Examination of the fossil record suggests that Neanderthals, a sub-species of homo sapiens, or a distinct species with a common African ancestor called Homo Neanderthalensis, lived in Eurasia approximately 200,000 to 300,000 years ago during the Pleistocene Epoch. Many scientists have theorized that Neanderthals cohabited the Eurasian land mass with modern humans and thus interbred. Accordingly, Neanderthal-derived variants survive today in the modern human genome, yet the neural implications of this heritance have remained unclear—until now.
Using imaging studies, Gregory and colleagues have produced the first direct evidence that parts of the modern human brain from European decedents carry Neanderthal-derived polymorphism related to cranial and brain morphology, particularly in occipital and parietal bones. The extent of this polymorphism observed in modern humans is related to the amount Neanderthal DNA (NeanderScore) within the individual. NeanderScore-related findings included differences in gray and white-matter volume, sulcal depth, and gyrification index, that localize to the visual cortex and intraparietal sulcus. Concurrent research by Sasabayashi, et al. (2017), has demonstrated that cortical thickness and surface morphology in children and adolescents with schizophrenia were distinctly different from healthy controls.
Why Does This Matter?
These differences may reflect aberrations in cerebral and subcortical connectivity and may hold clues to understanding differences between current humans – from muscle mass to sleep to aggression to psychopathology, including deficits observed in schizophrenia and autism-related disorders.
Gregory’s team is currently investigating the pivotal role of this genetic variation in shaping the insula and related social brain circuitry. If a preclinical genetic marker can be identified for some forms of mental illness, particularly schizophrenia, then perhaps preclinical interventions can be investigated and developed.