Sunday, November 4, 2018

Race, Brain Function, and Cortical Geometry

A remarkable hyper-confirmation of the biological basis of race.  In all cases, emphasis added.

Link to paper (including PDF).  Abstract, emphasis added:
Resting state functional magnetic resonance imaging (rs-fMRI) is a popular imaging modality for mapping the functional connectivity of the brain. Rs-fMRI is, just like other neuroimaging modalities, subject to a series of technical and subject level biases that change the inferred connectivity pattern. In this work we predicted genetic ancestry from rs-fMRI connectivity data at very high performance (area under the ROC curve of 0.93). Thereby, we demonstrated that genetic ancestry is encoded in the functional connectivity pattern of the brain at rest. Consequently, genetic ancestry constitutes a bias that should be accounted for in the analysis of rs-fMRI data.
This not only confirms a biological basis for race but does so in the most relevant and dramatic fashion possible: a scanning measurement of brain function is able to determine racial ancestry, correlated to genetics, in a highly accurate manner.  This is a “double win” for legitimate racial science: not only does it clearly demonstrate a biological basis for race, but shows that mental functioning at the physical (brain) level is correlated to genetically-determined racial identification, supporting hypotheses dealing with varying cognitive and behavioral mental characteristics associated with racial differences.

Here, we demonstrate that the three-dimensional geometry of cortical surface is highly predictive of individuals’ genetic ancestry in West Africa, Europe, East Asia, and America, even though their genetic background has been shaped by multiple waves of migratory and admixture events. The geometry of the cortical surface contains richer information about ancestry than the areal variability of the cortical surface, independent of total brain volumes. Besides explaining more ancestry variance than other brain imaging measurements, the 3D geometry of the cortical surface further characterizes distinct regional patterns in the folding and gyrification of the human brain associated with each ancestral lineage.

Human skull and brain morphology are strongly influenced by genetic factors, and skull size and shape vary worldwide. However, the relationship between specific brain morphology and genetically-determined ancestry is largely unknown.
We used two independent data sets to characterize variation in skull and brain morphology among individuals of European ancestry. The first data set is a historical sample of 1,170 male skulls with 37 shape measurements drawn from 27 European populations. The second data set includes 626 North American individuals of European ancestry participating in the Alzheimer's Disease Neuroimaging Initiative (ADNI) with magnetic resonance imaging, height and weight, neurological diagnosis, and genome-wide single nucleotide polymorphism (SNP) data.
We found that both skull and brain morphological variation exhibit a population-genetic fingerprint among individuals of European ancestry. This fingerprint shows a Northwest to Southeast gradient, is independent of body size, and involves frontotemporal cortical regions.
Our findings are consistent with prior evidence for gene flow in Europe due to historical population movements and indicate that genetic background should be considered in studies seeking to identify genes involved in human cortical development and neuropsychiatric disease.
More excerpts:
Furthermore, Ashkenazi Jewish individuals are geographically dispersed in Europe and yet are genetically quite similar and genetically intermediate between SE European and Middle Eastern populations…
Intracranial and brain volumes and cortical surface area progressively increase with the amount of inferred NW European ancestry (fig. 3 b), and these measures are approximately 5% larger in the 10% of individuals with the most NW European ancestry compared to the 10% with the most SE European ancestry. This percentage increase matches the percentage increase in cranial length and breadth observed along the same NW-SE geographic axis in the skull data set (fig. 2 b) and cannot be attributed to a correlation with body size since we controlled for height and weight. This correlation involves specific – not global – brain morphology because hippocampal, basal ganglia, ventricular, and cerebellar volumes and average cortical thickness are not associated with NW-SE ancestry.
Next, we performed both a region of interest analysis and vertex-based tests across the cortex to test whether the surface area of specific cortical regions showed more significant association with the degree of NW-SE ancestry. We found that cortical surface area predominantly in the frontal and temporal lobes from both hemispheres is significantly associated (online suppl. table S4) and is 4–9% larger among 10% of individuals with the most NW European ancestry compared to 10% with the most SE European ancestry. We found a similar frontotemporal pattern of association with the degree of NW-SE ancestry with a vertex-based analysis (fig. 4 ; online suppl. fig. S6).
One can speculate that these differences are derived from Paleolithic hunter-gatherer vs. Neolithic farmer ancestry percentages, with brain size and intelligence being maximized among northern hunter-gatherers.  Note that the frontal lobes are important in judgment and impulse control, and these data may explain the stereotypes of the restrained, disciplined, stoic Nordic vs. the gesticulating, undisciplined, emotional Swarthoid. Temporal lobes deal with sensory input, and size differences there may be related to the greater requirement for spatial competence in hunter-gatherers.

Race Is Real.
Race Has A Genetic, Biological Basis.
Racial Differences Are Associated With Variation In Brain Activity and Brain Structure