Human brain evolved from 2 ancient nervous systems: Stanford study

A new study led by Stanford Medicine researchers has challenged the long-held understanding of how the human brain develops, finding that it originates from two distinct populations of early progenitor cells rather than a single developmental source.The researchers say their findings suggest that the human brain is essentially a composite structure formed from two ancient nervous systems that evolved independently and were eventually integrated into one organ. The study was published in Nature Neuroscience on September 18, 2026.For decades, scientists had followed a model in which a single early progenitor cell was thought to give rise to the entire brain.