Median joining network of Clade I haplotypes. Solid ellipse highlights Clade Ia and dashed ellipse highlights the only extant haplotype inferred to be derived from an ancient American dog haplotype and that ancient haplotype. Node size is proportional to haplotype frequency. Transversal lines indicate mutations and black dots hypothetical haplotypes. Ancient American haplotypes are red, contemporary American haplotypes are yellow and contemporary dogs from elsewhere in the world are blue. Photograph inset: dog from Chan Kom (M76 in Table S1), a likely descendant of pre-Columbian native American dogs.