The intersection of anatomically modern Homo sapiens and Neanderthals thousands of years ago might contribute to Chiari malformation type 1, a serious neurological condition that affects an estimated 1% of today’s population.
In 2013, scientists surmised that Chiari malformation type 1 might arise from cranial development genes tracing back to three smaller extinct Homo species: Homo erectus, Homo heidelbergensis, and Homo neanderthalensis. Plomp et al. employed 3D data and geometric morphometry to evaluate this hypothesis. Image credit: Neanderthal Museum.
Chiari malformation type 1 occurs when the rear of the skull is insufficiently sized to accommodate the brain, causing a portion of the brain to protrude from the skull into the spinal canal.
This condition can compress the herniated brain tissue, resulting in symptoms such as headaches, neck pain, and dizziness. In severe instances, this can lead to life-threatening complications.
“In medicine, as in all sciences, clarifying the causal chain is vital.”
“The clearer the causal relationships, the greater the chances that the condition can be effectively managed or even resolved.”
“Further testing of the hypothesis is needed, but our study may bring us a step closer to understanding the causal chain that leads to Chiari malformation type 1.”
In 2010, genetic evidence emerged indicating that modern humans interbred with Neanderthals tens of thousands of years ago.
Individuals of non-African descent carry approximately 2-5% Neanderthal DNA, tracing back to these ancestral mating interactions.
The hypothesis suggesting that Chiari malformation type 1 may stem from ancient Homo genes entering the human gene pool through mating was first proposed by researcher Evens Barbosa Fernandez from the University of Campinas.
Dr. Fernandez hypothesized that the differences in skull structure between modern humans and other Homo species play a significant role in causing malformations.
In this study, Professor Mark Collado, PhD, Kimberly Promp at the University of the Philippines Diliman, and colleagues employed modern imaging techniques and advanced statistical shape analysis to compare 3D models of living humans with those of Homo sapiens, Neanderthals, Homo heidelbergensis, and Homo erectus.
The findings revealed that individuals with Chiari malformations exhibit more similar skull shapes to Neanderthals than those without such malformations.
Notably, all other fossil skulls align more closely with modern humans lacking Chiari malformation type 1, supporting the hypothesis that certain individuals today carry Neanderthal genes that influence skull shape, potentially leading to a mismatch between skull dimensions and the shape of the modern human brain.
This discrepancy could result in insufficient space within the skull, causing the brain to extend into the spinal cord, which is the only available outlet.
Given that various global populations possess different levels of Neanderthal DNA, this study suggests that certain European and Asian populations may be more susceptible to Chiari malformation type 1, although additional research is needed to validate this.
“The study of archaeology and human evolution is not merely fascinating,” Professor Collado remarked.
“It could offer insights into current health challenges.”
“In this instance, fossils have provided clarity about the condition, but numerous modern issues also help illuminate archaeological and paleontological findings.”
Study published in the journal Evolution, Medicine, Public Health.
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Kimberly Promp et al. 2025. An ancient hypothesis regarding Homo introduction and Chiari malformation type I Evolution, Medicine, Public Health 13(1):154-166; doi:10.1093/end/eoaf009
Source: www.sci.news
