Improved dating of the human/chimpanzee separation in the mitochondrial DNA tree: Heterogeneity among amino acid sites |
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Authors: | Jun Adachi Masami Hasegawa |
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Institution: | (1) Department of Statistical Science, The Graduate University for Advanced Studies, 4-6-7 Minami-Azabu, Minato-ku, 106 Tokyo, Japan;(2) The Institute of Statistical Mathematics, 4-6-7 Minami-Azabu, Minato-ku, 106 Tokyo, Japan |
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Abstract: | The internal branch lengths estimated by distance methods such as neighbor joining are shown to be biased to be short when the evolutionary rate differs among sites. The variable-invariable model for site heterogeneity fits the amino acid sequence data encoded by the mitochondrial DNA from Hominoidea remarkably well. By assuming the orangutan separation to be 13 or 16 Myr old, a maximum-likelihood analysis estimates a young date of 3.6 ± 0.6 or 4.4 ± 0.7 Myr (±1 SE) for the human/chimpanzee separation, and these estimates turn out to be robust against differences in the assumed model for amino acid substitutions. Although some uncertainties still exist in our estimates, this analysis suggests that humans separated from chimpanzees some 4–5 Myr ago.Correspondence to: M. Hasewaga |
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Keywords: | Mitochondrial DNA Hominoidea Molecular clock Maximum likelihood Site heterogeneity |
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