title: The evolutionary relationships and age of Homo naledi: An assessment using dated Bayesian phylogenetic methods.
abstract: Homo naledi is a recently discovered species of fossil hominin from South Africa. A considerable amount is already known about H. naledi but some important questions remain unanswered. Here we report a study that addressed two of them: "Where does H. naledi fit in the hominin evolutionary tree?" and "How old is it?" We used a large supermatrix of craniodental characters for both early and late hominin species and Bayesian phylogenetic techniques to carry out three analyses. First, we performed a dated Bayesian analysis to generate estimates of the evolutionary relationships of fossil hominins including H. naledi. Then we employed Bayes factor tests to compare the strength of support for hypotheses about the relationships of H. naledi suggested by the best-estimate trees. Lastly, we carried out a resampling analysis to assess the accuracy of the age estimate for H. naledi yielded by the dated Bayesian analysis. The analyses strongly supported the hypothesis that H. naledi forms a clade with the other Homo species and Australopithecus sediba. The analyses were more ambiguous regarding the position of H. naledi within the (Homo, Au. sediba) clade. A number of hypotheses were rejected, but several others were not. Based on the available craniodental data, Homo antecessor, Asian Homo erectus, Homo habilis, Homo floresiensis, Homo sapiens, and Au. sediba could all be the sister taxon of H. naledi. According to the dated Bayesian analysis, the most likely age for H. naledi is 912 ka. This age estimate was supported by the resampling analysis. Our findings have a number of implications. Most notably, they support the assignment of the new specimens to Homo, cast doubt on the claim that H. naledi is simply a variant of H. erectus, and suggest H. naledi is younger than has been previously proposed.
authors.affiliation: Human Evolutionary Studies Program, Simon Fraser University, 8888 University Drive, Burnaby, BC V5A 1S6, Canada; Department of Archaeology, Simon Fraser University, 8888 University Drive, Burnaby, BC V5A 1S6, Canada; Evolutionary Studies Institute and Centre for Excellence in PaleoSciences, University of the Witwatersrand, Private Bag 3, Wits 2050, South Africa. Electronic address: mana.dembo@sfu.ca.
authors.forename: Mana
authors.initials: M
authors.lastname: Dembo
authors.affiliation: Evolutionary Studies Institute and Centre for Excellence in PaleoSciences, University of the Witwatersrand, Private Bag 3, Wits 2050, South Africa; Department of Geology and Paleontology, Croatian Natural History Museum, Demetrova 1, 10000 Zagreb, Croatia.
authors.forename: Davorka
authors.initials: D
authors.lastname: Radovčić
authors.affiliation: Evolutionary Studies Institute and Centre for Excellence in PaleoSciences, University of the Witwatersrand, Private Bag 3, Wits 2050, South Africa; Department of Applied Forensic Sciences, Mercyhurst University, Erie, PA 16546, USA; Department of Anthropology/Archaeology, Mercyhurst University, Erie, PA 16546, USA.
authors.forename: Heather M
authors.initials: HM
authors.lastname: Garvin
authors.affiliation: Evolutionary Studies Institute and Centre for Excellence in PaleoSciences, University of the Witwatersrand, Private Bag 3, Wits 2050, South Africa; Center for the Study of Human Origins, Department of Anthropology, New York University, New York, NY 10003, USA; New York Consortium in Evolutionary Primatology, New York, NY 10024, USA.
authors.forename: Myra F
authors.initials: MF
authors.lastname: Laird
authors.affiliation: Evolutionary Studies Institute and Centre for Excellence in PaleoSciences, University of the Witwatersrand, Private Bag 3, Wits 2050, South Africa; Department of Archaeology, University of Cape Town, Rondebosch 7701, South Africa; Department of Anthropology, University at Buffalo SUNY, Buffalo, NY 14261, USA.
authors.forename: Lauren
authors.initials: L
authors.lastname: Schroeder
authors.affiliation: Evolutionary Studies Institute and Centre for Excellence in PaleoSciences, University of the Witwatersrand, Private Bag 3, Wits 2050, South Africa; Department of Anthropology, The University of Iowa, Iowa City, IA 52242, USA; Department of Sociology and Anthropology, Metropolitan State University of Denver, CO 80217-3362, USA.
authors.forename: Jill E
authors.initials: JE
authors.lastname: Scott
authors.affiliation: Evolutionary Studies Institute and Centre for Excellence in PaleoSciences, University of the Witwatersrand, Private Bag 3, Wits 2050, South Africa; Department of Geography and Anthropology, Louisiana State University, Baton Rouge, LA 70803, USA.
authors.forename: Juliet
authors.initials: J
authors.lastname: Brophy
authors.affiliation: Department of Archaeology, University of Cape Town, Rondebosch 7701, South Africa; Human Evolution Research Institute, University of Cape Town, Rondebosch 7701, South Africa.
authors.forename: Rebecca R
authors.initials: RR
authors.lastname: Ackermann
authors.affiliation: Evolutionary Studies Institute and Centre for Excellence in PaleoSciences, University of the Witwatersrand, Private Bag 3, Wits 2050, South Africa; Department of Anthropology, University of Colorado, Denver, CO 80217, USA.
authors.forename: Chares M
authors.initials: CM
authors.lastname: Musiba
authors.affiliation: Evolutionary Studies Institute and Centre for Excellence in PaleoSciences, University of the Witwatersrand, Private Bag 3, Wits 2050, South Africa; Department of Anthropology, Texas A&M University, College Station, TX 77843, USA.
authors.forename: Darryl J
authors.initials: DJ
authors.lastname: de Ruiter
authors.affiliation: Human Evolutionary Studies Program, Simon Fraser University, 8888 University Drive, Burnaby, BC V5A 1S6, Canada; Department of Biological Sciences, Simon Fraser University, 8888 University Drive, Burnaby, BC V5A 1S6, Canada. Electronic address: amooers@sfu.ca.
authors.forename: Arne Ø
authors.initials: AØ
authors.lastname: Mooers
authors.affiliation: Human Evolutionary Studies Program, Simon Fraser University, 8888 University Drive, Burnaby, BC V5A 1S6, Canada; Department of Archaeology, Simon Fraser University, 8888 University Drive, Burnaby, BC V5A 1S6, Canada; Evolutionary Studies Institute and Centre for Excellence in PaleoSciences, University of the Witwatersrand, Private Bag 3, Wits 2050, South Africa; Department of Archaeology, University of Aberdeen, St Mary's Building, Elphinstone Road, Aberdeen, AB24 3UF, UK. Electronic address: mcollard@sfu.ca.
authors.forename: Mark
authors.initials: M
authors.lastname: Collard
mesh_terms: D000818:Animals; D001499:Bayes Theorem; D005075:Biological Evolution; D005580:Fossils / Q000033:anatomy & histology*; D015186:Hominidae / Q000033:anatomy & histology* / Q000145:classification*; D010802:Phylogeny
keywords: Bayesian phylogenetic analysis; Dinaledi hominins; Genus Homo; Morphological clock