Abnormalities in the skull that compress the lower brain can lead to headaches and various neurological issues, potentially passed down from Neanderthals.

Individuals with Chiari malformations possess a smaller, flatter skull base near the spine junction, causing the cerebellum to be pressed into the neck’s spinal canal.

Type 1 Chiari malformations, which are the least severe, may impact about 1 in 100 individuals. Symptoms can include headaches, neck pain, sleep apnea, and numbness, although some may remain asymptomatic.

Approximately 15 years ago, Yvens Barbosa Fernandes, a neurosurgeon at Campinas State University in Brazil, observed that the skull base of his Chiari patients bore resemblance to Neanderthal specimens from the European Museum, particularly the gentle slopes of the occipital bone where the cerebellum rests. Neanderthals had larger brains than modern humans, yet their skulls were more oblique at the foreheads and bases, resulting in a flatter shape compared to the rounder modern human skulls.

In 2013, Barbosa Fernandes published his hypothesis, suggesting that the shape of Chiari skulls could have a genetic link to an extinct human species, Homo sapiens. “In Chiari’s case, I began to consider a lost connection between anthropology and medicine,” he stated.

Motivated by this theory, Kimberly Plomp from the University of the Philippines in Quezon City and her team created digital 3D models of 46 Chiari 1 skulls and 57 unaffected skulls using CT scans. Their comprehensive mathematical analysis confirmed that the Chiari-affected skulls exhibited more cerebral compression at a flat angle at the base where the cerebellum is located.

Subsequently, the group compared these recent skulls with digital models of eight fossilized heads from Homo Neanderthalensis, Homo Erectus, Homo Heidelbergensis, and ancient Homo sapiens.

They discovered that the skull base measurements of Neanderthal heads closely matched those of modern humans with Chiari, while the skull bases of all other ancient species resembled typical modern humans without Chiari. “This underscores the notion that these modern humans may share Neanderthal characteristics,” suggesting another way Neanderthal genes could influence our health.

For Barbosa Fernandes, this research offers solid backing for his hypothesis. “It makes sense; a less pronounced angle results in less space for the modern human brain,” he noted. “Until now, I lacked scientific evidence to support my theory. This research brings me significantly closer to that proof.”

Looking ahead, the team intends to analyze the DNA of individuals with Chiari malformations in search of Neanderthal genetic markers, according to Plomp.

Other Chiari malformations (types 2-4) are believed to stem from various causes. Type 2 is associated with severe forms of spina bifida, while types 3 and 4 are exceedingly rare and can pose life-threatening risks.