title: Late Miocene to Pliocene carbon isotope record of differential diet change among East African herbivores.
abstract: Stable isotope and molecular data suggest that C(4) grasses first appeared globally in the Oligocene. In East Africa, stable isotope data from pedogenic carbonate and fossil tooth enamel suggest a first appearance between 15-10 Ma and subsequent expansion during the Plio-Pleistocene. The fossil enamel record has the potential to provide detailed information about the rates of dietary adaptation to this new resource among different herbivore lineages. We present carbon isotope data from 452 fossil teeth that record differential rates of diet change from C(3) to mixed C(3)/C(4) or C(4) diets among East African herbivore families at seven different time periods during the Late Miocene to the Pliocene (9.9-3.2 Ma). Significant amounts of C(4) grasses were present in equid diets beginning at 9.9 Ma and in rhinocerotid diets by 9.6 Ma, although there is no isotopic evidence for expansive C(4) grasslands in this part of the Late Miocene. Bovids and hippopotamids followed suit with individuals that had C(4)-dominated (>65%) diets by 7.4 Ma. Suids adopted C(4)-dominated diets between 6.5 and 4.2 Ma. Gomphotheriids and elephantids had mostly C(3)-dominated diets through 9.3 Ma, but became dedicated C(4) grazers by 6.5 Ma. Deinotheriids and giraffids maintained a predominantly C(3) diet throughout the record. The sequence of differential diet change among herbivore lineages provides ecological insight into a key period of hominid evolution and valuable information for future studies that focus on morphological changes associated with diet change.
authors.affiliation: Department of Geology and Geophysics, University of Utah, Salt Lake City, UT 84112, USA. kevin.uno@utah.edu
authors.forename: Kevin T
authors.initials: KT
authors.lastname: Uno
authors.forename: Thure E
authors.initials: TE
authors.lastname: Cerling
authors.forename: John M
authors.initials: JM
authors.lastname: Harris
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Kunimatsu
authors.forename: Meave G
authors.initials: MG
authors.lastname: Leakey
authors.forename: Masato
authors.initials: M
authors.lastname: Nakatsukasa
authors.forename: Hideo
authors.initials: H
authors.lastname: Nakaya
mesh_terms: D000351:Africa, Eastern; D000818:Animals; D005075:Biological Evolution; D002247:Carbon Isotopes / Q000032:analysis / Q000378:metabolism; D003743:Dental Enamel; D005247:Feeding Behavior; D005580:Fossils
chemical_list: D002247:Carbon Isotopes