"New research led by Stanford Medicine reveals that what we call the brain is two distinct organs that evolved independently over hundreds of millions of years," Stanford Medicine announced this week:
The new research finding shows that the human brain consists of two ancient nervous systems cleverly packaged together — a more primitive part that regulates our hearts' beating, our breathing and other functions, and another that makes us distinctly human, capable of poetry, mathematics and wondering about our own origins. The discovery could help explain why scientists have struggled for decades to grow certain types of brain cells in the laboratory — and it opens new avenues for studying devastating diseases that affect the brain stem...
[S]cientists have struggled for decades to generate human hindbrain neurons in the laboratory. This gap has hampered research into devastating diseases affecting the brain stem, including spinal muscular atrophy and amyotrophic lateral sclerosis... The researchers' breakthrough came from studying the earliest moments of embryonic development... [Study co-authors Carolyn Dundes and Rayyan Jokhai] discovered that the hindbrain follows a separate developmental path, running in parallel to — rather than branching off from — the pathway that creates the forebrain and midbrain... This revelation explained decades of frustration in the field — scientists had been trying to turn one type of progenitor cell into another that it is fundamentally incapable of becoming... Armed with this knowledge, the researchers for the first time successfully coaxed human pluripotent stem cells (a kind of cell that can create any cell in the human body) to become functional hindbrain motor neurons in the laboratory...
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."
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