Figure 3.

Evolutionary impact of Alu elements in primates. An approximate evolutionary tree is shown for various primate species. The approximate density of Alu elements in the genomes of those species is shown as the number of Alu elements per megabase (MB). For specific evolutionary time periods, marked by thicker lines, the number of lineage-specific Alu insertions (Lsi) is marked. Data of Alu/Alu recombination causing deletions (Dels) between the human and chimp genomes are also shown. Note that the rate of Alu insertion, as well as recombination, seems to vary with different lineages and different evolutionary time periods.