The left/right brain thing has always been bunk. People have entire hemispheres removed with minimal negative consequences, personality changes, etc.

Probably three brains if you consider the neural activity going on in the gut and how it interacts with our brain.

In a study published in 2023, the scientists found that long COVID is associated with a reduction in the body's natural levels of serotonin, a signaling molecule that is produced the brain and the gut. In the brain, serotonin influences mood, sleep and memory. In the rest of the body, it plays a role in physiology, but Thaiss and Levy found that gut-produced serotonin can affect the brain as well.

....

Before these findings, scientists debated how SARS-CoV-2 could cause cognitive problems, as it is unclear if the virus breaches the blood-brain barrier. But the study by Thaiss and Levy suggests that the disease could have direct influence on the brain via the vagus nerve, regardless of whether the virus enters the brain.

...

The gut also contains the largest number of neurons outside the brain of any structure in the body — more than 100 million neurons line the human digestive tract, from the esophagus to the anus. These cells make up what is known as the enteric nervous system, which some scientists refer to as a "second brain."

It never ceases to amaze me how complicated our bodies and our minds are.

We're pretty good at using the lizard brain, actually.

One is a genius, the other's insane.

Are you thinking what I'm thinking?....

The meat does the thinking!

https://youtube.com/watch?v=5usXhX0zaO4

As long as one of them is only using lizard vocalizations it's completely normal.

It's that the brain stem is made of different cells than the forebrain and midbrain. You can't grow a full brain from one sample of cells. So, it's considered 2 different organs.

To expand on what frongt said. An organ is a collection of specialized tissues that performs certain specific tasks. The stomach is an organ, the pancreus is an organ, and together they are part of a system. If the brain is more than one organ, we can target specific parts in the tissue differences for lab cell growth (as the article suggests), targeted medicine delivery (due to differences in autonomic braincell makup vs frontal and temporal processing tissues), and the next step in research will probably be how the two brain organs develop connections which could lead to nerve pathway repair (typically very hard to achieve).

They don't fuse. They're connected, yes, but so is everything in your body.

Look up the split brain experiments. They’re incredibly interesting.