On the environment of Aramis a comment on White in Domínguez-Rodrigo

Department of Geology, University of Utah, 115 South 1460 East, Room 383 Sutton Building, Salt Lake City, Utah 84112, U.S.A. (Cerling and Brown) ([e-mail])/ Department of Geology, University of South Florida, Tampa, Florida 33620, U.S.A. (Wynn). This paper was submitted 9 I 14 and accepted 9 I 14. Tim D. White incorrectly represents our work and the use of stable isotopes to understand Aramis paleoenvironments (Domı'nguez-Rodrigo 2014, comment by Tim D. White). He states that Cerling and colleagues (2010, 2011) "parsed Ardipithecus habitat as grassland rather than a mosaic spanning grassy woodlands to wooded grassland" (Domı´nguez-Rodrigo 2014, comment by White, 75). However, Cerling et al. (2010) wrote, "we find the environmental context of Ardipithecus ramidus at Aramis to be represented by what is commonly referred to as tree- or bush-savanna, with 25% or less woody canopy cover. The habitats involved probably ranged from riparian forest to grassland," and further, "if woodland or closed forest habitat was indeed present, . . . [it] might be found in a riparian corridor bordered by mixed and more open environments, including woody grasslands with ! 25% canopy cover." And yet further, "Evidence from Aramis and elsewhere clearly shows that open savanna grassland was not the environmental context of Ardipithecus." None of these statements parses the Ardipithecus habitat "as grassland."

Current Anthropology Volume 55, Number 4, August 2014 469 Discussion On the Environment of Aramis A Comment on White in Domı´nguez-Rodrigo Thure E. Cerling, Francis H. Brown, and Jonathan G. Wynn Department of Geology, University of Utah, 115 South 1460 East, Room 383 Sutton Building, Salt Lake City, Utah 84112, U.S.A. (Cerling and Brown) ([e-mail])/ Department of Geology, University of South Florida, Tampa, Florida 33620, U.S.A. (Wynn). This paper was submitted 9 I 14 and accepted 9 I 14. Tim D. White incorrectly represents our work and the use of stable isotopes to understand Aramis paleoenvironments (Do-mı ´nguez-Rodrigo 2014, comment by Tim D. White). He states that Cerling and colleagues (2010, 2011) "parsed Ar-dipithecus habitat as grassland rather than a mosaic spanning grassy woodlands to wooded grassland" (Domı´nguez-Rodrigo 2014, comment by White, 75). However, Cerling et al. (2010) wrote, "we find the environmental context of Ardipithecus ramidus at Aramis to be represented by what is commonly referred to as tree- or bush-savanna, with 25% or less woody canopy cover. The habitats involved probably ranged from riparian forest to grassland," and further, "if woodland or closed forest habitat was indeed present, . . . [it] might be found in a riparian corridor bordered by mixed and more open environments, including woody grasslands with ! 25% canopy cover." And yet further, "Evidence from Aramis and elsewhere clearly shows that open savanna grassland was not the environmental context of Ardipithecus." None of these statements parses the Ardipithecus habitat "as grassland." White claims that our "assertion that Aramis paleosol car-bonates indicate only 5%-25% woody cover is invalid because their regression was anchored by non-African forest end-points, biasing their woody-cover estimates significantly to-ward the open side. An alternative application of the same method and comparative data using only their ‘East African' data set produces an Aramis range of 9%-78% cover" (Do-mı ´nguez-Rodrigo 2014, comment by White, 75 n. 6). We are puzzled that White would compare a total range of values, including a 1 4 sigma outlier, with that of a 1-sigma dis-tribution about a mean value. Figure 1 shows the cumulative probability distribution of woody cover from Aramis (WoldeGabriel et al. 2009). These distributions are based on Cerling et al. (2011) using (1) data on all tropical and sub-tropical soils (N p 76), (2) data excluding tropical forests 2014 by The Wenner-Gren Foundation for Anthropological Research. All rights reserved. 0011-3204/2014/5504-0005$10.00. DOI: 10.1086/ 677210 outside of Africa (N p 67), (3) data from Africa only (N p 36), and (4) data from East Africa only (N p 28). Es-timates of woody cover for Aramis yield averages with 1- sigma distributions of 17 9%, 17 9%, 22 10%, and 2510%, respectively. Thus, all methods indicate the dom-inant biome was "wooded grassland" using the White (1983) classification for African vegetation. For comparison, median percent woody cover at Kanapoi and Kanjera calculated using method 1 are ca. 50% and ! 10%, respectively, indicating wood/ bush/shrubland and grassland, respectively (fig. 1). White (Domı´nguez-Rodrigo 2014, comment by White, 75 n. 6) states, "isotope values among the Aramis colobine spec-imens analyzed show the presence of closed canopy forest patches," but only 2 of 20 analyses indicate such conditions (i.e., δ13C ! 14‰). Kuseracolobus, Pliopapio, and Ardipi-thecus have average δ13C values of 12.6 1.6 (N p 20), 10.9 0.7 (N p 14), and 10.3 0.9 (N p 7), re-spectively. All values for Pliopapio and Ardipithecus fall far outside the range suggestive of closed canopy; furthermore, White et al. (2009) suggest that all Ardipithecus individuals sampled for isotopes at Aramis had C4-based resources as part of their diet (9%-28%). Thus, although closed canopy con-ditions may have been present at Aramis, isotopic arguments cannot be used to say that Ardipithecus used them. White and colleagues (WoldeGabriel et al. 2009) say "the Aramis and adjacent drainage basins expose . . . 300 m of sediments largely deposited in rivers and lakes, and on flood-plains, between 5˜.5 and 3.8 Ma. Within this succession, the Ar. ramidus-bearing rock unit comprises silt and clay beds deposited on a floodplain," an interpretation also preferred independently by Gani and Gani (2011), who also found strong evidence of fluvial sedimentation and suggested the presence of riparian environments. This agrees with Cerling et al. (2010), who suggested "a riparian corridor bordered by mixed and more open environments, including woody grass-lands with ! 25% canopy cover." However, White et al. (2010) say that "expected sedimentological, taxonomic, and tapho-nomic evidence for such settings is absent at the hominid-bearing fossil localities at Aramis." Astonishingly, White and colleagues (Ambrose et al. 2011) state that "geological and paleontological evidence for fluviatile deposition and riparian habitats is absent at Aramis," flatly contradicting their earlier description quoted above. We stand by our original inter-pretation of the isotopic evidence for Aramis biomes-limited closed canopy likely associated with riparian habitats, with extensive wooded grasslands and some true grasslands. References Cited Ambrose, Stanley H., Giday WoldeGabriel, Tim D. White, and Gen Suwa. 2011. The role of paleosol carbon isotopes in reconstructing the Aramis Ardipithecus ramidus habitat: woodland or grassland? PaleoAnthropology 2011: A1. http://www.paleoanthro.org/static/pdfs/psoc_2011_fullabstracts.pdf. Cerling, Thure E., Naomi E. Levin, Jay Quade, Jonathan G. Wynn, David L. This content downloaded from 155.97.11.182 on Wed, 6 Aug 2014 12:26:28 PM All use subject to JSTOR Terms and Conditions 470 Current Anthropology Volume 55, Number 4, August 2014 Figure 1. Cumulative probabilities of woody cover for Aramis, based on 85 paleosol analyses (data from WoldeGabriel et al. 2009). Only one of 85 samples has woody cover 1 0.6, using any method of calculation. For comparison woody cover is shown for Kanapoi (Wynn 2000) and Kanjera (Plummer et al. 2009). A color version of this figure is available online. Fox, John D. Kingston, Richard G. Klein, and Francis H. Brown. 2010. Comment on the paleoenvironment of Ardipithecus ramidus. Science 328(5982):1105-d; author reply 1105-e, doi:10.1126/science.1185274. Cerling, Thure E., Jonathan G. Wynn, Samuel A. Andanje, Michael I. Bird, David Kimutai Korir, Naomi E. Levin, William Mace et al. 2011. Woody cover and hominin environments in the past 6 million years. Nature 476: 51-56. Domı´nguez-Rodrigo, M. 2014. Is the "savanna hypothesis" a dead concept for explaining the emergence of the earliest hominins? Current Anthropology 55(1):59-81 [comment by Tim D. White]. Gani, M. Royhan, and Nahid D. Gani. 2011. River-margin habitat of Ardi-pithecus ramidus at Aramis, Ethiopia 4.4 million years ago. Nature Com-munications 2:602, doi:10.1038/ncomms1610. Plummer, ThomasW., PeterW. Ditchfield, Laura C. Bishop, John D. Kingston, Joseph V. Ferraro, David R. Braun, Fritz Hertel, and Richard Potts. 2009. Oldest evidence of toolmaking hominins in a grassland-dominated ecosys-tem. PLoS One 4(9):e7199, doi:10.1371/journal.pone.0007199. White, F. 1983. The vegetation of Africa. Natural Resources Research, vol. 20. Paris: United Nations. White, Tim D., Stanley H. Ambrose, Gen Suwa, and Giday WoldeGabriel. 2010. Response to comment on the paleoenvironment of Ardipithicus ram-idus. Science 328:1105-e, doi:10.1126/science.1185466. White, Tim D., Stanley H. Ambrose, Gen Suwa, Denise F. Su, David DeGusta, Raymond L. Bernor, Jean-Renaud Boisserie et al. 2009. Macrovertebrate paleontology and the Pliocene habitat of Ardipithecus ramidus. Science 326: 87-93. WoldeGabriel, Giday, Stanley H. Ambrose, Doris Barboni, Raymone Bonne-fille, Laurent Bremond, Brian Currie, David DeGusta et al. 2009. The geo-logical, isotopic, botanical, invertebrate, and lower vertebrate surroundings of Ardipithecus ramidus. Science 326:65e1-65e5. Wynn, Jonathan G. 2000. Paleosols, stable carbon isotopes, and paleoenvi-ronmental interpretation of Kanapoi, Northern Kenya. Journal of Human Evolution 39:411-432. This content downloaded from 155.97.11.182 on Wed, 6 Aug 2014 12:26:28 PM All use subject to JSTOR Terms and Conditions