Phylogenetic tree constructed by the neighbor-joining method showing the complete mitochondrial DNA (mtDNA) region (16,750 bp) of <i>Homo sapiens sapiens</i> and <i>Homo sapiens neanderthalensis</i> and suggesting the evolution of the Glu12 repeats.

<p>On the basis of the differences in Glu12 frequency in the three groups, it is likely that most ancestors of modern-day Africans primarily had Glu12 repeats of the α2B-AR gene, and not Glu9 repeats.