Genomic data support the hominoid slowdown and an Early Oligocene estimate for the hominoid–cercopithecoid divergence
- Departments of †Anthropology and ∥Biological Sciences, Hunter College of the City University of New York, 695 Park Avenue, New York, NY 10021; and ¶Department of Cell Biology and Anatomy, University of Calgary, Calgary, AB, Canada T2N 4N1
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Edited by David Pilbeam, Harvard University, Cambridge, MA, and approved October 27, 2004 (received for review September 30, 2004)
Abstract
Several lines of indirect evidence suggest that hominoids (apes and humans) and cercopithecoids (Old World monkeys) diverged around 23–25 Mya. Importantly, although this range of dates has been used as both an initial assumption and as a confirmation of results in many molecular-clock analyses, it has not been critically assessed on its own merits. In this article we test the robusticity of the 23- to 25-Mya estimate with ≈150,000 base pairs of orthologous DNA sequence data from two cercopithecoids and two hominoids by using quartet analysis. This method is an improvement over other estimates of the hominoid–cercopithecoid divergence because it incorporates two calibration points, one each within cercopithecoids and hominoids, and tests for a statistically appropriate model of molecular evolution. Most comparisons reject rate constancy in favor of a model incorporating two rates of evolution, supporting the “hominoid slowdown” hypothesis. By using this model of molecular evolution, the hominoid–cercopithecoid divergence is estimated to range from 29.2 to 34.5 Mya, significantly older than most previous analyses. Hominoid–cercopithecoid divergence dates of 23–25 Mya fall outside of the confidence intervals estimated, suggesting that as much as one-third of ape evolution has not been paleontologically sampled. Identifying stem cercopithecoids or hominoids from this period will be difficult because derived features that define crown catarrhines need not be present in early members of these lineages. More sites that sample primate habitats from the Oligocene of Africa are needed to better understand early ape and Old World monkey evolution.
Footnotes
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↵ § To whom correspondence should be addressed. E-mail: msteiper{at}hunter.cuny.edu.
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↵ ‡ M.E.S. and N.M.Y. contributed equally to this work.
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Author contributions: M.E.S. and N.M.Y. designed research; M.E.S., N.M.Y., and T.Y.S. performed research; M.E.S., N.M.Y., and T.Y.S. analyzed data; and M.E.S. and N.M.Y. wrote the paper.
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This paper was submitted directly (Track II) to the PNAS office.
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Abbreviation: Mya, million years ago.
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↵ †† Delson, E. (1996) in Abstracts, International Symposium: Evolution of Asian Primates (Primate Research Institute, Inuyama, Japan), p. 40.
- Copyright © 2004, The National Academy of Sciences
