GEOCHRONOLOGY OF SOUTHERN AFRICAN HOMININ-BEARING LOCALITIES

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1 AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 143: (2010) Letter to the Editor: Geochronology and Palaeoenvironments of Southern African Hominin-Bearing Localities A Reply to Wrangham et al., Shallow-Water Habitats as Sources of Fallback Foods for Hominins GEOCHRONOLOGY OF SOUTHERN AFRICAN HOMININ-BEARING LOCALITIES Wrangham et al. (2009; p 234, Table 2) list the estimated ages and taxonomic status of hominins recovered from the southern African palaeocaves. They do so mostly by placing question marks beside apparent ages. In some cases, both the dates and taxonomic affinity of hominins provided are incorrect or out of date. We are concerned here mostly about the common misreporting and sometimes misrepresentation of dating methodologies, age estimates, and their implications, many of which we have ourselves conducted and published. A recent example is Morris (2010), who reports the age of the StW 573 fossil from Sterkfontein as at least 2.7 Ma citing Clarke (1998), a paper published before a plethora of recent geochronological work (Partridge et al., 1999, 2003; Herries, 2003; Walker et al., 2006; Herries et al., 2009; Pickering et al., 2010) had been undertaken at the site. This misrepresentation leads to further confusion over the likely age of the deposits and mistrust and misunderstanding of wellestablished dating methods (e.g., Gilbert and Grine, 2010). Only recently, through a combination of faunal, palaeomagnetic, electron spin resonance (ESR), and uranium-lead dating have more reliable age estimates for these deposits begun to emerge. The fact that two dating methods do not correlate in some cases is most often due not to the reliability of the geochronological methods but rather to a lack of understanding of context. It is quite clear that only a strategy combining these various methods holds promise for reliable dating of the localities independent of faunal correlation with eastern Africa. An up-to-date list of hominin-bearing sites and their age estimates is presented in Table 1. A comparison of age estimates for Sterkfontein Member 4 using a variety of geochronological methods is also given in Table 2 and illustrates the robust nature of the methods used and the current chronology of the southern African sites. Wrangham et al. (2009) stated that all members of the Makapansgat Limeworks date to between 2.5 and 2.0 Ma and have yielded fossils representing the taxa Australopithecus? Homo and Paranthropus. In their citations they include Kuykendall et al. (2005), despite the fact that this article is concerned only with the completely separate Buffalo Cave fossil locality at Makapansgat, which is not part of the Limeworks system (Latham et al., 1999, 2003). The Buffalo Cave deposits are dated to between 2.0 and 0.8 Ma with nonprimate fossils dating to between 1.07 and 0.78 Ma (Herries et al., 2006a; Hopley et al., 2007a,b). The only mention of the Makapansgat Limeworks is Member 3, which is stated to be Pliocene in age. Sponheimer and Lee-Thorp (1999), who are also cited, state that the Limeworks Australopithecus africanus is dated to 3.0 Ma, citing a number of earlier works only one of which is cited by Wrangham et al. (2009). Nowhere is the original dating study of McFadden et al. (1979) cited which suggested an age of around 3.0 Ma. Wrangham et al. (2009) further cite the PhD thesis of one of us (Herries, 2003). This research is based on a faunal and palaeomagnetic age comparison of Members 1 5, the Central Debris Pile (CDP) as defined by Partridge (2000) and the Original Ancient Entrance deposits (OAE) as per Latham et al. (1999, 2003). In this analysis, it was found that the Australopithecus-bearing deposits of Member 3 recorded a normal magnetic polarity and were estimated to date to between 3.03 and 2.58 Ma, not 2.5 and 2.0 Ma as stated by Wrangham et al. (2009). Depositional rates and fauna further constrain the age to between 2.85 and 2.58 Ma. Member 4 (Partridge, 2000; Member 4a of Partridge, 1979) contained the Au. africanus fossils MLD37/38 and MLD36 and is estimated to be around 2.58 Ma (Warr and Latham, 2007). Despite Wrangham et al. (2009) stating that hominins come from all Members at the Limeworks, they have only been recovered from Members 3 and 4. Moreover, considering the fact that the entire suite of nonhominin-fossil bearing deposits at the Makapansgat Limeworks span over 1 Ma of deposition (3.6 \2.6 Ma; Herries, 2003), it is unlikely that all the Members were deposited under the same environmental regime. While some authors have suggested the presence of multiple species at the Makapansgat Limeworks (e.g., Aguirre, 1970) all of the fossils are generally and more recently agreed to belong to Australopithecus (Wood and Richmond, 2000), the one taxon Wrangham et al. (2009) seem doubtful about. The question of the possible paranthropine affinities of some fossils at Makapansgat is currently unresolved (Crawford et al., 2004). While most researchers consider the fossils to represent only one Grant sponsor: Australian Research Council; Grant number: DP *Correspondence to: Andy I.R. Herries, School of Medical Sciences, Wallace Wurth, University of New South Wales, 2052 Kensington, NSW, Australia. a.herries@unsw.edu.au Received 24 February 2010; accepted 28 June 2010 DOI /ajpa Published online 24 September 2010 in Wiley Online Library (wileyonlinelibrary.com). VC 2010 WILEY-LISS, INC.

2 A REPLY TO WRANGHAM ET AL., TABLE 1. Age estimates of hominin-bearing sites from Southern Africa Site Member Taxon Age References Makapansgat 3 Australopithecus Ma Herries, 2003; Hopley et al., 2007b Makpansgat 4 Australopithecus Ma Herries, 2003; Herries et al., 2010 Sterkfontein 4 (Sts 5 deposits) Australopithecus Ma ( Ma) Herries, 2003; Partridge et al., 2005 Sterkfontein StW 573 deposit (Silberberg) Australopithecus Ma Walker et al., 2006; Pickering et al., 2010 ( Ma) Herries and Shaw, 2010 Sterkfontein Jakovec Australopithecus 4 2 Ma? Partridge et al., 2003 Gladysvale internal Australopithecus Ma Berger et al., 1993; Curnoe, 1999 Kromdraai B 1 Paranthropus? 2.0 Ma Thackeray et al., 2002 Malapa D-E Australopithecus Berger et al., 2010; Dirks et al., 2010 Gondolin GD1/2 Paranthropus 1.8 Ma Herries et al., 2006; Adams et al., 2007 Drimolen Paranthropus/Homo Ma? Keyser et al., 2000; Moggi-Cecchi et al., 2010 Kromdraai B 3 Paranthropus/Homo? Ma Thackeray et al., 2002; Herries et al., 2009 Swartkrans 1 3 Paranthropus/Homo Ma? Balter et al., 2008; Herries et al., 2009 Sterkfontein StW53 infill (5A) Homo Ma Curnoe, 1999; Herries et al., 2009; Herries and Shaw, 2010 Coopers D n/a Paranthropus 1.6 \1.4 Ma De Ruiter et al., 2009 Sterkfontein 5B Paranthropus Ma Curnoe, 1999; Herries et al., 2009 Sterkfontein 5C Homo Ma Curnoe, 1999; Herries et al., 2009; Herries and Shaw, 2010 Gladysvale external Homo Ka Lacruz et al., 2002 TABLE 2. Current age estimates for Member 4 at Sterkfontein based on two chronometric (U-Pb, ESR) and two relative methods (palaeomagnetism, Biostratigraphy) Method Age estimate Data reference ESR Ma Schwarcz et al., 1994 ESR Ma Curnoe, 1999; Herries et al., 2009 Palaeomag Ma Herries, 2003; Herries et al., U-Pb to Ma Pickering and Kramers, Biostrat \2.36 Ma Delson, 1988; Herries et al., Combined Ma species, Australopithecus africanus, Clarke (2008) believes these paranthropine affinities represent a second species of Australopithecus similar to fossil StW 573 from Sterkfontein. Homo is only known from Makapansgat at the Cave of Hearths (Curnoe, 2009), which is not associated with the Limeworks Locality and is younger than 780 ka (Latham and Herries, 2004; Herries and Latham, 2009). We find it odd that Sterkfontein Member 4, the Jakovec Cavern, and the Silberberg Grotto deposits are not mentioned by Wrangham et al. (2009) despite all yielding Australopithecus and Member 4 being one of the most abundant hominin fossil-bearing sites in the world. The Member 4 deposits have been dated to between 2.6 and 2.0 Ma using a variety of methods (Table 2), with Au. africanus fossil Sts 5 representing the youngest at Ma (Herries, 2003; Walker et al., 2006; Herries et al., 2009; Herries and Shaw, 2010; Pickering and Kramers, 2010). The Silberberg Grotto has yielded an apparent second species of Australopithecus, StW 573 (Clarke, 2008), and this likely dates to around Ma based on palaeomagnetism and uranium-lead dating (Walker et al., 2006; Herries and Shaw, 2010; Pickering and Kramers, 2010; Pickering et al., 2010), but is certainly not greater than 2.6 Ma as suggested by Morris (2010). Morris (2010) states that 2.7 Ma is an important age because it suggests StW 573 is either an early form of Au. africanus, or it is the first evidence we have found of Au. afarensis outside of east Africa. The former inference is impossible given the recent younger dating of the StW 573 fossil and its similar age to the youngest Au. africanus fossil Sts 5, while the latter seems highly unlikely given StW 573 s young age. What this does suggest is that two different species of Australopithecus were present at Sterkfontein around Ma. Despite cosmogenic nuclide age estimates of 4 Ma for the Jacovec cavern Australopithecus fossils (Partridge et al., 2003), their age remains unresolved due to questions over the accuracy of the Silberberg grotto cosmogenic ages due to the potential mixing of quartz of different ages in the deposits. Sterkfontein Member 5 is dated by Wrangham et al. (2009) to 1.8 Ma? (see Kuman and Clarke, 2000). Yet Member 5 consists of a number of temporally discrete deposits as defined by Partridge (1979; 2000): Member 5A ( StW53 infill ) contains Homo fossil StW 53 (Curnoe and Tobias, 2006), Member 5B ( Oldowan infill ) contains Paranthropus and Oldowan artifacts and Member 5C ( Acheulian infill ) contains Homo and Acheulian artifacts. On the basis of fauna and artifacts, Kuman and Clarke (2000) suggested M5B to be around Ma, with M5c suggested to date to between 1.7 and 1.4 Ma. M5A is suggested to date to Member 4 times, with StW 53 argued to represent Australopithecus. Again this is very different from the 1.8 Ma? stated by Wrangham et al. (2009). However, a recent combined ESR and palaeomagnetic analysis of Sterkfontein (Herries et al., 2009; Herries and Shaw, in press) suggests that M5A (Homo) is more likely to be around Ma, M5B (Paranthropus and Oldowan) around Ma and M5C (Homo and Acheulian) around Ma. The post- 1.8 Ma age of Member 5 is also suggested by a 1.8Mauranium-lead dating of a flowstone capping Member 4 and deposited before the deposition of Member 5 (Pickering and Kramers, 2010). Wrangham et al. (2009: p 634; Table 2) state that Kromdraii [sic] Member B dates to 2.0 Ma and contains Paranthropus quoting Thackeray et al. (2002),

3 642 A.I.R. HERRIES ET AL. who present a palaeomagnetic analysis of Kromdraai locality B. Again, this is an oversimplification of the likely temporal spread at this locality and a misrepresentation of apparent hominin diversity (i.e., remains attributed to Homo have also been recovered: Braga and Thackeray, 2003). Kromdraai is split into two sites, A and B. The hominin-bearing Kromdraai B contains Members 1 3, with Member 3 containing the majority, if not all, of the hominin fossils, although Thackeray suggests that the type specimen of Paranthropus robustus (TM1517) probably derived from Member 1 based on sediment type attached to the fossil (Thackeray et al., 2002). The adjacent site of Kromdraai A contains numerous faunal remains. Member 1 of Kromdraai B contains the reversal at the beginning of the Olduvai sub-chron and so is around 1.95 Ma and slightly older. Member 2 contains the reversal at the end of the Olduvai event at around 1.78 Ma. The majority of the in situ hominins derive from Member 3, likely dating to between 1.78 and 1.65 Ma (Herries et al., 2009). Wrangham et al. (2009) suggest that the Gondolin palaeocave is dated to 1.5 Ma and cites Watson (1993) and Herries et al. (2006b). Watson (1993) stated that the site likely dated to between 2.0 and 1.5 Ma based on its fauna. Since then, significant revisions to the preliminary faunal list of Watson (1993) were made by Adams and Conroy (2005) and Adams (2006). Their analysis re-diagnosed fauna indicative of edaphic grasslands and wetland palaeohabitats, thereby eliminating these potential habitats during faunal deposition. Moreover, Herries et al. (2006b) and Adams et al. (2007) conducted combined faunal and palaeomagnetic studies on two separate deposits (GD2 and GD1) that contain the majority of the in situ recovered fauna from Gondolin GD2. These deposits both record a normal magnetic polarity followed by a reversed polarity, with the fossils in the older normal polarity zone in GD2 and in the younger reversed polarity zone in GD1. Based on this sequence, the site is suggested by Herries et al. (2006b) and Adams et al. (2007) to date to either side of the reversal at the end of the Olduvai sub-chron around 1.78 Ma. The provenience of the Paranthropus fossils is not certain, but the site is small, and a similar palaeomagnetic sequence is noted in both fossil-bearing areas of the site. As such, it is suggested that the hominin fossils also date to around 1.8 Ma. Gladysvale consists of a number of fossil deposits of varying ages. Wrangham et al. (2009) suggest that Gladysvale has yielded Paranthropus? dated to 2.0 Ma. Yet the Lacruz et al. (2002) study which they cite assesses the fauna and age of the Gladysvale External Deposits (GVED). Only Homo fossils have been recovered from the GVED, which has been dated to between 780 and 578 ka based on palaeomagnetism and ESR (Lacruz et al., 2002; Herries, 2003). Moreover, Lacruz et al. (2002), citing Berger et al. (1993), indicate that Australopithecus (not Paranthropus) was recovered from ex-situ blocks from the site, and these fossils are thought to derive from deposits within the interior of the cave. Pickering et al. (2007) have dated some of the interior deposits to between 600 and 14 ka while Hall et al. (2006) state that further Acheulian-bearing deposits date to [780 ka based on ESR and palaeomagnetism (uncited data from Herries, 2003). ESR data (Curnoe, 1999) suggests that other interior deposits date to perhaps as old as around 2.4 Ma and these are likely the source of the australopithecine teeth. Coopers Locality B contains fossils with uncertain provenience and ex situ fossils attributed to Australopithecus and Homo (Steininger et al., 2008). However, the original fossil attributed to Australopithecus that was recovered from Coopers B in 1938 has gone missing, and as such, its presence at Coopers B cannot be confirmed. Subsequent finds in museum collections have only been attributed to Paranthropus (Steininger et al., 2008), but their provenience is again uncertain (de Ruiter et al., 2009). Coopers Locality D has also yielded Paranthropus and has recently been dated to between and \1.4Mausing uranium-lead dating (de Ruiter et al., 2009). Wrangham et al. (2009) make no mention of this second set of welldated fossils. Recently another major hominin site has been discovered and described by Berger et al. (2010) and Dirks et al. (2010). The site of Malapa has yielded the remains of two partial skeletons attributed to a new hominin species, Australopithecus sediba. Speleothem underlying the fossil deposits has been dated using U-Pb to Ma and contains the Huckleberry Ridge geomagnetic event at 2.05 Ma (Dirks et al., 2010). The hominin-bearing deposits themselves (Facies D and E) record a normal magnetic polarity and are correlated to the beginning of the Olduvai sub-chron between 1.95 and 1.78 Ma. A last appearance date of 1.5 Ma for Megantereon whitei rules out the deposit being correlated to a younger normal polarity period. The fossil is likely closer to 1.95 Ma than 1.78 Ma and suggest that a number of different hominin species occurred on the South African landscape between 2.2 and 1.8 Ma. Environment of Southern African hominin localities Central to the argument of Wrangham et al. (2009) is that all early hominin populations had access to shallowwater habitats for collecting USOs. This is despite large variation in geographic and temporal differences. The meteorological and palaeoclimatic evidence presented to support the presence of aquatic environments at African Plio- Pleistocene hominin localities is equivocal. Lake levels have repeatedly risen and fallen during the Plio-Pleistocene of eastern Africa (Trauth et al., 2005), often in response to changes in the Earth s orbit (Kingston, 2007). Lacustrine (e.g., Trauth et al., 2005) and wetland deposits (e.g. Ashley et al., 2009) are common within the sedimentary sequences of eastern Africa, as are drier phases as indicated by palaeosols and fossil grasslands (e.g., Bamford et al., 2008; Plummer et al., 2009). Lake-margin wetlands would have been common during wet phases and minimal during dry phases (Dühnforth et al., 2006); some small groundwater-fed wetlands may have persisted through dry phases, as indicated by Ashley et al. (2009). Given the observations of large-scale variability in African rainfall in the past (e.g., Trauth et al., 2005; Hopley et al., 2007a), the modern rainfall and temperature data summarized in Table 3 of Wrangham et al. (2009) has little bearing on the Plio-Pleistocene climate of Africa, or their discussion of wetland habitats. The summary of site-based palaeoenvironmental reconstructions presented in Table 2 of Wrangham et al. (2009) is perhaps a more reliable indicator of the potential presence of wetlands at southern African sites. However, their analysis of the southern African sites relies on a 52-yearold thesis (Brain, 1958) and omits many recent papers on the palaeoenvironments and climates associated with the southern African sites they discuss (e.g., Hopley et al., 2006, 2007a; Lee-Thorp et al., 2007; Pickering et al., 2007). Their summary of the selected literature shows

4 A REPLY TO WRANGHAM ET AL., that the eight southern African palaeocaves studied fall into one of the following categories: Grassland adjacent to (small) glade or Grassland with woodland along streams. These reconstructions are based principally on the ecomorphological work of Reed (1997). Most of her reconstructions are of a highly diverse environment of riparian woodland and edaphic grasslands with a minor wetland component. The recent isotopic and palaeoenvironmental work suggests that the earlier South African sites ([2.0 Ma; Sterkfontein Member 4 and the Makapansgat Limeworks Member 3 and 4) are in much more wooded environments and that only a small component of grassland is present (Sponheimer and Lee-Thorp, 2003; Hopley et al., 2006; Schubert et al., 2006). The wetland component from these sites is reconstructed from the small percentage of the assemblage with a masticatory morphology similar to grazers that inhabit modern seasonal wetlands (Peters and Vogel, 2005). Hopley and Maslin (2010) have put forward an alternative interpretation of the Reed (1997) data by suggesting that the southern African faunal assemblages were accumulated under more than one climatic state. Accumulation during periodic wet and dry phases (precessional cycles) may be responsible for the wide range of ecomorphologies observed in these assemblages. This implies that the small percentage of (possible) wetland species was accumulated during wet phases, rather than being a permanent feature of the landscape. The palaeoenvironmental evidence is not consistent with the idea that the Makapansgat or Bloubank valleys supported extensive wetlands (Peters and Vogel, 2005), or a significant source of C4 plant food such as USOs (Sponheimer et al., 2005). All of the southern African sites are palaeocave deposits and so must in some way be associated with water in the form of small streams or underground rivers. This is very different from the suggestion by Wrangham et al. (2009) that the presence of palaeocave deposits implies association with widespread flooded glades or surface water. On most karst terrains, significant surface water will be limited, as it is locked underground unless saturation of the subsurface zone has occurred due to significant rainfall. We also disagree with the idea that all the caves were associated with similar landscapes and environments regardless of their age and speleogenetic origin. The various caves developed in landscapes of greatly varying topography and hydrology, as indicated by the stratigraphy and development of the various cavities (see Wilkinson, 1983; Latham et al., 2003; Latham and Herries, 2004; Herries, 2006a,b; Adams et al., 2007). For example, Gondolin occurred in a more mountainous area where significant surface water accumulations would have been unlikely, and this is reflected by a lack of wetland species (Adams, 2006). Equally, the upper reaches of the modern Makapansgat Valley represent an area formed by the collapse of a much larger cave system that once linked the Cave of Hearths and the Limeworks caves (Latham and Herries, 2004). The oldest sedimentary deposits in the Cave of Hearths are less than 780 ka and as such the area would not have reached something equating its modern form until the middle Pleistocene (Herries and Latham, 2009). Recent cosmogenic nuclide analysis by Dirks et al. (2010) on landscapes around Malapa and Gladysvale suggest that m Ma 21 of sediment has been eroded from the hilltops in the region, and rivers had incised by mMa 21. This means that rivers may have incised by 150 m and hilltops by 12 m since the hominin fossils were deposited at the oldest site of the Makapansgat Limeworks. Similarly, Wrangham et al. s (2009) use of the modern landscape as an indicator of past wetlands is unsupported by the data. As a whole, the southern African subcontinent is characterized by an old, flat and tectonically stable landsurface devoid of wetlands (McCarthy and Hancox, 2000). The principal exceptions are the Okavango region, which is situated within a seismically active graben system, an extension of the east African rift system, and some localized neotectonic activity associated with Precambrian faults such as Nylsvley near Makapansgat. The Nylsvley wetland usually dries out completely during early winter; however, it can remain inundated for several years during prolonged wet periods (Scholes and Walker, 1993). The minor seasonal wetlands of the southern African interior associated with rivers, vleis and dambos are all shallow, with little open water, and dry up in winter, including the minor wetlands of the Bloubank stream in the Sterkfontein Valley. While well-developed USOs are common in extensive wetlands like the Okavango delta, they are not abundant at riverine environments in South Africa today (Sponheimer et al., 2005). Similarly, there is little evidence for extensive wetland deposits in the Plio-Pleistocene of the southern African highveld (Peters and Vogel, 2005; Sponheimer et al., 2005; Adams and Conroy, 2005; Adams, 2006; Hopley et al., 2007a), indicating that early hominin species were likely not dependent on USO consumption in this region of Africa. Given present knowledge of the paleogeography of this region, it seems unlikely that wetlands were widespread during the Plio-Pleistocene of southern Africa. The extensive Okavango/Makgadikgadi wetlands of Botswana, for example, formed only during the late Quaternary (Burrough et al., 2009), and are a special case formed following late Pliocene uplift of the Kalahari and impoundment of the Okavango, Kwando, and Zambezi drainage. The wetlands of the Okavango delta, and the baboon populations they support, are best viewed as modern analogues of the Plio-Pleistocene lake-margins of eastern Africa, where there is evidence that hominins were exploiting aquatic resources in a well watered habitat as early as 1.95 Ma (Braun et al., 2010). This is not the case for the very different environments in southern Africa. Because some underwater USOs belong to plants that use the C4 photosynthetic pathway, Wrangham et al. (2009) quote the stable isotope literature to support their hypothesis that early hominins consumed USOs. A recent study by van der Merwe et al. (2008) produced the first carbon isotope measurements from eastern African hominins (Homo habilis and Paranthropus boisei), with the preliminary finding that H. habilis had a mixed diet (20 50% C4), whereas P. boisei had a C4 dominated diet (80% C4). Meat is an unlikely source of such a high proportion of C4 in the P. boisei diet, due to the protein poisoning effects of such a high protein diet and a dental morphology unsuitable for excessive meat consumption. van der Merwe et al. (2008) concluded that the C4 dietary signature of P. boisei is more likely to reflect the exploitation of water margin C4 sedges such as papyrus. However, when compared with P. boisei, the southern African hominins, Au. africanus, P. robustus, andhomo sp. all have a much smaller proportion of C4 in their diet (15 55%; van der Merwe et al., 2008). The dietary source of this C4 signal is uncertain: various combinations of meat, termites, and USOs have been suggested (e.g., Peters and Vogel, 2005; Sponheimer et al., 2005). Additional lines of evidence in support of significant meat consumption by the southern African hominins

5 644 A.I.R. HERRIES ET AL. include butchery at Swartkrans (Pickering et al., 2008) and possible vertebral pathology relating to meat consumption (brucellosis) in Au. africanus from Sterkfontein (D Anastasio et al., 2009). Direct evidence for termite foraging in southern Africa comes from bone tool morphology and wear associated with P. robustus (e.g., Backwell and d Errico, 2001). There is as yet neither a direct evidence for USO consumption in southern African hominins nor a need to invoke significant wetland USO consumption on the basis of the carbon isotope evidence (Peters and Vogel, 2005). Our interpretation of the palaeoenvironmental and stable isotope evidence is that there is a strong regional difference in wetland resource use: intermittent wetland habitats and significant USO consumption by some eastern African hominins (e.g., P. bosei) and dry savannah/ woodland habitats in southern Africa with minimal USO consumption. Wetland plant resources and aquatic resources may have been extensively exploited by some early hominins, but it is premature to suggest that aquatic habitats were a necessary condition for the adaptation to savannah habitats or facilitated the evolution of habitual bipedalism. It is clear that further research into early hominin diets and habitats is required before wetland environments can be given anything approaching a central role in the narrative of human evolution. ACKNOWLEDGMENTS The authors thank two anonymous reviewers who helpfully commented on the manuscript and Robyn Pickering who read an earlier draft. They thank all the site directors (Kaye Reed, Kevin Kuykendall, Lee Berger, Ron Clarke, Francis Thackeray) with whom they have worked over the years and also to the late Tim Partridge who worked extensively to better understand the geology and geochronology of the southern African hominin-bearing sites. ANDY I.R. HERRIES UNSW Archaeomagnetism Laboratory Integrative Palaeoecological and Anthropological Studies School of Medical Sciences University of New South Wales Kensington 2052, NSW, Australia PHILIP J. HOPLEY Department of Earth and Planetary Sciences Birkbeck College University of London Malet Street, Bloomsbury, London, WC1E 7HX, UK JUSTIN W. ADAMS Department of Biomedical Sciences Grand Valley State University Allendale, MI School of Anatomical Sciences University of the Witwatersrand 7 York Road, Parktown, Johannesburg 2193 RSA, South Africa DARREN CURNOE School of Biological, Earth and Environmental Sciences University of New South Wales Kensington 2052, NSW, Australia MARK A. MASLIN Department of Geography University College London Gower Street, London, WC1E 6BT, UK LITERATURE CITED Adams JW Taphonomy and paleoecology of the Gondolin Plio-Pleistocene cave site, South Africa. Ph.D. thesis, Department of Anthropology, Washington University in St. Louis. Adams JW, Conroy GC Plio-Pleistocene faunal remains from the Gondolin GD 2 in situ assemblage, North West Province, South Africa. In: Lieberman D, Smith RJ, Kelley J, editors. Interpreting the past: essays on human, primate and mammal evolution in honor of David Pilbeam. Boston: Brill Academic. p Adams JW, Herries AIR, Conroy GC, Kuykendall KL Taphonomy of a South African cave: geological and hydrological influences on the GD 1 fossil assemblage at Gondolin, a Plio-Pleistocene paleocave system in the Northwest Province. South Africa. Quat Sci Revs 26: Aguirre E Identification de Paranthropus en Makapansgat. Cronica de XI Congr Natl de Arquilogie Merido 1969: Ashley GM, Tactikos JC, Owen RB Hominin use of springs and wetlands: paleoclimate and archaeological records from Olduvai Gorge ( Ma). Palaeogeogr Palaeoclimatol Palaeoecol 272:1 16. Backwell LR, d Errico F Evidence of termite foraging by Swartkrans early hominids. Proc Natl Acad Sci USA 98: Balter V, Blichert-Toft J, Braga J, Telouk P, Thackeray F, Albarède F U-Pb dating of fossil enamel from the Swartkrans Pleistocene hominid site. South Africa. Earth Planet Sci Lett 267: Bamford MK, Stanistreet IG, Stollhofen H, Albert RM Late Pliocene grassland from Olduvai Gorge, Tanzania. Palaeogeogr Palaeoclimatol Palaeoecol 257: Berger LR, De Ruiter DJ, Churchill SE, Schmid P, Carlson KJ, Dirks PHGM, Kibii JM Australopithecus sediba: a new species of Homo-like Australopith from South Africa. Science 328: Berger LR, Keyser AW, Tobias PV Brief communication: Gladysvale: first early hominid site discovered in South Africa since Am J Phys Anthropol 92: Braga J, Thackeray JF Early Homo at Kromdraai B: probabilistic and morphological analysis of the lower dentition. Comp Rend Palevol 2: Brain CK The transvaal ape-man-bearing cave deposits. Pretoria: Transv Mus Mem. p 11. Braun DR, Harris JWK, Levin NE, McCoy JT, Herries AIR, Bamford M, Bishop L, Richmond BR, Kibunjia M Early hominin diet included diverse terrestrial and aquatic animals 1.95 Ma ago in East Turkana, Kenya. PNAS 107: Burrough SL, Thomas DSG, Singarayer JS Late Quaternary hydrological dynamics in the Middle Kalahari: forcing and feedbacks. Earth Sci Rev 96: Clarke RJ First ever discovery of a well-preserved skull and associated skeleton of an Australopithecus. S Afr J Sci 94: Clarke RJ Latest information on Sterkfontein s Australopithecus skeleton and a new look at Australopithecus. S Afr J Sci 104: Crawford T, McKee JK, Kuykendall KL, Latham AG, Conroy GC Recent paleoanthropological excavations of in situ deposits at Makapansgat. South Africa a first report. Coll Antropol 28: Curnoe D A contribution to the question of early Homo. Unpublished Ph.D. thesis, Australian National University. Curnoe D The Bed 3 mandible. In: McNabb J, Sinclair A, editors. The cave of Hearths: Makapan middle pleistocene research project. Southampton Monographs in Archaeology. Oxford: Archaeopress. 1: Curnoe D, Tobias PV Description, new reconstruction, comparative anatomy, and classification of the Sterkfontein StW 53 cranium, with discussions about the taxonomy of other southern African early Homo remains. J Hum Evol 50: D Anastasio R, Zipfel B, Moggi-Cecchi J, Stanyon R, Capasso L Possible brucellosis in an early hominin skeleton from Sterkfontein, South Africa. PLoS ONE 4:e6439.

6 A REPLY TO WRANGHAM ET AL., de Ruiter DJ, Pickering R, Steininger CM, Kramers JD, Hancox PJ, Churchill SE, Berger LR, Backwell L New Australopithecus robustus fossils and associated U-Pb dates from Cooper s Cave (Gauteng. South Africa). J Hum Evol 56: Dirks PHDM, Kibii JN, Kuhn BF, Steininger C, Churchill SE, Kramers JD, Pickering R, Farber DL, Mériaux S-A, Herries AIR, King GCP, Berger LR Geological setting and age of Australopithecus sediba from southern Africa. Science 328: Dühnforth M, Bergner A, Trauth M Early Holocene water budget of the Nakuru-Elmenteita basin, Central Kenya Rift. J Paleolimnol 36: Gilbert CC, Grine FE Morphometric variation in the Papionin Muzzle and the biochronology of the South African Plio-Pleistocene karst cave deposits. Am J Phys Anthropol 141: Hall G, Pickering R, Lacruz R, Hancox J, Berger LR, Schmid P An Acheulean handaxe from Gladysvale Cave site, Gauteng, South Africa. S Afri J Sci 102: Herries AIR Magnetostratigraphic seriation of South African hominin paleocaves. Ph.D. thesis, University of Liverpool. Herries AIR, Adams JW, Kuykendall KL, Shaw J. 2006a. Speleology and magnetobiostratigraphic chronology of the GD 2 locality of the Gondolin hominin-bearing paleocave deposits. North West Province, South Africa. J Hum Evol 51: Herries AIR, Curnoe D, Adams JW A multi-disciplinary seriation of early Homo and Paranthropus bearing palaeocaves in southern Africa. Quat Int 202: Herries AIR, Latham AG Archaeomagnetic studies at the Cave of Hearths. In: McNabb J, Sinclair AGM, editors. The Cave of Hearths: Makapan middle pleistocene research project. Southampton Monographs in Archaeology. Oxford: Archaeopress. 1: Herries AIR, Reed K, Kuykendall KL, Latham AG. 2006b. Speleology and Magnetobiostratigraphic chronology of the Buffalo Cave fossil bearing palaeodeposits. Makapansgat, South Africa. Quat Res 66: Herries AIR, Shaw J Palaeomagnetic analysis of the Sterkfontein palaeocave deposits; age implications for the hominin fossils and stone tool industries. J Human Evolution. Accepted June Hopley PJ, Latham AG, Marshall JD Palaeoenvironments and palaeodiets of mid-pliocene micromammals from Makapansgat Limeworks, South Africa: a stable isotope and dental microwear approach. Palaeogeog Palaeoclimat Palaeoecol 233: Hopley PJ, Marshall JD, Weedon GP, Latham AG, Herries AIR, Kuykendall KL. 2007b. Orbital forcing and the spread of C4 grasses in the late Neogene: stable isotope evidence from South African speleothems. J Hum Evol 53: Hopley PJ, Maslin MA Climate-averaging of terrestrial faunas: an example from the Plio-Pleistocene of South Africa. Paleobiol 36: Hopley PJ, Weedon GP, Marshall JD, Herries AIR, Latham AG, Kuykendall KL. 2007a. High- and low-latitude orbital forcing of early hominin habitats in South Africa. Earth Planet Sci Lett 256: Keyser AW, Menter CG, Moggi-Cecchi J, Pickering TR, Berger LR Drimolen: a new hominid-bearing site in Gauteng, South Africa. S Afr J Sci 96: Kingston JD Shifting adaptive landscapes: progress and challenges in reconstructing early hominid environments. Yearb Phys Anthropol 134: Kuman K, Clarke RJ Stratigraphy, artefact industries and hominid associations for Sterkfontein, M5. J Hum Evol 38: Kuykendall KL, Toich CA, McKee JK Preliminary analysis of the fauna from Buffalo Cave, northern Transvaal, South Africa. Palaeontol Afr 32: Lacruz RS, Brink JS, Hancox J, Skinner AS, Herries A, Schmidt P, Berger LR Palaeontology, geological context and palaeoenvironmental implications of a Middle Pleistocene faunal assemblage from the Gladysvale Cave, South Africa. Palaeontol Afr 38: Latham AG, Herries AIR The formation and sedimentary infilling of the Cave of Hearths and Historic Cave Complex. Geoarchaeology 19: Latham AG, Herries AIR, Kuykendall K The formation and sedimentary infilling of the Limeworks Cave, Makapansgat, South Africa. Palaeontol Afr 39: Latham AG, Herries A, Quinney P, Sinclair A, Kuykendall K The Makapansgat Australopithecine site from a speleological perspective. In: Pollard AM, editor. Geoarchaeology: exploration, environments, resources. London: Royal Geological Society, Special Publications 165: Lee-Thorp JA, Sponheimer M, Luyt J Tracking changing environments using stable carbon isotopes in fossil tooth enamel: an example from the South African hominin sites. J Hum Evol 53: McCarthy TS, Hancox PJ Wetlands. In: Partridge TC, Maud RR, editors. The Cenozoic of southern Africa. Oxford: Oxford University Press. p McFadden PL, Brock A, Partridge TC Paleomagnetism and the age of the Makapansgat hominid site. Earth Planet Sci Lett 44: Moggi-Cecchi J, Menter C, Boccone S, Keyser A Early hominin dental remains from the Plio-Pleistocene site of Drimolen, South Africa. J Hum Evol 58: Morris AG New hominin fossils from Malapa: the unveiling of Australopithecus sediba. S Afr J Sci 106:3 4. Partridge TC Re-appraisal of lithostratigraphy of Makapansgat Limeworks hominid site. Nature 279: Partridge TC Hominid-bearing cave and tufa deposits. In: Partridge TC, Maud RR, editors. The Cenozoic of southern Africa. Oxford: Oxford University Press. p Partridge TC Dating of the Sterkfontein hominids: progress and possibilities. Trans R Soc S Afr 60: Partridge TC, Granger DE, Caffee MW, Clarke RJ Lower Pliocene hominid remains from Sterkfontein. Science 300: Partridge TC, Shaw J, Heslop D, Clarke RJ The new hominid skeleton from Sterkfontein, South Africa: age and preliminary assessment. J Quat Sci 14: Peters CR, Vogel JC Africa s wild C4 plant foods and possible early hominid diets. J Hum Evol 48: Pickering TR, Egeland CP, Domínguez-Rodrigo M, Brain CK, Schnell AG Testing the shift in the balance of power hypothesis at Swartkrans, South Africa: hominid cave use and subsistence behavior in the Early Pleistocene. J Anthropol Archaeol 27: Pickering R, Hancox PJ, Lee-Thorp JA, Grün R, Mortimer GE, McCulloch M, Berger LR Stratigraphy, U-Th chronology, and paleoenvironments at Gladysvale Cave: insights into the climatic control of South African hominin-bearing cave deposits. J Hum Evol 53: Pickering R, Kramers J Re-appraisal of the stratigraphy and determination of new U-Pb dates for the Sterkfontein hominin site, South Africa. J Hum Evol 59: Pickering R, Kramers JD, Partridge T, Kodolanyi J, Pettke T U-Pb dating of calcite-aragonite layers in speleothems from hominin sites in South Africa by MC-ICP-MS. Quat Geochron doi: /j.quageo Plummer TW, Ditchfield PW, Bishop LC, Kingston JD, Ferraro JV, Braun DR, Hertel F, Potts R Oldest evidence of tool-making hominins in a grassland-dominated ecosystem. PLoS ONE 4:e7199. Reed KE Early hominid evolution and ecological change through the African Plio-Pleistocene. J Hum Evol 32: Scholes RJ, Walker BH An African savanna: synthesis of the Nylsvley study. Cambridge: Cambridge University Press. Schubert BW, Ungar PS, Sponheimer M, Reed KE Microwear evidence for Plio-Pleistocene bovid diets from Makapansgat Limeworks Cave, South Africa. Palaeogeog Palaeoclimat Palaeoecol 241: Sponheimer M, Lee-Thorp JA Isotopic evidence for the diet of an early hominid, Australopithecus africanus. Science 283:

7 646 A.I.R. HERRIES ET AL. Sponheimer M, Lee-Thorp JA Using carbon isotope data of fossil bovid communities for palaeoenvironmental reconstruction. S Afr J Sci 99: Sponheimer M, Lee-Thorp J, de Ruiter D, Codron D, Codron J, Baugh AT, Thackeray F Hominins, sedges, and termites: new carbon isotope data from the Sterkfontein valley and Kruger National Park. J Hum Evol 48: Steininger C, Berger LR, Kuhn BF A partial skull of Paranthropusrobustus from Cooper s Cave, South Africa. S Afr J Sci 104: Thackeray JF, Kirschvink JL, Raub TD Palaeomagnetic analysis of calcified deposits from the Plio-Pleistocene hominid site of Kromdraai, South Africa. S Afr J Sci 98: Trauth MH, Maslin MA, Deino A, Strecker MR Late Cenozoic moisture history of East Africa. Science 309: van der Merwe NJ, Masao FT, Bamford M Isotopic evidence for contrasting diets of early hominins Homo habilis and Australopithecus boisei of Tanzania. S Afr J Sci 104: Walker J, Cliff RA, Latham AG U-Pb isotopic age of the StW 573 hominid from Sterkfontein, South Africa. Science 314: Warr GL, Latham AG Normal magnetic polarity provenance for MLD 37/38, an in situ hominin from the Makapansgat Limeworks, South Africa. Am J Phys Anthropol 132:244. Watson V Glimpses from Gondolin: a faunal analysis of a fossil site near Broederstroom. Transvaal, South Africa. Palaeont Afr 30: Wilkinson MJ Geomorphic perspectives on the Sterkfontein australopithecine breccias. J Arch Sci 10: Wrangham R, Cheney D, Seyfarth R, Sarmiento E Shallow-water habitats as sources of fallback foods for hominins. Am J Phys Anthropol 140: Wood BA, Richmond BG Human evolution: taxonomy and paleobiology. J Anat 196:19 60.