A phylogenetic comparison of the ψη-globin DNA sequence of the spider monkey (Ateles geoffroyi) to orthologous sequences from other primates provides evidence for an evolutionarily recent (<17 million years ago (MYA)) insertion of a truncated L1 LINE (long interspersed repetitive element). An Alu LINE (short interspersed element), found 3 kb downstream of the poly(A) addition site, arose <40 MYA subsequent to the divergence of platyrrhinies (New World monkeys) from catarrhines (humans, apes, and Old World monkeys). Another Alu element, which appears in the catarrhines 588 bp upstream from the ψη gene, is absent in Ateles, thus placing its possible time of insertion between 20 and 40 MYA. Alignment of the Ateles ψη sequence with orthologous hominoid sequences (M. M. Miyamoto, J. L. Slightom, and M. Goodman, 1987, Science 238: 369-373) provides unequivocal evidence against the view (J. H. Schwartz, 1987, "The Red Ape: Orang-utans and Human Origins," Houghton Mifflin, Boston, MA) that the orangutan forms a monophyletic group with human. Furthermore, a critical analysis of potential sources of homoplasy (i.e., parallel evolution) reaffirms a Homo-Pan monophyletic clade (Miyamoto et al., 1987). Reconstraction of primate ψη sequence phylogeny suggests Ateles and Aotus shared a common ancestor only 16 ± 1.5 MYA. Finally, the results show a mutation rate of 1.7 ± 0.2 × 10-9 mutations site-1 year-1 during the evolution of the Ateles ψη-globin region since the divergence of catarrhines from platyrrhinies. This rate is considerably slower than the average mammalian rate, but faster than that of the hominoids, supporting a primate (especially a hominid) mutation rate slowdown.
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