GSA Connects 2021 in Portland, Oregon

Paper No. 38-12
Presentation Time: 4:45 PM


PEPPE, Daniel1, COTE, Susanne2, DEINO, Alan L.3, FOX, David L.4, KINGSTON, John D.5, KINYANJUI, Rahab N.6, LUKENS, William E.7, MACLATCHY, Laura M.8, NOVELLO, Alice9, STROMBERG, Caroline10, DRIESE, Steven11, GARRETT, Nicole12, HILLIS, Kayla R.13, JACOBS, Bonnie F.14, JENKINS, Kirsten E.15, KITYO, Robert16, LEHMANN, Thomas17, MANTHI, Fredrick K.6, MBUA, Emma N.6, MICHEL, Lauren13, MILLER, Ellen18, MUGUME, Amon19, NENGO, Isaiah20, OGINGA, Kennedy Ogonda21, PHELPS, Samuel R.22, ROSSIE, James B.23, STEVENS, Nacny J.24, UNO, Kevin25 and MCNULTY, Kieran P.26, (1)Department of Geosciences, Baylor University, One Bear Place #97354, Waco, TX 76798-7354, (2)Department of Anthropology and Archaeology, University of Calgary, Calgary, AB 2N 1N4, Canada, (3)Berkeley Geochronology Center, 2455 Ridge Road, Berkeley, CA 94709, (4)Department of Earth Sciences, University of Minnesota, Minneapolis, MN 55455, (5)Department of Anthropology, University of Michigan, 101 West Hall, 1085 S. University Ave, Ann Arbor, MI 48109-1107, (6)Earth Sciences, National Museums of Kenya, P.O Box 40658-00100, Nairobi, 254, Kenya, (7)Department of Geology and Environmental Science, James Madison University, Harrisonburg, VA 22807-1004, (8)Department of Anthropology, University of Michigan, Ann Arbor, MI 48109, (9)Aix-Marseille Université, Jardin du Pharo, 58 Boulevard Charles Livon, Marseille, 13007, France; Department of Biology, University of Washington, Life Sciences Building (LSB), Box 351800, Seattle, WA 98195-1800, (10)Department of Biology, Burke Museum of Natural History and Culture, University of Washington, Box 351800, Seattle, WA 98195, (11)Department of Geosciences, Baylor University, Waco, TX 76798, (12)National Marrow Donor Program, 500 North 5th St., Minneapolis, MN 55401; Department of Geology and Geophysics, University of Minnesota, 310 Pillsbury Drive SE, Minneapolis, MN 55455-0219, (13)Department of Earth Sciences, Tennessee Tech University, Box 5062, Cookeville, TN 38505, (14)Huffington Dept. Earth Sciences, Southern Methodist University, PO Box 750395, Dallas, TX 75275, (15)Department of Social Sciences, Tacoma Community College, 6501 S 19th Street, Tacoma, WA 98466, (16)Department of Biological Sciences, Makerere University, P.O Box 7062, Kampala, 8HP8+99, Uganda, (17)Messel Research and Mammalogy Department, Senckenberg Research Institute and Natural History Museum Frankfurt, Senckenberganlage 25, Frankfurt, 60325, Germany, (18)Department of Anthropology, Wake Forest University, Winston-Salem, NC 27106, (19)Department of Biological Sciences, Makerere University, P.O Box 7062, Kampala, 8HP8+99, Uganda; Department of Museums and Monuments, Uganda National Museum, Ministry of Tourism, Wildlife and Antiquities, Kira Rd, Kampala, 8HPJ+6W, Uganda, (20)Turkana Basin Institute, Stony Brook University, Stony Brook, NY 11794, (21)Terra Guidance, Englewood, CO 80110; Terrestrial Paleoclimatology Research Group, Department of Geosciences, Baylor University, One Bear Place, #97354, Waco, TX 76798, (22)Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA 02138, (23)Department of Anthropology, Stony Brook University, Stony Brook, NY 11794, (24)Department of Biomedical Sciences, Heritage College of Osteopathic Medicine, Ohio University, Athens, OH 45701, (25)Biology and Paleo Environment, Lamont-Doherty Earth Observatory, 61 Route 9W, PO Box 1000, Palisades, NY 10964, (26)Department of Anthropology, University of Minnesota, 395 Hubert H. Humphrey Center, 301 19th Avenue South, Minneapolis, MN 55455

The assembly of Africa’s iconic C4 grassland and savanna ecosystems is central to evolutionary interpretations of many mammals, including hominins. Based largely on pollen, biomarkers, and isotopic data, C4 grasses are thought to have become ecologically dominant in Africa only after 10 Ma. However, paleobotanical records older than 10 Ma are sparse, hindering a full assessment of the timing and nature of C4 biomass expansion. Here, we use a multi-proxy approach, combining analyses of phytoliths and stable carbon isotopes from soil organic matter, plant waxes, and pedogenic carbonates to document vegetation structure from ten early Miocene fossil hominoid sites across eastern Africa (Kenya and Uganda). Although not every source of (proxy) data were available for all sites, there is sufficient overlap at multiple sites to provide a detailed and robust view of early Miocene vegetation. Taken together, our results demonstrate that, between 21 and 17 Ma, C4 grasses were locally abundant in vegetation at all sites, but not for every sample from those sites, such that they contributed to habitat heterogeneity ranging from closed forests to wooded grasslands. This pattern points to heterogeneity in vegetation both within and among sites (locally to regionally) during the early Miocene. It also pushes back the oldest fossil evidence of C4 grass-dominated habitats in Africa – and globally – by over 10 million years, calling for new paleoecological interpretations of mammalian evolution, not least that of our own lineage.