The phylogeny of the hominoid primates: a statistical analysis of the DNA-DNA hybridization data

Sibley and Ahlquist compared the single-copy nuclear DNA sequences of thehominoid primates using DNA-DNA hybridization. From this data set theyestimated a phylogeny that clusters man and chimpanzees using a distanceWagner procedure. However, no assessment of statistical confidence in thisestimated phylogeny was made, despite the fact that their data set containsinternal inconsistencies concerning the correct branching order. This paperpresents a modification of Pielou's Q- statistic that allows one to makenonparametric tests of phylogenetic relationship from distance data. Theresults of this analysis indicate that the estimated phylogeny of Sibleyand Ahlquist is without statistical significance owing to the internalinconsistencies of the data set. A survey and additional analyses of othertypes of molecular data indicate that the phylogeny that clusterschimpanzees and gorillas and has the human lineage splitting off earlier isstatistically consistent with all the molecular data (including the DNA-DNAhybridization data), whereas the phylogeny estimated by Sibley and Ahlquistcan be rejected at the 5% level using the data on restriction- endonucleasesites in the mitochondrial genome.