Meyer M.R.,Chaffey College |
Williams S.A.,New York University |
Smith M.P.,American Museum of Natural History |
Sawyer G.J.,American Museum of Natural History
Journal of Human Evolution | Year: 2015
The Australopithecus afarensis partial skeleton A.L. 288-1, popularly known as "Lucy" is associated with nine vertebrae. The vertebrae were given provisional level assignments to locations within the vertebral column by their discoverers and later workers. The continuity of the thoracic series differs in these assessments, which has implications for functional interpretations and comparative studies with other fossil hominins. Johanson and colleagues described one vertebral element (A.L. 288-1am) as uniquely worn amongst the A.L. 288-1 fossil assemblage, a condition unobservable on casts of the fossils. Here, we reassess the species attribution and serial position of this vertebral fragment and other vertebrae in the A.L. 288-1 series. When compared to the other vertebrae, A.L. 288-1am falls well below the expected size within a given spinal column. Furthermore, we demonstrate this vertebra exhibits non-metric characters absent in hominoids but common in large-bodied papionins. Quantitative analyses situate this vertebra within the genus Theropithecus, which today is solely represented by the gelada baboon but was the most abundant cercopithecoid in the KH-1s deposit at Hadar where Lucy was discovered. Our additional analyses confirm that the remainder of the A.L. 288-1 vertebral material belongs to A.afarensis, and we provide new level assignments for some of the other vertebrae, resulting in a continuous articular series of thoracic vertebrae, from T6 to T11. This work does not refute previous work on Lucy or its importance for human evolution, but rather highlights the importance of studying original fossils, as well as the efficacy of the scientific method. © 2015 Elsevier Ltd.
Khatiwada B.K.,Oklahoma State University |
Hetayothin B.,MissouriUniversity of Science and Technology |
Hetayothin B.,Chaffey College |
Blum F.D.,Oklahoma State University
Macromolecular Symposia | Year: 2013
The behavior of an amorphous polymer, poly(methyl methacrylate) (PMMA), adsorbed on silica was studied using temperature-modulated differential scanning calorimetry (TMDSC). A two-component model, based on loosely-bound polymer with a glass transition temperature (Tg) (similar to that of the bulk polymer) and a tightly-bound polymer (with a Tg higher than that of the loosely-bound polymer) was used to interpret the thermograms. Increased sensitivity allowed the two transitions in the thermograms to be quantified much more accurately than in previous work. Linear regression analysis of the ratio of the area under two transitions with composition yielded the amount of tightly bound polymer, m″B = 1.21 +/- 0.21 mg PMMA/m 2silica. Two methods of analyzing the thermograms, fitting with a Gaussian-Lorentzian (GL) cross distribution function and perpendicular drop (PD) method, yielded similar results for the amount of tightly-bound polymer on the surfaces with the GL method having a statistically better fit to the model. The ratio of heat capacity increments of loosely bound and tightly bound polymer, ΔCpA/ΔCpB, around the glass transition, indicated the relative mobility of the two components. It was found that the ΔCpA was aboutthree times as large as that of ΔC pB suggesting that the tightly bound polymer had a much smaller change in mobility through glass transition region. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Meyer M.R.,Chaffey College |
Haeusler M.,University of Zurich
Journal of Human Evolution | Year: 2015
The discovery at Nariokotome of the Homo erectus skeleton KNM-WT 15000, with a narrow spinal canal, seemed to show that this relatively large-brained hominin retained the primitive spinal cord size of African apes and that brain size expansion preceded postcranial neurological evolution. Here we compare the size and shape of the KNM-WT 15000 spinal canal with modern and fossil taxa including H. erectus from Dmanisi, Homo antecessor, the European middle Pleistocene hominins from Sima de los Huesos, and Pan troglodytes. In terms of shape and absolute and relative size of the spinal canal, we find all of the Dmanisi and most of the vertebrae of KNM-WT 15000 are within the human range of variation except for the C7, T2, and T3 of KNM-WT 15000, which are constricted, suggesting spinal stenosis. While additional fossils might definitively indicate whether H. erectus had evolved a human-like enlarged spinal canal, the evidence from the Dmanisi spinal canal and the unaffected levels of KNM-WT 15000 show that unlike Australopithecus, H. erectus had a spinal canal size and shape equivalent to that of modern humans. Subadult status is unlikely to affect our results, as spinal canal growth is complete in both individuals. We contest the notion that vertebrae yield information about respiratory control or language evolution, but suggest that, like H. antecessor and European middle Pleistocene hominins from Sima de los Huesos, early Homo possessed a postcranial neurological endowment roughly commensurate to modern humans, with implications for neurological, structural, and vascular improvements over Pan and Australopithecus. © 2015 Elsevier Ltd.
Berger L.R.,University of Witwatersrand |
Hawks J.,University of Witwatersrand |
Hawks J.,University of Wisconsin - Madison |
de Ruiter D.J.,University of Witwatersrand |
And 88 more authors.
eLife | Year: 2015
Homo naledi is a previously-unknown species of extinct hominin discovered within the Dinaledi Chamber of the Rising Star cave system, Cradle of Humankind, South Africa. This species is characterized by body mass and stature similar to small-bodied human populations but a small endocranial volume similar to australopiths. Cranial morphology of H. naledi is unique, but most similar to early Homo species including Homo erectus, Homo habilis or Homo rudolfensis. While primitive, the dentition is generally small and simple in occlusal morphology. H. naledi has humanlike manipulatory adaptations of the hand and wrist. It also exhibits a humanlike foot and lower limb. These humanlike aspects are contrasted in the postcrania with a more primitive or australopith-like trunk, shoulder, pelvis and proximal femur. Representing at least 15 individuals with most skeletal elements repeated multiple times, this is the largest assemblage of a single species of hominins yet discovered in Africa. © Berger et al.
News Article | October 16, 2014
Mars has been seeing a lot of action lately, between NASA's string of rovers and new projects from Elon Musk and Mars One. But what would it take to set up a permanent settlement there? Could humans survive in such a harsh and alien setting? In this week's Big Future, Adrianne Jeffries takes a look at the nuts and bolts of a martian settlement, from food shipments to radiation management. There are a lot of problems, but we've got good ideas about how to solve them. The most encouraging sign is the discovery of water ice on Mars. (There's even some evidence it was once liquid water.) If the colony set up next to a martian glacier, it could potentially convert the ice into drinkable water and breathable air. That would go a long way towards providing for the basic needs of early colonists. We don't have any idea how to produce food in Martian soil, so even the most ambitious settlements will rely on years of food shipments from Earth. Still, any meaningful colony would have to create a self-sufficient food supply eventually, either through industrial or agricultural breakthroughs. And then there's the radiation... Background radiation is thousands of times higher on Mars than it is on Earth, so even if we succeed in all the other areas, settlers would still probably face shorter and less healthy lives on Mars. Human beings simply didn't evolve for the Martian environment. But despite the many problems, Mars is still basically as good as it gets. It's close, relatively similar in climate, and there's enough sunlight to run solar power grids. If we can't make it work there, we won't be able to make it work anywhere. If you're still curious, you can read Elon Musk's plans for a Martian colony, or check out the early materials from Mars One. And check back next week, when The Big Future takes a look at rewiring the human brain.