Neanderthals May Influence Rare Brain Disorder in Humans

Research suggests that Neanderthals, our extinct relatives who interbred with early humans, might have passed on DNA linked to a serious brain condition that can lead to fatal outcomes. This condition, called Chiari malformation type I, affects the lower area of the cerebellum, causing it to protrude through the skull into the spinal canal. Symptoms can include headaches, neck pain, and dizziness, and in extreme cases, it can be life-threatening.

In less severe instances, treatment may involve muscle relaxants, but for more serious cases, surgical procedures might be necessary. Dr. Mark Collard, a paleoanthropologist from Simon Fraser University, indicated that some patients may require removal of bone from the braincase or vertebrae to alleviate pressure.

First identified in the 1800s by the Austrian pathologist Hans Chiari, this disorder is estimated to affect 1 in 1,000 individuals. However, newer imaging studies imply it might actually be more common, possibly affecting more than 1 in 100 people, since many cases don’t present significant symptoms.

Chiari malformation type I occurs when the occipital bone at the back of the skull is too small to accommodate the brain, which can cause bulging that becomes pinched. The precise reasons for the unusually small occipital bone remain unclear.

A 2013 study argued that Neanderthal interbreeding with modern humans might contribute to this condition. It was found that non-Africans have about 1.5% to 2% Neanderthal DNA, hinting at the genetic influence of these ancient humans on modern populations.

Modern human skulls have a more rounded shape compared to the elongated skulls of Neanderthals. The 2013 study mentioned that the Neanderthal DNA could affect how contemporary humans develop skulls, potentially leading to a mismatch between brain size and skull shape, particularly at the base.

The recent research involved analyzing 3D CT scans of 103 living individuals—46 with Chiari malformation and 57 without. The team also compared these skulls with eight fossil skulls of our relatives, including Neanderthals. The findings showed that those with the malformation exhibited skull shapes more similar to Neanderthals than those without the condition.

Collard, who co-authored the study, remarked that this research brings us closer to understanding the causes of Chiari malformation type I. He emphasized the importance of pinpointing causal relationships in medicine, stating that clarity could enhance the management or even resolution of medical conditions.

However, he cautioned that while the findings are promising, they do not conclusively establish a link between this disorder and Neanderthal genetics. Scientific research typically requires more than just one study for definitive conclusions, he noted.

Looking ahead, further studies could analyze additional skulls, particularly fossilized ones. There’s also potential for exploring data from Africa, as existing knowledge suggests that Neanderthal DNA presence is higher in Europe and Asia than in Africa.

If future research does confirm a genetic connection between Neanderthals and this condition, integrating genetic screening into early childhood health checkups might be beneficial. This could help identify individuals at increased risk for developing Chiari malformation type I, allowing for better monitoring and care.

The findings were published on June 27 in the journal Evolution, Medicine, and Public Health.