Our Brains May Be Two Brains in One

Your brain may be more of a duet than a solo act. A new study in Nature Neuroscience suggests that the human brain is essentially two ancient nervous systems that evolved separately but now function as one tightly linked organ, reports the Telegraph. By tracking the earliest stages of brain formation in mouse embryos, the team found that the front (forebrain and midbrain, which handle thinking and decision-making) and the back (hindbrain or brain stem, which manages breathing, heartbeat, sleep, and swallowing) arise from entirely different progenitor cells that never overlap.

"Our research suggests that evolution took two existing neural systems and pushed them together spatially," says Stanford researcher Kyle Loh in a university release. "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." The work helps explain why scientists had long struggled to grow hindbrain cells in the lab, a hurdle in studying conditions like spinal muscular atrophy and ALS that damage brain-stem neurons. The findings will enable them to do so, says Loh, opening a path to better disease models and potential drug discovery. The pattern also shows up in simple sea creatures, suggesting this two-system setup has been around for about 500 million years.