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Scientists say the human brain has two separate beginnings

Qurexa Editorial Team21 September 20265 min read 0 0
Scientists say the human brain has two separate beginnings

What happened

On 18 September 2026, a research team led by Stanford Medicine published a paper in Nature Neuroscience with an unusual claim: the human brain is not one organ that grew bigger over time. It is two, built from two completely separate starting points, pushed together by evolution. The senior author was Kyle Loh, an associate professor of developmental biology at Stanford. The co-first authors were graduate students Carolyn Dundes and Rayyan Jokhai. The team studied mouse embryos at a very early stage of development, before anything recognisable as a brain exists. They found two separate groups of parent cells — the technical word is progenitor cells. One group switches on a gene called Otx2 and goes on to build the front and middle of the brain. The other switches on a gene called Gbx2 and builds the back of the brain, the hindbrain. The striking part is that these two groups never mix. They do not overlap and they do not swap roles. The DNA inside them is even packaged differently, which locks each group onto its own path from very early on. As Loh put it: "We've shown for the first time that the front of the brain arises from a totally different progenitor cell than the back."

Why this matters

The team did not stop at mice. They looked for the same two-origin pattern in chickens, zebrafish, acorn worms — small creatures that live on the sea floor — and jellyfish. They found it. That is what turns a curiosity about mouse embryos into a claim about evolution. If the same split shows up across animals that last shared an ancestor hundreds of millions of years ago, the split is very old indeed. The picture that emerges is that two ancient nervous systems, which evolved separately, were eventually brought together into one head. One of them runs the machinery that keeps you alive without you thinking about it — your heartbeat, your breathing. The other does the things we think of as most human: language, mathematics, wondering where we came from. If that is right, textbook diagrams of the brain as a single structure that simply grew more complex are telling only half the story.

What the evidence actually says

It is worth separating the solid part of this from the headline-friendly part. The solid part is the cell biology. Two distinct progenitor populations, marked by two different genes, with different chromatin packaging — that is a concrete, measurable finding in developing embryos. It is the kind of result other labs can check. The part that requires more care is the phrase "two separate organs". That is a way of describing what the cells do, not a claim that you have two brains rattling around in your skull. The front and back of your brain are wired together and work together every second of the day. What the study says is that they were built from different starting materials. Most of the detailed developmental work was done in animals, not humans. That is normal and necessary — you cannot study human embryos at this stage — but it means the human part of the story rests on the pattern holding across species, plus the laboratory work described below. And this is where it becomes genuinely practical. Having worked out what makes a hindbrain cell a hindbrain cell, the team coaxed human pluripotent stem cells into becoming working hindbrain motor neurons. These were not rough approximations: they carried the right proteins and produced real electrical activity. That is the useful outcome. Growing genuine human hindbrain neurons in a dish gives researchers something to study for conditions that attack exactly those cells — spinal muscular atrophy and motor neurone disease among them — and for the hindbrain circuits involved in hunger. None of that is a treatment. It is a better tool for the people looking for one, which is usually how treatments start.

Practical advice

There is nothing here to do differently tomorrow, and it would be dishonest to pretend otherwise. But there are a couple of things worth taking from it. Be patient with the gap between discovery and treatment. Lab-grown motor neurons are a research tool. Families living with motor neurone disease or spinal muscular atrophy have seen many promising headlines. This one is real progress, and it is progress at the earliest stage. Treat 'two separate organs' as shorthand. When a finding is summarised in five words, the five words usually oversell it. The careful version — the front and back of the brain grow from different cells — is just as interesting and actually accurate. If you want reliable information on a specific neurological condition, go to a charity. Organisations like the MND Association publish plain-English summaries of new research and are honest about what is still a long way off. Basic research pays off slowly. Nobody set out to grow hindbrain neurons. They set out to understand how an embryo builds a brain, and the tool fell out of the answer.

What to know

A Stanford-led team, publishing in Nature Neuroscience on 18 September 2026, showed that the front and the back of the brain grow from two completely separate populations of parent cells, marked by the genes Otx2 and Gbx2. The two never mix. The same split appears in mice, chickens, zebrafish, acorn worms and jellyfish, which suggests it is hundreds of millions of years old. Using that knowledge, the researchers grew genuine human hindbrain motor neurons from stem cells in the laboratory — cells that could help in studying spinal muscular atrophy, motor neurone disease and the brain circuits that control hunger. It changes how the brain's origins are taught. It does not change anyone's treatment yet. Sources: Stanford Medicine, 'Human brain is two separate organs, Stanford Medicine-led research finds', 18 September 2026, https://med.stanford.edu/news/all-news/2026/09/two-separate-brains.html; Medical Xpress, 'Human brain has a split origin, new research suggests', 18 September 2026, https://medicalxpress.com/news/2026-09-human-brain.html This article is for general information and does not replace advice from a doctor, pharmacist or other qualified healthcare professional.

#neuroscience#stem cells#evolution#brain#research#Nature Neuroscience

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