Abstract
Before their disappearance from the fossil record approximately 40,000 years ago, Neanderthals, the ancient hominin lineage most closely related to modern humans, interbred with ancestors of present-day humans. The legacy of this gene flow persists through Neanderthal-derived variants that survive in modern human DNA; however, the neural implications of this inheritance are uncertain. Here, using MRI in a large cohort of healthy individuals of European-descent, we show that the amount of Neanderthal-originating polymorphism carried in living humans is related to cranial and brain morphology. First, as a validation of our approach, we demonstrate that a greater load of Neanderthal-derived genetic variants (higher “NeanderScore”) is associated with skull shapes resembling those of known Neanderthal cranial remains, particularly in occipital and parietal bones. Next, we demonstrate convergent NeanderScore-related findings in the brain (measured by gray- and white-matter volume, sulcal depth, and gyrification index) that localize to the visual cortex and intraparietal sulcus. This work provides insights into ancestral human neurobiology and suggests that Neanderthal-derived genetic variation is neurologically functional in the contemporary population.
Highlights
If these alleles are biologically meaningful for their modern bearers[5], and by extension, for their extinct originators, individuals endowed with greater proportions of Neanderthal-derived sequence differences might be expected to harbor Neanderthal-like phenotypes
As the high coverage Altai Neanderthal draft sequence was used as the Neanderthal genotypes for each single nucleotide polymorphisms (SNPs), we examined the subset of 715 SNPs overlapping with the exome data publically available and previously reported for the Vindija and El Sidron Neanderthal samples[18], as well as for a Denisovan sample, to determine the degree these SNPs are specific to Neanderthals and maintained in other archaic samples
We found that NeanderScore positively correlated with an increase in sulcal depth in the right intraparietal sulcus (IPS; Tmax = 4.03, pcluster < 0.001, family-wise error (FWE)-corrected), directly beneath the area of maximal change in the prior skull shape analysis (Fig. 2), suggesting a significant but regionally circumscribed impact of Neanderthal genetic load on modern human brain
Summary
If these alleles are biologically meaningful for their modern bearers[5], and by extension, for their extinct originators, individuals endowed with greater proportions of Neanderthal-derived sequence differences might be expected to harbor Neanderthal-like phenotypes. To test this hypothesis, rather than using an additive model in a genetic association analysis, we performed linear regressions of polygenic measures of Neanderthal-derived common variant data with MRI imaging data. We further hypothesized that the morphometry of brain regions underlying the identified NeanderScore-associated cranial regions would be associated with Neanderthal genetic load
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