Study finds human brain comprises two distinct evolutionary organs
Stanford Medicine researchers report that the forebrain and hindbrain develop from separate progenitor cells, redefining the brain as two independent organs and enabling new laboratory models.
Researchers at Stanford Medicine have presented evidence that the human brain consists of two separate organs that evolved independently. The study shows that the forebrain and midbrain arise from one type of progenitor cell, while the hindbrain develops from a different early cell lineage, contradicting the long-standing view of a single developmental origin.
The more primitive hindbrain controls essential autonomic functions such as breathing, heart rate and sleep, whereas the forebrain supports higher-order processes including language, abstract reasoning and creativity. "We've shown for the first time that the front of the brain arises from a totally different progenitor cell than the back of the brain," said Kyle Loh, PhD, associate professor of developmental biology.
The discovery allowed scientists to generate hindbrain neurons in vitro for the first time, a step that could accelerate research into brain-stem disorders. Co-first author Rayyan Jokhai noted that earlier attempts likely failed because they tried to coax forebrain and midbrain progenitors into hindbrain cells, which the new findings indicate is not feasible.
Comparative analysis across species revealed a similar two-origin pattern in chickens, zebrafish and acorn worms, suggesting the arrangement dates back more than 500 million years. "Our research suggests that evolution took two existing neural systems and pushed them together spatially," Loh added.
The findings reshape understanding of brain development and may open new avenues for studying neurological diseases.