期刊
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
卷 113, 期 23, 页码 6355-6363出版社
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1521267113
关键词
leaf wax; carbon isotope; mammalian evolution; molecular distribution; hominin
资金
- Center for Climate and Life at the Lamont-Doherty Earth Observatory (LDEO) of Columbia University
- US National Science Foundation [OCE-1359194]
- Division Of Ocean Sciences
- Directorate For Geosciences [1359194] Funding Source: National Science Foundation
The evolution of C-4 grassland ecosystems in eastern Africa has been intensely studied because of the potential influence of vegetation on mammalian evolution, including that of our own lineage, hominins. Although a handful of sparse vegetation records exists from middle and early Miocene terrestrial fossil sites, there is no comprehensive record of vegetation through the Neogene. Here we present a vegetation record spanning the Neogene and Quaternary Periods that documents the appearance and subsequent expansion of C-4 grasslands in eastern Africa. Carbon isotope ratios from terrestrial plant wax biomarkers deposited in marine sediments indicate constant C-3 vegetation from similar to 24 Ma to 10 Ma, when C-4 grasses first appeared. From this time forward, C-4 vegetation increases monotonically to present, with a coherent signal between marine core sites located in the Somali Basin and the Red Sea. The response of mammalian herbivores to the appearance of C-4 grasses at 10 Ma is immediate, as evidenced from existing records of mammalian diets from isotopic analyses of tooth enamel. The expansion of C-4 vegetation in eastern Africa is broadly mirrored by increasing proportions of C-4-based foods in hominin diets, beginning at 3.8 Ma in Australopithecus and, slightly later, Kenyanthropus. This continues into the late Pleistocene in Paranthropus, whereas Homo maintains a flexible diet. The biomarker vegetation record suggests the increase in open, C-4 grassland ecosystems over the last 10 Ma may have operated as a selection pressure for traits and behaviors in Homo such as bipedalism, flexible diets, and complex social structure.
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