🌅 The Brain Is a Composite Organ with Two Origins

SOURCE

Jokhai et al. (2026)

WHAT TO KNOW

• A new study by researchers at Stanford Medicine found the brain arises from two separate types of embryonic cells—called progenitors—that split during the earliest stages of development and never overlap, one leading to the development of the forebrain and midbrain, and another going on to form the hindbrain. The finding suggests the brain is a composite organ made of two neural systems packaged together as one (not two distinct organs, as many media reports, including the study’s own press release, have incorrectly stated), upending the prevailing theory that the brain has a singular origin.

WHY IT MATTERS

• Adult brains have three main regions: the forebrain, midbrain, and hindbrain. The forebrain, the largest and most highly developed region, handles most of our high-level reasoning and thinking, while the hindbrain, which forms most of the brain stem, controls the body’s vital functions, like breathing, heart rate, and the muscles used for speech and swallowing. The midbrain forms the uppermost part of the brain stem and controls some reflexive actions and eye movement. The present study suggests the different regions arise from two separate progenitors that formed distinct neural systems which hundreds of millions of years of evolution eventually pushed together.

CONNECT THE DOTS

• Despite the importance of hindbrain cells, researchers have struggled to grow them in laboratory settings, making devastating diseases affecting the brain stem, like amyotrophic lateral sclerosis (ALS) and spinal muscular atrophy (SMA), notoriously difficult to study. In what appears to be a significant breakthrough, the authors of the present study successfully encouraged human stem cells to develop into hindbrain neurons, complete with electrical signals and characteristic proteins. The work should assist future research into both ALS, known to “rob people of the ability to walk, talk, and eventually breathe,” and SMA, the leading genetic cause of death in infants and toddlers.