SRGAP2 is involved in neuronal migration and differentiation, and plays a key role in synaptic development, brain mass and the number of cortical neurons. Differences at the level of variants within genes (Tajima's D, π, etc.). Most paralogs have negative Tajima's D values indicating purifying selection. For example, SRGAP2C has a very negative D (~-2.32) in the African population, suggesting recent emergence and positive selection for variants in this gene. Similarly, GPR89A (ancestor of GPR89B) has an extreme negative D (<5th percentile) in Africans and Americans, indicating strong conservation of function. The exception is a balancing selection signal in the CD8B gene. In the European and American populations, Tajima's D statistic for the CD8B region is high - reaching ~2.66 (highlighting the predominance of intermediate frequency alleles) - while in the African population, D≈0.62. This was investigated using the Kolmogorov-Smirnov test for difference in allele distributions: the p-value was p≈2.2×10^-16, confirming a significant difference in haplotypes between Africans and Europeans/Americans in this region. Such dissimilarity suggests that CD8B is subject to different selection pressures in populations (probably balancing in non-Africans).