Sequence divergence of 2p11 duplicons. The graph compares the average divergence (substitutions per site, Kimura two-parameter model with standard error measurements) for baboon and all human duplicate copies (circles) to the average divergence for the human ancestral locus to all human pericentromeric copies (triangles). The former provides a locus-specific estimate of the effective number of substitutions since the divergence of Old World monkeys and human lineages (∼23 Mya), while the latter provides an estimate of the timing of the initial duplication event. With the exception of LSP1, the baboon copy corresponds to a single (nonduplicated) locus. The data are consistent with an initial duplicative transposition of the ancestral locus for all loci after separation of the Old World and human lineages. No duplications from an ancestral locus are observed within this 700-kb region which show <0.03 substitutions/per site. This suggests a cessation of euchromatic colonization of this region ∼10 Mya.
