a, An SNP hotspot for KB1 and J. Watson on chromosome 17; both individuals are heterozygous for the 17q21.3 H2 haplotype. On either side are repetitive regions where SNPs cannot be called (grey). Local SNP rates are divided by the individual’s autosome-wide rate, so the expected rates are 1.0 (horizontal dotted line). KB1 has a nearly 2.5-fold enrichment of SNPs for 650,000 bases. b, Distribution of SNPs from Bushmen genomes (red line) and non-Bushmen genomes (black line), compared with nucleosome positions (filled grey plot), indicating the nucleosome-free region (NFR) and the –1 and +1 nucleosomes. TSS, transcription start site.