Whiten et al. imply that we undervalued extant species. We find this perplexing. We never stated that studies of extant chimpanzees are unimportant. Our conclusions were based on intensive review of homologous anatomical traits in other primates. Indeed, to understand hominid origins, we must now instead rely on “fundamental evolutionary theory,” which Whiten et al. refer to as “strategic modeling.” Increasingly relevant is a vast and still growing knowledge of ecological, locomotor, social, and reproductive interrelationships of not just chimpanzees, but other primates and a wide variety of other vertebrates. In fact, using “data on extant species…to derive general principles” was exactly our approach—the majority of the 108 citations in the final Ardipithecus paper referenced such studies. We expressly advocated more intensive reliance on additional living species (beyond Pan ) because these promise a more comprehensive understanding of social structure in advanced K primates (e.g., Brachyteles and other atelines), creation and use of tools (e.g., Cebus ), and even neuroendocrinology (voles and several primates). A broad comparative base is equally imperative for accurate phylogenetic analyses, particularly those involving cladistics. The potential of the latter methods to accurately “recover” ancestral phenotypes by parsimony relies on the presence and density of taxa (both extinct and extant) surrounding the nodes of interest. This has been empirically shown with morphological data sets ([ 1 ][1]) and certainly also applies to behaviors. For example, cladistic analysis of extant species may retrieve the locomotor behavioral trait of knuckle-walking, as the nodal phenotype for the Pan/Homo common ancestor, but the Ardipithecus forelimb shows that this inference is simplistic and almost certainly incorrect. Indeed, Ardipithecus and other Miocene hominoids establish that extant chimpanzees are poor models for our last common ancestor with chimpanzees. Contrary to Whiten et al. 's assertions, this conclusion was informed, and should be further extended, by general principles established from all relevant species. All great ape species merit study and conservation, but despite their genomic proximity, none of them should be interpreted as anatomically or behaviorally “living fossils” or “time machines.” 1. [↵][2] 1. D. S. Strait, 2. F. E. Grine , J. Hum. Evol. 47, 399 (2004). [OpenUrl][3][CrossRef][4][PubMed][5][Web of Science][6] [1]: #ref-1 [2]: #xref-ref-1-1 View reference 1 in text [3]: {openurl}?query=rft.jtitle%253DJournal%2Bof%2BHuman%2BEvolution%26rft.stitle%253DJournal%2Bof%2BHuman%2BEvolution%26rft.aulast%253DStrait%26rft.auinit1%253DD.%2BS.%26rft.volume%253D47%26rft.issue%253D6%26rft.spage%253D399%26rft.epage%253D452%26rft.atitle%253DInferring%2Bhominoid%2Band%2Bearly%2Bhominid%2Bphylogeny%2Busing%2Bcraniodental%2Bcharacters%253A%2Bthe%2Brole%2Bof%2Bfossil%2Btaxa.%26rft_id%253Dinfo%253Adoi%252F10.1016%252Fj.jhevol.2004.08.008%26rft_id%253Dinfo%253Apmid%252F15566946%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [4]: /lookup/external-ref?access_num=10.1016/j.jhevol.2004.08.008&link_type=DOI [5]: /lookup/external-ref?access_num=15566946&link_type=MED&atom=%2Fsci%2F327%2F5964%2F410.2.atom [6]: /lookup/external-ref?access_num=000227253500002&link_type=ISI