Age of the DA and Xiao elements. Thin arrows indicate that Xiao and type I DA first emerged 25-18 Myr ago, whereas Type II/III DA emerged 14-7 Myr ago. Thick arrows indicate that the amplification peak of Xiao and DA occurred during 25-14 and 14-7 Myr ago, respectively. There are a total of 45 copies of Xiao, 2 copies of type I DA, 13 copies of type II DA, and 5 copies of Type III DA. The evolutionary tree of the primates is presented the same way as in Fig. 1.