wants to fuck their mom like he did but the way your parents raise you will determine how you attach to others.

And it might even be that these different personality pieces (Id, Ego, Superego) actually have different locations in the (different) brain(s), (which would be pretty awesome - Freud with his limited information actually having glimpsed structural information about our nervous system would be insane), distributed in the way you just mentioned. Many subconscious decisions depend on very basic impulses, the kind of which the brainstem/midbrain is responsible for. This might have repercussions into psychiatry and psychotherapy.

It's not unique to humans at all. They originally found the two types of brain cells by looking at mouse embryos. Then,

"Finally, the researchers looked back over 550 million years of evolutionary time. They found the same two-origin brain pattern in chickens; zebrafish; and, remarkably, in acorn worms, tiny creatures living on the ocean floor that share a distant common ancestor with humans. Jellyfish, which diverged from humans about 600 to 700 million years ago, have two nervous systems at different ends of their body.

“Our research suggests that evolution took two existing neural systems and pushed them together spatially,” Loh said. “Having the brain as one organ would probably be more efficient, but we rely on this primordial way to make the brain as two separate pieces.”

We've long known the forebrain, midbrain and hindbrain control different things, we just didn't know the hindbrain neuron cells evolved so fundamentally differently. Being able to grow the right kind in a lab will enable research that wasn't possible before.

*some other animals

That’s what I read. I thought it said mid- and fore- have the same gene expressions, whereas the hindbrain has a distinctly different gene expression and development.

They identified two different brain progenitor cells. One, which expresses a gene called Otx2, is destined to become the forebrain and midbrain. The other, which expresses a gene called Gbx2, is committed to forming the hindbrain.

And I think they mean the hindbrain, as in the brain stem and medulla oblongata, is one type of neuron, whereas the lobes — occipital, temporal, frontal, etc. — are another type.

Hindbrain and the lobes aren't neuron. Neither are they a type of neuron.
They have neurons. Of different types.

The article clearly delineates why instead of one organ, the brain is now considered as two separate organs. The forebrain and hind brain don't have the same progenitor cells. If they don't originate from the same cells, how can they be considered one organ? They are just right next to each other, like the gallbladder and the liver.