Paleoenvironment of Australopithecus anamensis at Allia Bay,East Turkana,Kenya: evidence from mammalian herbivore enamel stable isotopes |
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| Affiliation: | 1. Department of Anthropology, University of California at San Diego, La Jolla, CA 92093-0532, USA;2. Department of Anthropology, University of Wisconsin, Madison, WI 53706, USA;1. Department of Anthropology, University of Minnesota, 395 Hubert H. Humphrey Center, 301 19th Avenue South, Minneapolis, MN 55455, USA;2. Department of Earth Sciences, University of Minnesota, 310 Pillsbury Drive SE, Minneapolis, MN 55455, USA;3. Department of Anthropology, Peabody Museum of Archaeology and Ethnology, Harvard University, 11 Divinity Avenue, Cambridge, MA 02138, USA;4. School of Social Science, The University of Queensland, Brisbane, QLD 4072, Australia;5. Department of Geology, Baylor University, One Bear Place #97354, Waco, TX 76798, USA;6. Department of Geology and Geophysics, Texas A&M University, MS3115, College Station, TX 77843, USA;1. Sackler Educational Laboratory for Comparative Genomics and Human Origins, American Museum of Natural History, New York, NY, USA;2. Department of Anthropology, The Graduate Center, City University of New York, New York, NY, USA;3. Department of Anthropology, Queens College, City University of New York, Flushing, New York, USA;4. Department of Anthropology, Lehman College, City University of New York, Bronx, New York, USA;5. New York Consortium in Evolutionary Primatology, New York, NY, USA;1. Department of Anthropology, Washington University in St. Louis, St. Louis, MO 63130, USA;2. Department of Anthropology, University of Florida, Gainesville, FL 32611-7305, USA;3. Department of Anthropology and Geography, Colorado State University, Fort Collins, CO 80523-1787, USA;4. Center for Research in Archaeogeophysics and Geoarchaeology (CRAG), Colorado State University, Fort Collins, CO 80523-1787, USA;5. Department of Anthropology, University of Illinois at Champaign-Urbana, Champaign, IL 61820, USA;1. Center for Applied Isotope Studies, University of Georgia, GA, USA;2. Anthropology Department, University of Alaska, Fairbanks, AK, USA;3. University of Alaska, Museum of the North, Fairbanks, AK, USA |
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| Abstract: | Carbon (13C:12C) and oxygen (18O:16O) stable isotope ratio analysis was performed on well-preserved tooth enamel carbonate from fossil fauna recovered from a single excavation at the early hominid site of Allia Bay, East Turkana, Kenya. These data show greater enrichment in both 12C and in 16O than expected, based on the oxygen isotope composition of the middle Pliocene ocean, and on today’s ecology. The pattern of these data argues against a diagenetic explanation for the enrichment. The carbon stable isotope data of known browsers suggest a more extensive canopy cover during the middle Pliocene than today’s environments. The presence of browsing pig genera, hippo genera, deinotheres, and giraffes with δ13C values more negative than today’s all argue for woodland habitats. The presence of several grazing genera point to the presence of grasslands as well. The oxygen stable isotope ratios indicate that the site was better-watered than today, although the source, seasonal pattern, and actual amount of water cannot be determined from these data. The overall mosaic of environments suggested by these data, in combination with reports of exotic trees recovered in nearby deposits, indicate that woodlands were present in the region 3.9 my, unlike today. Such a setting matches expectations for the selective advantages of nut-eating, bipedal hominids over other hominoids. |
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