(C) Daily Kos This story was originally published by Daily Kos and is unaltered. . . . . . . . . . . Top Comments: Not One Brain, But Two [1] ['Side Pocket', 'Blue Choir Singer', 'Liberal Thinking'] Date: 2026-09-20 Uploaded to DailyKos by Ed Tracey Here at Top Comments we strive to nourish community by rounding up some of the site’s best, funniest, most informative commentary, and we depend on your help!! Here’s how to submit nominations in DK6: If you see a comment by another Kossack that deserves wider recognition, please send it either to topcomments at gmail dot com or via kosmail to topcomments- either search for user @topcomments, or click that link then click “send message”!) by 9:30pm Eastern for inclusion in that day’s diary. Please, please include a few words about why you sent it in as well as your user name (even if you think we know it already :-)), so we can credit you with the find! It’s especially helpful if you include a link to the comment you’re nominating… hover over the comment and you’ll see Share and Report options. Click Share, then choose ”copy url” and paste that into your message to us. Scientists that study the brain have broadly classified three regions of the human brain into three regions: The forebrain, which mainly consists of the cerebral cortex, in which conscious thought is believed to take place, and where commands for voluntary movement of the various parts of the body originate. Then there’s the midbrain, consisting of the thalamus, hypothalamus, hippocampus, amygdala, and other brain regions located immediately below the cerebral cortex, which are the origins of emotions. Below the midbrain lies the hindbrain, consisting of the cerebellum and the brain stem, which control muscular coordination and involuntary actions, such as breathing and swallowing. [Note that this division of functions in the brain is only a rough guide, and the roles described here occasionally cross lines from one brain region to another.] For many years, scientists have thought that all parts of the brain originate from a single type of progenitor cell, but attempts to produce hindbrain cells from that cell type always failed. Now, scientists at Stanford Medical School have announced that they discovered the hindbrain in fact has a progenitor cell that is different from the previously known one, which implies that the modern vertebrate brain is the union of what were once two separate nervous systems. Hindbrain cells are necessary to be able to study certain neurological diseases, such as amyotrophic lateral sclerosis (ALS, also called Lou Gehrig’s disease), and spinal muscular atrophy (SMA), which is a leading cause of death among infants before their first birthday. Both of these diseases affect the entire brain, but the effects that cause death come from the damage they do to the hindbrain. The inability to swallow can result in pneumonia, as liquids meant to be swallowed end up in the lungs instead, and eventually, patients with these diseases cease breathing. Finding successful treatments for these diseases requires being able to study hindbrain neurons, yet it was not possible to grow such cell before discovering they originated from a cell type different from the rest of the brain. The team then examined the DNA packaging, or chromatin, in these [two types of] cells. Chromatin is a way cells determine which genes can be easily accessed and which are bundled away out of reach. What they found was striking: The anterior neural ectoderm (future forebrain and midbrain) and posterior neural ectoderm (future hindbrain) have fundamentally different chromatin configurations. These differences essentially locked each progenitor cell into its respective fate, like travelers on parallel tracks that never cross. “Previous attempts to make hindbrain neurons likely tried to coax forebrain and midbrain progenitors into hindbrain cells, which our study shows is not possible,” Jokhai said. The scientists also studied the brains of other organisms in an attempt to find when the two primitive nervous systems combined into one. 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, acorn worms, tiny creatures living on the ocean floor that share a distant common ancestor with humans. Jellyfish, which diverged from humans about 600–700 million years ago, have two nervous systems at different ends of their bodies. … “I was surprised at our findings because the word ‘brain’ implies a contiguous organ that likely has a singular origin,” Jokhai said. “But even 500 million years ago, there were these separate neural systems, which now almost operate as one, which is very cool.” As such, the discovery of the second progenitor brain cell type, for the hindbrain, provides two great benefits. First, it now makes possible the study of ways to treat and possibly cure fatal diseases of the hind brain, but it has also illuminated the origin of our own brains as a fusion of two neural systems when pre-vertebrates were still in the process of evolving. Now I guess I have to reevaluate that old Steve Martin movie The Man with Two Brains. 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