FIG. 1.—

The gene model for FOXP2, variation data for a modern human sample and genealogical cartoon. (a) A subset of the gene model (based on Ensembl 48) for FOXP2 showing exons 4–8 (tan boxes) with spliced-out introns in between. The region surveyed in Enard et al. (2002) is indicated by the red bar, below which are the polymorphic intronic sites (gray triangles) and the 2 human-specific amino acid substitutions in exon 7 (overlapping purple circle and green diamond). (b) Phased haplotypes from Enard et al. (2002), for the 9 sites with high-frequency–derived alleles in the extant human sample. Open red circles denote the ancestral variant, and closed red circles denote the derived variant. Ancestral haplotypes (white) are defined as those carrying the ancestral allele at one or more of the sites with high-frequency–derived alleles. Blue circles indicate the fixed amino acid substitutions. (c) A cartoon of the genealogical relationship between individuals in this region of FOXP2. A hypothetical genealogy (blue) at the selected site is superimposed on a genealogy (red) of a region linked to the selected site. At the selected site, all lineages coalesce rapidly because of the selective sweep. Recombination events (r) have occurred on some lineages of the red genealogy, bringing the selected allele onto additional ancestral backgrounds. The crosses on the genealogy indicate the mutation to the selected allele (blue) and 3 mutations leading to high-frequency–derived alleles (red). The resulting haplotypes are shown at the bottom of the figure. We estimate the tMRCA (t) of the selected haplotype by counting the average number of mutations on haplotypes carrying the high-frequency–derived alleles (this variation is not shown in the figure).