Neanderthal DNA Linked to Modern Brain Malformations: Study

3D models of Homo sapiens (top two images) and Homo neanderthalensis (bottom two images) crania for visual comparison. The human model was created from DICOM files of an anonymized volunteer patient from the Manchester Centre for Clinical Neurosciences. The Neanderthal model is based on La Ferrassie 1 and was created by LB and TR. Credit: Evolution, Medicine, and Public Health (2025). DOI: 10.1093/emph/eoaf009

If you regularly experience headaches, dizziness, balance problems and blurred vision, our Neanderthal cousins could be to blame. These are common symptoms of Chiari malformations, structural defects in which the lower part of the brain extends into the spinal cord. People with this condition have skulls shaped like those of our ancient relatives, leading to a hypothesis (known as the Archaic Homo Introgression Hypothesis) that it may be a genetic legacy from interbreeding between modern humans and Neanderthals.

To investigate this, Kimberly Plomp of the University of the Philippines Diliman and colleagues zeroed in on Chiari 1, the mildest form of the condition, which affects around 1 in 100 people. The team built 3D models of the skulls of 46 living adults with the condition and 57 controls from hospital CT scans. Mathematical analysis revealed that the skulls of people with Chiari 1 have a smaller, flatter occipital bone, located at the back and base of the skull. There is also more brain compression at the base of the skull where the cerebellum sits. This structure plays a crucial role in balance and motor control.

The researchers then compared both sets of modern skulls with digital models of eight skulls from ancient Homo sapiens, Homo erectus, Homo heidelbergensis and Homo neanderthalensis. They found that the skull bases of the Chiari skulls closely matched those of Homo neanderthalensis while the bases of the control group more closely resembled those of modern humans.

While the results are fascinating, they are not conclusive. According to the Archaic Homo Introgression Hypothesis, individuals develop Chiari 1 because some of their cranial development-coding genes come from three extinct Homo species—Homo erectus, Homo heidelbergensis and Homo neanderthalensis. However, the study, published in the journal Evolution, Medicine, and Public Health, doesn't support this entirely.

Nevertheless, the research highlights how ancient DNA may be affecting our health today. Most people of non-African descent carry approximately 1–2% of Neanderthal DNA in their genome. The next stage for the University of the Philippines Diliman scientists will be to hunt for Neanderthal genes in the DNA of people with Chiari malformations. If these genes are identified, it could open the door to a better understanding of the condition's origins, as well as earlier diagnosis and more effective surgical intervention.

Written for you by our author Paul Arnold, edited by Gaby Clark, and fact-checked and reviewed by Robert Egan—this article is the result of careful human work. We rely on readers like you to keep independent science journalism alive. If this reporting matters to you, please consider a donation (especially monthly). You'll get an ad-free account as a thank-you.

More information: Kimberly Plomp et al, A test of the Archaic Homo Introgression Hypothesis for the Chiari malformation type I, Evolution, Medicine, and Public Health (2025). DOI: 10.1093/emph/eoaf009

According to the source: Phys.org.