title: Laetoli footprints reveal bipedal gait biomechanics different from those of modern humans and chimpanzees.
abstract: Bipedalism is a key adaptation that shaped human evolution, yet the timing and nature of its evolution remain unclear. Here we use new experimentally based approaches to investigate the locomotor mechanics preserved by the famous Pliocene hominin footprints from Laetoli, Tanzania. We conducted footprint formation experiments with habitually barefoot humans and with chimpanzees to quantitatively compare their footprints to those preserved at Laetoli. Our results show that the Laetoli footprints are morphologically distinct from those of both chimpanzees and habitually barefoot modern humans. By analysing biomechanical data that were collected during the human experiments we, for the first time, directly link differences between the Laetoli and modern human footprints to specific biomechanical variables. We find that the Laetoli hominin probably used a more flexed limb posture at foot strike than modern humans when walking bipedally. The Laetoli footprints provide a clear snapshot of an early hominin bipedal gait that probably involved a limb posture that was slightly but significantly different from our own, and these data support the hypothesis that important evolutionary changes to hominin bipedalism occurred within the past 3.66 Myr.
authors.affiliation: Department of Human Evolution, Max Planck Institute for Evolutionary Anthropology, Deutscher Platz 6, 04103 Leipzig, Germany Center for the Advanced Study of Human Paleobiology, Department of Anthropology, The George Washington University, 800 22nd Street NW, Suite 6000, Washington, DC 20052, USA kevin.g.hatala@gmail.com.
authors.forename: Kevin G
authors.identifier: 0000-0001-9131-5304
authors.initials: KG
authors.lastname: Hatala
authors.affiliation: Department of Anatomical Sciences, Health Sciences Center, Stony Brook University, Stony Brook, NY 11794, USA.
authors.forename: Brigitte
authors.initials: B
authors.lastname: Demes
authors.affiliation: Department of Human Evolution, Max Planck Institute for Evolutionary Anthropology, Deutscher Platz 6, 04103 Leipzig, Germany Division of Anthropology, American Museum of Natural History, New York, NY 10024, USA.
authors.forename: Brian G
authors.initials: BG
authors.lastname: Richmond
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D005528:Foot; D005684:Gait; D015186:Hominidae / Q000502:physiology*; D006801:Humans; D002679:Pan troglodytes; D013636:Tanzania
keywords: Laetoli; biomechanics; locomotion; palaeoanthropology