Scientists Discover the Human Brain May Develop From Two Separate Nervous Systems

Scientists have uncovered a surprising insight into how the human brain develops: rather than emerging from a single population of early cells, different regions of the brain appear to originate from two distinct groups of embryonic cells.

The research, led by scientists at Stanford Medicine and published in Nature Neuroscience on September 18, 2026, challenges a long-standing model of brain development. The findings suggest that the forebrain and midbrain develop from one group of progenitor cells, while the hindbrain follows a separate developmental pathway.

The discovery could have important implications for neuroscience, particularly for scientists trying to grow specific types of human brain cells in laboratories to study neurological diseases.

The Brain May Have Two Distinct Developmental Origins

For centuries, the brain has been understood as a single organ with interconnected regions that perform different functions. The new research does not change the fact that the adult brain functions as an integrated system. Instead, it challenges the idea that all its major regions originate from the same early population of embryonic cells.

Researchers identified two distinct groups of progenitor cells during early development.

One group, associated with the gene Otx2, gives rise to the forebrain and midbrain. These regions are involved in functions including higher-level thinking, sensory processing and movement.

The second group, associated with the gene Gbx2, develops into the hindbrain, which includes structures responsible for essential functions such as breathing, heartbeat regulation and aspects of swallowing and movement.

The two populations followed separate developmental pathways, suggesting that the brain is assembled from distinct cellular origins rather than growing from one common source.

How Scientists Made the Discovery

The research team investigated early development by studying mouse embryos and tracing the origins of different brain regions.

The scientists found that the two populations of progenitor cells emerged in parallel during a developmental stage called gastrulation. This is an early phase of embryonic development when cells begin organizing into the structures that will eventually form the body.

The researchers also examined chromatin, the material that packages DNA inside cells. They found differences in chromatin organization between the two populations, helping explain why each group follows a different developmental pathway.

These findings indicate that the cells become committed to producing different brain regions early in development.

The team also investigated whether the pattern might extend beyond humans and mice. Their evolutionary analysis found evidence consistent with separate developmental origins across several animal groups, suggesting that this arrangement may have ancient evolutionary roots.

A Breakthrough for Growing Brain Cells in the Laboratory

One of the most important practical outcomes of the study was the team’s ability to produce functional human hindbrain motor neurons from human pluripotent stem cells.

Pluripotent stem cells can develop into many different cell types under suitable conditions. However, researchers have historically struggled to generate certain specialized hindbrain neurons reliably in laboratory settings.

Understanding the distinct developmental origins of these cells gave the researchers a new approach. Instead of trying to direct cells through an inappropriate developmental pathway, they could guide them toward the correct lineage from an earlier stage.

The resulting motor neurons displayed electrical activity and molecular characteristics associated with authentic hindbrain cells.

This achievement could help researchers build more accurate laboratory models of the nervous system.

Why This Matters for ALS and Spinal Muscular Atrophy

The hindbrain contains neurons involved in controlling muscles needed for swallowing, facial movement and other essential functions. Some neurological disorders affect these cells, making them important targets for research.

Two conditions of particular interest are amyotrophic lateral sclerosis (ALS) and spinal muscular atrophy (SMA).

ALS is a progressive neurological disease that damages nerve cells responsible for controlling voluntary muscles. SMA is a genetic disorder that affects motor neurons and can cause severe muscle weakness.

Scientists need reliable laboratory models of the relevant human neurons to investigate how these diseases develop and to test potential treatments.

The new research could make it easier to produce specific hindbrain neurons for such studies. However, the findings do not mean that either disease has been cured or that a new treatment is ready for patients.

Further research will be needed to determine how these laboratory-grown cells can contribute to understanding disease mechanisms and evaluating therapies.

What the Discovery Means for Our Understanding of Evolution

The research also raises questions about how the brain evolved.

The scientists found evidence suggesting that the two-origin developmental pattern may have been conserved across hundreds of millions of years of evolution. Their analysis included several vertebrate species and more distantly related animals.

This does not mean that the brains of these animals are identical. Instead, the findings suggest that some basic features of nervous-system development may have ancient evolutionary roots.

Understanding these shared developmental mechanisms could help scientists investigate how complex nervous systems evolved and how different brain regions acquired their specialized functions.

What Happens Next?

The next challenge is to determine how these findings can improve research into human brain development and neurological disorders.

Scientists will need to refine methods for producing specialized neurons, test how accurately laboratory-grown cells reproduce the behavior of cells inside the human body, and investigate how these models can be used to study disease.

The research offers a new way to think about the developmental origins of the brain. More importantly, it provides a practical approach for growing cell types that have been difficult to produce in the laboratory.

The discovery is not evidence that humans literally possess two independent brains. Rather, it suggests that the brain’s major regions emerge from distinct embryonic cell populations before becoming parts of one integrated organ.

Frequently Asked Questions (FAQ)

1. Did scientists discover that humans have two brains?

No. The study suggests that major brain regions develop from two distinct populations of embryonic cells. The adult brain remains one integrated organ.

2. Which parts of the brain develop from the two cell populations?

One population gives rise to the forebrain and midbrain, while another produces the hindbrain.

3. What are Otx2 and Gbx2?

They are genes associated with the two different developmental cell populations identified in the study. Otx2 is associated with forebrain and midbrain development, while Gbx2 is associated with hindbrain development.

4. Why is growing hindbrain neurons in the laboratory important?

It could help scientists study the development and function of specific human neurons and create better laboratory models for investigating neurological diseases.

5. Could this research lead to treatments for ALS or spinal muscular atrophy?

The research may support future studies of these conditions, but it does not provide a treatment or cure. Further research is needed to establish its medical applications.

6. When was the study published?

The study was published in Nature Neuroscience on September 18, 2026.

7. Does this discovery change everything scientists know about the brain?

It challenges an established model of how the brain develops. It does not overturn the evidence that the adult brain functions as an interconnected organ.