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How old are the Bose (Baise) Basin (Guangxi, southern China) bifaces? The Australasian tektites question revisited
Journal of Human Evolution 80 (2015) 171e174
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Journal of Human Evolution journal homepage: www.elsevier.com/locate/jhevol
News and views
How old are the Bose (Baise) Basin (Guangxi, southern China) bifaces? The Australasian tektites question revisited Wei Wang a, *, Christopher J. Bae b, * a b
Guangxi Museum of Nationalities, Nanning, Guangxi 530022, China Department of Anthropology, University of Hawai'i at Manoa, 2424 Maile Way, 346 Saunders Hall, Honolulu, HI 96822, USA
a r t i c l e i n f o Article history: Received 8 July 2014 Accepted 27 October 2014 Available online 3 December 2014
Introduction The age of the Bose Basin bifaces has long been debated in palaeoanthropology (e.g., Hou et al., 2000; Koeberl and Glass, 2000; Potts et al., 2000). In light of our recent article published in this journal (Wang et al., 2014), Langbroek (2015) raises similar questions about the association of the Australasian tektites and the Bose Basin bifaces that were mentioned earlier by Koeberl and Glass (2000). Langbroek's (2015) argument is based on two points: 1) using examples from mainland Southeast Asia, he suggests there is ample or strong evidence of vertical displacement of the tektites; and 2) he questions our interpretation of the tektite surface morphology to argue against in situ deposition of the tektites. We address each of these points in turn. Vertical displacement of the tektites Langbroek (2015) argues that the depositional sequence of Bose is similar to other areas of the Australasian strewnfield (e.g., Thailand, Laos, Vietnam). Citing works by Fiske et al. (1996, 1999) from Southeast Asia, Langbroek concludes that the sedimentary sequence in Bose is the result of reworking and is nothing more than a lag deposit that contains materials of different ages, including from the Holocene, as is apparently the case for many sites in mainland Southeast Asia. In our opinion, the Bose Basin tektites are geomorphologically, stratigraphically and sedimentologically different from the
* Corresponding authors. E-mail addresses: [email protected] (W. Wang), [email protected] (C.J. Bae). http://dx.doi.org/10.1016/j.jhevol.2014.10.013 0047-2484/© 2014 Elsevier Ltd. All rights reserved.
Southeast Asian examples cited by Langbroek. At least five fluvial terraces developed in the Bose Basin, with the tektites overwhelmingly appearing in the laterite of the upper part of terrace 4 (‘T4’). To date, there are only two exceptions to this: two abraded slightly rounded tektites were found in the gravel bed in T3 in the central part of the basin (Fig. 1, the left and middle tektites in the bottom row) and one heavily abraded tektite was found in the lower reaches of the Youjiang River (Fig. 1, the right tektite in the bottom row) (Wang et al., 2008). Terrace 4 is the most typical river terrace with the largest distribution in the basin. The T4 sequence is extremely stable, consisting of upper laterite (5e10 m in thickness) and an underlying gravel bed (2e10 m in thickness). This sequence is evident throughout the basin in numerous exposed and excavated profiles. Terrace 4 strata can be clearly divided into four units from top to bottom: Unit-1, brown surface loess-like deposit, distributed only in a few well-preserved platforms, unconformity with underlain laterite, 20e40 cm in thickness; Unit-2, red sandy-clay (laterite), containing stone artifacts occasionally, 1e3 m in thickness; Unit-3, reticular mottled red clay, containing typical stone artifacts, tektites are located in the middle of this unit, 4e6 m in thickness; Unit-4, grey gravel bed, well-sorted, 2e10 m in thickness (Fig. 2). Unit-1 is thin, and obviously distinguishes from the underlying Unit-2. A distinct boundary does not exist between Unit-2 and Unit3, which display transitional features. The different characteristics of Unit-2 and Unit-3 are probably due to variation in exposure to weathering, with the latter unit more severely affected. The tektite layer is concentrated in the middle of Unit-3, the reticular mottled red clay. Unit-3 is homogeneous, with no evidence of a paleoerosional surface. There is no evidence from the T4 profiles of marked vertical redeposition or the mixing of materials from different temporal periods and/or cultural units. The Bose Basin stratigraphy is not similar to the Southeast Asian sites cited by Langbroek. It should be noted that Langbroek (2015) has suggested that Figure 3 from the Nanbanshan locality in Damei (Wang et al., 2008) can be used as evidence that much of the deposits in Bose were subjected to vertical reworking with artifacts from T2 and T3 being moved to T4. Unfortunately, Langbroek has misread the stratigraphic profile from the Nanbanshan site. In the Wang et al. (2008: 878) study, it was specifically stated that “[t]he Nanbanshan locality of the Damei
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Figure 1. To date, only three of the more than 275 tektites found in Bose were recovered from T3. The first two rows present typical tektites from T4, while the bottom row presents the three abraded and worn tektites recovered from T3.
site (23 46.6640 N,106 43.7200 E) is located on terrace 4 of the Youjiang River in the southeast Youjiang district of Bose City (Fig.1).” (emphasis added). Nowhere in the Wang et al. (2008) paper is it stated that T2 and T3 are found overlying T4 at the Nanbanshan site. In fact, if that were the case, the deposits would be many tens of meters thick. The stratigraphic profile presented in Figure 3 from Wang et al. (2008) of that paper represents only deposits from T4. Thus, Langbroek's interpretation of the Nanbanshan stratigraphy is unwarranted. Nevertheless, if vertical reworking of the various strata in Bose is the most parsimonious explanation to rationalize the association of
the Australasian tektites and the bifaces, we ask the following questions then: 1) Why do the bifaces only appear in T4? 2) Why is there a paucity of evidence of hominin occupation in T3 and T2? 3) Why are there clear Neolithic occupations only in T1? If Langbroek (2015) is correct that the examples from mainland Southeast Asia are equally applicable to the Chinese case and the Bose materials are extensively reworked vertically, we should expect to find Neolithic artifacts (e.g., pottery, ground stone tools) appearing, minimally in T4 in association with the supposedly younger handaxes and older tektites. However, this does not appear to be the
Figure 2. This photograph is taken at Gaolingpo, a recently excavated (2014) Paleolithic site in eastern Bose Basin. Units 1 to 3 are presented, the underlying Unit-4 is not shown.
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case. For researchers familiar with the Chinese Paleolithic and Neolithic, there are noticeable differences between the types and morphologies of artifacts found in Early Paleolithic and Neolithic sites in Guangxi (e.g., compare the artifacts from Wang et al., 2014; Li et al., in press). After more than four decades of research in Bose, primarily by Chinese scientists but also in collaboration with American researchers (e.g., R. Potts, C.J. Bae), such a mixed deposit of Neolithic and Early Paleolithic artifacts has yet to be identified. Because Neolithic artifacts have failed to systematically appear in other terraces (e.g., T2eT4) in the basin (and vice-versa for the bifaces and tektites), we question Langbroek's argument that the depositional sequence in Bose (and purported reworking of the deposits) is the same as that which appears in mainland Southeast Asia. Further, Langbroek (2015) raises the possibility that availability or non-availability of raw materials may explain the absence of stone tools in the upper terraces. However, as we noted in our original paper (Wang et al., 2014), the hominins occupying the Bose Basin were clearly relying on locally- and readily-available raw materials. Because of possible lower population densities in eastern Asia during the Pleistocene (cf. Lycett and Norton, 2010), it is possible that the Bose Basin was sparsely occupied or even completely abandoned for long periods of time (see Huang et al., 2012; Xu et al., 2012 for variation in site distributions across the basin). This, in our opinion, is a more parsimonious explanation for the paucity of sites in T3 and T2 than arguing that the Bose hominins used T4 for certain activities and T3 and T2 for other activities, as suggested by Langbroek (2015). We are not the only ones to argue that in certain cases at least some of the Australasian tektites were found in situ. For instance, Shoemaker and Uhlherr (1999) identified a series of sites in Australia where the tektites did not likely move very far after landing. Haines et al. (2004) more recently identified at least one site in northeast Thailand where the tektites appear to be found in situ. Indeed, Haines et al. (2004: 26) note that “consistent with a very brief time period between impact and burial is the lack of abrasion on the tektites from unit A, implying very limited residence time in a high energy alluvial environment, or to exposure at the surface” (emphasis added). In fact, Haines et al.’s (2004) reflection does not differ significantly from our own observations of many of the Bose tektites that appear to lack any evidence of extensive abrasion (Wang et al., 2014). Other differences between other areas within the Australasian strewnfield and Bose exist as well. For instance, at the Uhlherr's Good Spot in Australia, more than 260 tektites were collected in an area <80 m in length and ~30 m in width (Shoemaker and Uhlherr, 1999; see also Fiske et al., 1996, 1999 for discussion of high tektite densities in Southeast Asia). Although we have not conducted a systematic investigation of tektite densities in the Bose Basin, it would appear to be far lower than comparably sized regions in mainland Southeast Asia and Australia. To date, only about 275 tektites have been found throughout the entire Bose Basin. In addition, the overall size of individual tektites appears to be significantly different. Indeed, Fiske et al. (1999) note that one Southeast Asian fragmented mass alone may have originally weighed as much as 1000 kg. The Bose Basin tektites are fist-sized and smaller. The lower tektite density and sizes in Bose would in fact not be all that surprising given the fact that Guangxi is considered the northernmost extension of the Australasian tektite distribution. Tektite surface morphology More than 50 years ago, Chapman and Larson (1963) reviewed a wide diversity of hypotheses that have been proposed to explain
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the origin of, and related to this current debate, the morphology of the tektites. The debate regarding the morphology of tektites can be broadly grouped into two camps: 1) predepositional aerodynamic explanations, and 2) postdepositional chemical erosion explanations. Langbroek (2015) cites a number of studies (e.g., Rost, 1969; Lamarche et al., 1984; Barnes, 1990) that not surprisingly fall in the latter camp and is used to support his argument that we misunderstand the true meaning of the morphology of the tektites (in our original paper, we argued for predepositional aerodynamic modification and minimal postdepositional movement). However, it should be noted that there are a number of other studies (e.g., Chapman et al., 1962; Chapman and Larsen, 1963; Johnson, 1965; O'Keefe, 1967) that were not cited by Langbroek, but in fact support the predepositional aerodynamic explanation. For instance, hypervelocity ablation experiments in the laboratory have reproduced the same surface sculptures, geometric shapes, systematic striae distortions, and coiled circumferential flanges as those found on tektites from Australia (Chapman and Larson, 1963). In any case, the moldavites from Central Europe are often cited as the primary evidence of tektite chemical erosion (e.g., Rost, 1969; Langbroek, 2015). However, the Central European moldavites are ~14.5 Ma (millions of years ago) and the Australasian tektites date to no more than 803 ka (thousands of years ago). Even if chemical erosion is a major influence in the morphology of the 14.5 Ma moldavites, it may be possible that not enough time has passed for that process to have had a significant influence on the Australasian tektites. Only experimental studies specific to the Australasian tektites would be able to verify or refute the hypothesis that the morphology of these tektites is a direct result of chemical erosion (see, for example, Barkatt et al., 1984, 1986, 1989; Mazer et al., 1992). In relation to our own analysis and interpretation of the Australasian tektites that are present in Bose, there does not appear to be anything blatantly incorrect with what we said in our original study (contra Langbroek, 2015). If anything, as earlier studies have argued (e.g., Potts et al., 2000) and as we note here and elsewhere (Wang et al., 2014), there appears to be relatively little movement of the tektites postdepositionally (either laterally or vertically) (see also Shoemaker and Uhlherr, 1999; Haines et al., 2004 for similar examples in other regions of the Australasian strewnfield). Needless to say, concluding that the predepositional aerodynamic argument makes sense in explaining the morphology of the Bose tektites should not be equated with arguing for the now disproven hypothesis that all tektites are of lunar origin (for review see Koeberl, 1994). We are simply using the Bose tektite morphology to suggest that the tektites have not been significantly moved from a different terrace, particularly because the Bose tektites are so restricted to one specific terrace, a situation that appears to differ fairly clearly from many other regions of Southeast Asia and Australia. Discussion Although Langbroek (2015) recommends that we try other dating methods to crosscheck the age of the Bose Basin sites and materials, it should be noted that we have already made some attempts. For instance, Deng et al. (2007) conducted a paleomagnetic analysis of the sedimentary sequence from the Damei site. Unfortunately, because of strong chemical weathering that occurs due to the subtropical condition in southern China a chemical remanent magnetization overprint is sufficiently strong to mask the primary natural remanent magnetization. The Deng et al. (2007) study indicated that magnetostratigraphic studies on red soil sequences in subtropical and tropical southern China should be interpreted with great caution. More recently, Guangjun Shen, Darryl Granger, and colleagues have been searching the Bose Basin's fourth terrace
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for areas that are over 10 m thick in order to attempt a cosmogenic 26 Al/10Be burial dating analysis of the quartz sediments (Personal communication from G.J. Shen). As noted above, there are a series of differences between the Bose Basin and mainland Southeast Asia and Australia situations, which would suggest they are not exactly comparable and should be treated differently. In addition, the argument for chemical etching, particularly using the examples of the 14.5 Ma Central European moldavites, to refute minimal postdepositional movement of the Bose tektites is not, in our opinion, very strongly supported. Future experimental studies that focus on the Australasian tektites could potentially shed light on the rate of chemical erosion and what other variables would need to be factored in. Nevertheless, the Bose Basin tektites are clearly concentrated in the reticular mottled red clay of T4, with only two examples of wellrounded and abraded tektites appearing in T3. There is little evidence of vertical movement of the materials (e.g., we do not find Early Paleolithic bifacial implements mixed in the same stratigraphic layers as Neolithic pottery sherds and ground stone tools). If anything, assuming the Early Paleolithic bifaces originated from T4 and the tektites moved vertically from T3 or T2, then in fact, by default this would make the Bose bifaces older than the EarlyMiddle Pleistocene transition. Because of the high concentration of Early Paleolithic stone tools and tektites in a restricted sequence of T4, we are not going to make that argument. However, it is interesting if one reversed the argument and tried to make the case that the stone tools are in original deposition and the tektites moved vertically from an overlying terrace (this is something that could be read from the Koeberl and Glass, 2000 paper). Just some food for thought as the true meaning of the Bose tektites continues to be discussed. The nature of the Movius Line will likely continue to be debated (e.g., Hou et al., 2000; Norton et al., 2006; Lycett and Bae, 2010; Lycett and Norton, 2010) and understanding the age of the eastern Asian bifaces contributes an important part to deciphering the true meaning of the line. We sincerely appreciate scientists raising questions about the depositional history of the Australasian tektites in the Bose Basin and their relationship to the bifaces. However, until proven otherwise “anything found in T4 can be confidently associated with the tektites” (Wang et al., 2014: 116). Acknowledgements Funding for this research is from the 2014 University of Hawai'i at Manoa College of Social Sciences Research Award. The initial draft of this response was written while we were out in the middle of fieldwork in Guangxi, China. We thank Kathryn Burns, based in Hawai'i at the time, who was able to track down some of the more difficult-to-find references for us on short notice. We appreciate the comments from Christian Koeberl and an anonymous reviewer that helped to tighten up the text. We take full responsibility for any errors that may be present. References Barkatt, A., Boulos, M.S., Barkatt, Al., Sousanpour, W., Boroomand, M.A., Macedo, P.B., O'Keefe, J.A., 1984. The chemical durability of tektites-A laboratory
study and correlation with long-term corrosion behavior. Geochim. Cosmochim. Acta 48, 361e371. Barkatt, A., Saad, E.E., Adiga, R., Sousanpour, W., Barkatt, Al., Alterescu, S., 1986. Leaching of microtektite glass compositions in seawater. Adv. Ceram. 20, 68le687. Barkatt, A., Saad, E.E., Adiga, R., Sousanpour, W., Barkatt, Al., Adel-Hadadi, M.A., O'Keefe, J.A., 1989. Leaching of natural and nuclear waste glasses in seawater. Appl. Geochem. 4, 593e603. Barnes, V.E., 1990. Tektite research 1936e1990. Meteoritics 25, 149e159. Chapman, D.R., Larson, H.K., 1963. On the lunar origin of tektites. J. Geophys. Res. 68, 4305e4358. Chapman, D.R., Larson, H.K., Lewis, A.A., 1962. Aerodynamic evidence pertaining to the entry of tektites into the earth's atmosphere. NASA Tech. Rept. R-134. Deng, C.L., Liu, Q., Wang, W., Liu, C.C., 2007. Chemical overprint on the natural remanent magnetization of a subtropical red soil sequence in the Bose Basin, southern China. Geophys. Res. Lett. 34, L22308. Fiske, P.S., Putthapiban, P., Wasson, J.Y., 1996. Excavation and analysis of layered tektites from northeast Thailand: results of 1994 field expedition. Meteor. Planet. Sci. 31, 36e41. Fiske, P.S., Schnetzler, C.C., McHone, J., Chanthavaichith, K.K., Homsombath, I., Phouthakayalat, T., Khenthavong, B., Xuan, P.T., 1999. Layered tektites of Southeast Asia: Field studies in central Laos and Vietnam. Meteor. Planet. Sci. 34, 757e761. Haines, P.W., Howard, K.T., Ali, J.R., Burrett, C.F., Bunopas, S., 2004. Flood deposits penecontemporaneous with 0.8 Ma tektite fall in NE Thailand: impact-induced environmental effects? Earth Planet. Sci. Lett. 225, 19e28. Hou, Y.M., Potts, R., Yuan, B.Y., Guo, Z.T., Deino, A., Wang, W., Clark, J., Xie, G.M., Huang, W.W., 2000. Mid-Pleistocene Acheulean-like stone technology of the Bose Basin, south China. Science 287, 1622e1626. Huang, S.M., Wang, W., Bae, C.J., Xu, G.L., Liu, K.T., 2012. Recent Paleolithic field investigations in Bose Basin (Guangxi, China). Quatern. Int. 281, 5e9. Johnson, T.H., 1965. Flow instabilities relating to the surface markings of tektites. J. Geophys. Res. 71, 945e949. Koeberl, C., 1994. Tektite origin by hypervelocity asteroidal or cometary impact: Target rocks, source craters, and mechanisms. In: Dressler, B.O., Grieve, R.A.F., Sharpton, V.L. (Eds.), Large Meteorite Impacts and Planetary Evolution. Geological Survey of America Special Paper 293, Boulder, pp. 133e151. Koeberl, C., Glass, B.P., 2000. Tektites and the age paradox in mid-Pleistocene China. Science 289, 507a. LaMarche, P.H., Rauch, F., Lanford, W.A., 1984. Reaction between water and tektite glass. J. Non-Crystal. Solids 67, 361e369. Langbroek, M., 2015. Do tektites really date the bifaces from the Bose (Baise) Basin, Guangxi, southern China? J. Hum. Evol. 80, 175e178 [NEWS & VIEWS COMMENT PAIRED WITH THIS ONE]. Li, D.W., Wang, W., Feng, T., Wei, L., Bae, C.J., 2014. The oldest bark cloth beater in southern China (Dingmo, Bubing basin, Guangxi). Quatern. Int. (in press). Lycett, S.J., Bae, C.J., 2010. The Movius Line and Old World Palaeolithic patterns: the state of the debate. World Archaeol. 42 (4), 521e544. Lycett, S.J., Norton, C.J., 2010. A demographic model for Palaeolithic technological evolution: the case of East Asia and the Movius Line. Quatern. Int. 211, 55e65. Mazer, J.J., Bates, J.K., Bradley, J.P., Bradley, C.R., Stevenson, C.M., 1992. Alteration of tektites to form weathering products. Nature 357, 573e576. Norton, C.J., Bae, K.D., Harris, J.W.K., Lee, H.Y., 2006. Middle Pleistocene handaxes from the Korean Peninsula. J. Hum. Evol. 51, 527e536. O'Keefe, J.A., 1967. Tektites sculpturing. Geochim. Cosmochim. Acta 31, 1931e1933. Potts, R., Huang, W., Hou, Y., Deino, A., Yuan, B., Guo, Z., Clark, J., 2000. Response to “Tektites and the Age Paradox in Mid-Pleistocene China”. Science 289, 507a. Rost, R., 1969. Sculpturing of Moldavites and the problem of micromoldavites. J. Geophys. Res. 74, 6816e6824. Shoemaker, E.M., Uhlherr, H.R., 1999. Stratigraphic relations of australites in the Port Campbell Embayment, Victoria. MeteorPlanet. Sci. 34, 369e384. Wang, W., Mo, J.Y., Huang, Z.T., 2008. Recent discovery of handaxes associated with tektites in the Nanbanshan locality of the Damei site, Bose basin, Guangxi, South China. Chin. Sci. Bull. 53, 878e883. Wang, W., Bae, C.J., Huang, S.M., Huang, X., Tian, F., Mo, J.Y., Huang, Z.T., Huang, C.L., Xie, S.W., Li, D.W., 2014. Middle Pleistocene bifaces from Fengshudao (Bose Basin, Guangxi, China). J. Hum. Evol. 69, 110e122. Xu, G.L., Wang, W., Bae, C.J., Huang, S.M., Mo, Z.M., 2012. Spatial distribution of Paleolithic sites in Bose Basin, Guangxi, China. Quatern. Int. 281, 10e13.
Contents lists available at ScienceDirect
Journal of Human Evolution journal homepage: www.elsevier.com/locate/jhevol
News and views
How old are the Bose (Baise) Basin (Guangxi, southern China) bifaces? The Australasian tektites question revisited Wei Wang a, *, Christopher J. Bae b, * a b
Guangxi Museum of Nationalities, Nanning, Guangxi 530022, China Department of Anthropology, University of Hawai'i at Manoa, 2424 Maile Way, 346 Saunders Hall, Honolulu, HI 96822, USA
a r t i c l e i n f o Article history: Received 8 July 2014 Accepted 27 October 2014 Available online 3 December 2014
Introduction The age of the Bose Basin bifaces has long been debated in palaeoanthropology (e.g., Hou et al., 2000; Koeberl and Glass, 2000; Potts et al., 2000). In light of our recent article published in this journal (Wang et al., 2014), Langbroek (2015) raises similar questions about the association of the Australasian tektites and the Bose Basin bifaces that were mentioned earlier by Koeberl and Glass (2000). Langbroek's (2015) argument is based on two points: 1) using examples from mainland Southeast Asia, he suggests there is ample or strong evidence of vertical displacement of the tektites; and 2) he questions our interpretation of the tektite surface morphology to argue against in situ deposition of the tektites. We address each of these points in turn. Vertical displacement of the tektites Langbroek (2015) argues that the depositional sequence of Bose is similar to other areas of the Australasian strewnfield (e.g., Thailand, Laos, Vietnam). Citing works by Fiske et al. (1996, 1999) from Southeast Asia, Langbroek concludes that the sedimentary sequence in Bose is the result of reworking and is nothing more than a lag deposit that contains materials of different ages, including from the Holocene, as is apparently the case for many sites in mainland Southeast Asia. In our opinion, the Bose Basin tektites are geomorphologically, stratigraphically and sedimentologically different from the
* Corresponding authors. E-mail addresses: [email protected] (W. Wang), [email protected] (C.J. Bae). http://dx.doi.org/10.1016/j.jhevol.2014.10.013 0047-2484/© 2014 Elsevier Ltd. All rights reserved.
Southeast Asian examples cited by Langbroek. At least five fluvial terraces developed in the Bose Basin, with the tektites overwhelmingly appearing in the laterite of the upper part of terrace 4 (‘T4’). To date, there are only two exceptions to this: two abraded slightly rounded tektites were found in the gravel bed in T3 in the central part of the basin (Fig. 1, the left and middle tektites in the bottom row) and one heavily abraded tektite was found in the lower reaches of the Youjiang River (Fig. 1, the right tektite in the bottom row) (Wang et al., 2008). Terrace 4 is the most typical river terrace with the largest distribution in the basin. The T4 sequence is extremely stable, consisting of upper laterite (5e10 m in thickness) and an underlying gravel bed (2e10 m in thickness). This sequence is evident throughout the basin in numerous exposed and excavated profiles. Terrace 4 strata can be clearly divided into four units from top to bottom: Unit-1, brown surface loess-like deposit, distributed only in a few well-preserved platforms, unconformity with underlain laterite, 20e40 cm in thickness; Unit-2, red sandy-clay (laterite), containing stone artifacts occasionally, 1e3 m in thickness; Unit-3, reticular mottled red clay, containing typical stone artifacts, tektites are located in the middle of this unit, 4e6 m in thickness; Unit-4, grey gravel bed, well-sorted, 2e10 m in thickness (Fig. 2). Unit-1 is thin, and obviously distinguishes from the underlying Unit-2. A distinct boundary does not exist between Unit-2 and Unit3, which display transitional features. The different characteristics of Unit-2 and Unit-3 are probably due to variation in exposure to weathering, with the latter unit more severely affected. The tektite layer is concentrated in the middle of Unit-3, the reticular mottled red clay. Unit-3 is homogeneous, with no evidence of a paleoerosional surface. There is no evidence from the T4 profiles of marked vertical redeposition or the mixing of materials from different temporal periods and/or cultural units. The Bose Basin stratigraphy is not similar to the Southeast Asian sites cited by Langbroek. It should be noted that Langbroek (2015) has suggested that Figure 3 from the Nanbanshan locality in Damei (Wang et al., 2008) can be used as evidence that much of the deposits in Bose were subjected to vertical reworking with artifacts from T2 and T3 being moved to T4. Unfortunately, Langbroek has misread the stratigraphic profile from the Nanbanshan site. In the Wang et al. (2008: 878) study, it was specifically stated that “[t]he Nanbanshan locality of the Damei
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Figure 1. To date, only three of the more than 275 tektites found in Bose were recovered from T3. The first two rows present typical tektites from T4, while the bottom row presents the three abraded and worn tektites recovered from T3.
site (23 46.6640 N,106 43.7200 E) is located on terrace 4 of the Youjiang River in the southeast Youjiang district of Bose City (Fig.1).” (emphasis added). Nowhere in the Wang et al. (2008) paper is it stated that T2 and T3 are found overlying T4 at the Nanbanshan site. In fact, if that were the case, the deposits would be many tens of meters thick. The stratigraphic profile presented in Figure 3 from Wang et al. (2008) of that paper represents only deposits from T4. Thus, Langbroek's interpretation of the Nanbanshan stratigraphy is unwarranted. Nevertheless, if vertical reworking of the various strata in Bose is the most parsimonious explanation to rationalize the association of
the Australasian tektites and the bifaces, we ask the following questions then: 1) Why do the bifaces only appear in T4? 2) Why is there a paucity of evidence of hominin occupation in T3 and T2? 3) Why are there clear Neolithic occupations only in T1? If Langbroek (2015) is correct that the examples from mainland Southeast Asia are equally applicable to the Chinese case and the Bose materials are extensively reworked vertically, we should expect to find Neolithic artifacts (e.g., pottery, ground stone tools) appearing, minimally in T4 in association with the supposedly younger handaxes and older tektites. However, this does not appear to be the
Figure 2. This photograph is taken at Gaolingpo, a recently excavated (2014) Paleolithic site in eastern Bose Basin. Units 1 to 3 are presented, the underlying Unit-4 is not shown.
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case. For researchers familiar with the Chinese Paleolithic and Neolithic, there are noticeable differences between the types and morphologies of artifacts found in Early Paleolithic and Neolithic sites in Guangxi (e.g., compare the artifacts from Wang et al., 2014; Li et al., in press). After more than four decades of research in Bose, primarily by Chinese scientists but also in collaboration with American researchers (e.g., R. Potts, C.J. Bae), such a mixed deposit of Neolithic and Early Paleolithic artifacts has yet to be identified. Because Neolithic artifacts have failed to systematically appear in other terraces (e.g., T2eT4) in the basin (and vice-versa for the bifaces and tektites), we question Langbroek's argument that the depositional sequence in Bose (and purported reworking of the deposits) is the same as that which appears in mainland Southeast Asia. Further, Langbroek (2015) raises the possibility that availability or non-availability of raw materials may explain the absence of stone tools in the upper terraces. However, as we noted in our original paper (Wang et al., 2014), the hominins occupying the Bose Basin were clearly relying on locally- and readily-available raw materials. Because of possible lower population densities in eastern Asia during the Pleistocene (cf. Lycett and Norton, 2010), it is possible that the Bose Basin was sparsely occupied or even completely abandoned for long periods of time (see Huang et al., 2012; Xu et al., 2012 for variation in site distributions across the basin). This, in our opinion, is a more parsimonious explanation for the paucity of sites in T3 and T2 than arguing that the Bose hominins used T4 for certain activities and T3 and T2 for other activities, as suggested by Langbroek (2015). We are not the only ones to argue that in certain cases at least some of the Australasian tektites were found in situ. For instance, Shoemaker and Uhlherr (1999) identified a series of sites in Australia where the tektites did not likely move very far after landing. Haines et al. (2004) more recently identified at least one site in northeast Thailand where the tektites appear to be found in situ. Indeed, Haines et al. (2004: 26) note that “consistent with a very brief time period between impact and burial is the lack of abrasion on the tektites from unit A, implying very limited residence time in a high energy alluvial environment, or to exposure at the surface” (emphasis added). In fact, Haines et al.’s (2004) reflection does not differ significantly from our own observations of many of the Bose tektites that appear to lack any evidence of extensive abrasion (Wang et al., 2014). Other differences between other areas within the Australasian strewnfield and Bose exist as well. For instance, at the Uhlherr's Good Spot in Australia, more than 260 tektites were collected in an area <80 m in length and ~30 m in width (Shoemaker and Uhlherr, 1999; see also Fiske et al., 1996, 1999 for discussion of high tektite densities in Southeast Asia). Although we have not conducted a systematic investigation of tektite densities in the Bose Basin, it would appear to be far lower than comparably sized regions in mainland Southeast Asia and Australia. To date, only about 275 tektites have been found throughout the entire Bose Basin. In addition, the overall size of individual tektites appears to be significantly different. Indeed, Fiske et al. (1999) note that one Southeast Asian fragmented mass alone may have originally weighed as much as 1000 kg. The Bose Basin tektites are fist-sized and smaller. The lower tektite density and sizes in Bose would in fact not be all that surprising given the fact that Guangxi is considered the northernmost extension of the Australasian tektite distribution. Tektite surface morphology More than 50 years ago, Chapman and Larson (1963) reviewed a wide diversity of hypotheses that have been proposed to explain
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the origin of, and related to this current debate, the morphology of the tektites. The debate regarding the morphology of tektites can be broadly grouped into two camps: 1) predepositional aerodynamic explanations, and 2) postdepositional chemical erosion explanations. Langbroek (2015) cites a number of studies (e.g., Rost, 1969; Lamarche et al., 1984; Barnes, 1990) that not surprisingly fall in the latter camp and is used to support his argument that we misunderstand the true meaning of the morphology of the tektites (in our original paper, we argued for predepositional aerodynamic modification and minimal postdepositional movement). However, it should be noted that there are a number of other studies (e.g., Chapman et al., 1962; Chapman and Larsen, 1963; Johnson, 1965; O'Keefe, 1967) that were not cited by Langbroek, but in fact support the predepositional aerodynamic explanation. For instance, hypervelocity ablation experiments in the laboratory have reproduced the same surface sculptures, geometric shapes, systematic striae distortions, and coiled circumferential flanges as those found on tektites from Australia (Chapman and Larson, 1963). In any case, the moldavites from Central Europe are often cited as the primary evidence of tektite chemical erosion (e.g., Rost, 1969; Langbroek, 2015). However, the Central European moldavites are ~14.5 Ma (millions of years ago) and the Australasian tektites date to no more than 803 ka (thousands of years ago). Even if chemical erosion is a major influence in the morphology of the 14.5 Ma moldavites, it may be possible that not enough time has passed for that process to have had a significant influence on the Australasian tektites. Only experimental studies specific to the Australasian tektites would be able to verify or refute the hypothesis that the morphology of these tektites is a direct result of chemical erosion (see, for example, Barkatt et al., 1984, 1986, 1989; Mazer et al., 1992). In relation to our own analysis and interpretation of the Australasian tektites that are present in Bose, there does not appear to be anything blatantly incorrect with what we said in our original study (contra Langbroek, 2015). If anything, as earlier studies have argued (e.g., Potts et al., 2000) and as we note here and elsewhere (Wang et al., 2014), there appears to be relatively little movement of the tektites postdepositionally (either laterally or vertically) (see also Shoemaker and Uhlherr, 1999; Haines et al., 2004 for similar examples in other regions of the Australasian strewnfield). Needless to say, concluding that the predepositional aerodynamic argument makes sense in explaining the morphology of the Bose tektites should not be equated with arguing for the now disproven hypothesis that all tektites are of lunar origin (for review see Koeberl, 1994). We are simply using the Bose tektite morphology to suggest that the tektites have not been significantly moved from a different terrace, particularly because the Bose tektites are so restricted to one specific terrace, a situation that appears to differ fairly clearly from many other regions of Southeast Asia and Australia. Discussion Although Langbroek (2015) recommends that we try other dating methods to crosscheck the age of the Bose Basin sites and materials, it should be noted that we have already made some attempts. For instance, Deng et al. (2007) conducted a paleomagnetic analysis of the sedimentary sequence from the Damei site. Unfortunately, because of strong chemical weathering that occurs due to the subtropical condition in southern China a chemical remanent magnetization overprint is sufficiently strong to mask the primary natural remanent magnetization. The Deng et al. (2007) study indicated that magnetostratigraphic studies on red soil sequences in subtropical and tropical southern China should be interpreted with great caution. More recently, Guangjun Shen, Darryl Granger, and colleagues have been searching the Bose Basin's fourth terrace
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for areas that are over 10 m thick in order to attempt a cosmogenic 26 Al/10Be burial dating analysis of the quartz sediments (Personal communication from G.J. Shen). As noted above, there are a series of differences between the Bose Basin and mainland Southeast Asia and Australia situations, which would suggest they are not exactly comparable and should be treated differently. In addition, the argument for chemical etching, particularly using the examples of the 14.5 Ma Central European moldavites, to refute minimal postdepositional movement of the Bose tektites is not, in our opinion, very strongly supported. Future experimental studies that focus on the Australasian tektites could potentially shed light on the rate of chemical erosion and what other variables would need to be factored in. Nevertheless, the Bose Basin tektites are clearly concentrated in the reticular mottled red clay of T4, with only two examples of wellrounded and abraded tektites appearing in T3. There is little evidence of vertical movement of the materials (e.g., we do not find Early Paleolithic bifacial implements mixed in the same stratigraphic layers as Neolithic pottery sherds and ground stone tools). If anything, assuming the Early Paleolithic bifaces originated from T4 and the tektites moved vertically from T3 or T2, then in fact, by default this would make the Bose bifaces older than the EarlyMiddle Pleistocene transition. Because of the high concentration of Early Paleolithic stone tools and tektites in a restricted sequence of T4, we are not going to make that argument. However, it is interesting if one reversed the argument and tried to make the case that the stone tools are in original deposition and the tektites moved vertically from an overlying terrace (this is something that could be read from the Koeberl and Glass, 2000 paper). Just some food for thought as the true meaning of the Bose tektites continues to be discussed. The nature of the Movius Line will likely continue to be debated (e.g., Hou et al., 2000; Norton et al., 2006; Lycett and Bae, 2010; Lycett and Norton, 2010) and understanding the age of the eastern Asian bifaces contributes an important part to deciphering the true meaning of the line. We sincerely appreciate scientists raising questions about the depositional history of the Australasian tektites in the Bose Basin and their relationship to the bifaces. However, until proven otherwise “anything found in T4 can be confidently associated with the tektites” (Wang et al., 2014: 116). Acknowledgements Funding for this research is from the 2014 University of Hawai'i at Manoa College of Social Sciences Research Award. The initial draft of this response was written while we were out in the middle of fieldwork in Guangxi, China. We thank Kathryn Burns, based in Hawai'i at the time, who was able to track down some of the more difficult-to-find references for us on short notice. We appreciate the comments from Christian Koeberl and an anonymous reviewer that helped to tighten up the text. We take full responsibility for any errors that may be present. References Barkatt, A., Boulos, M.S., Barkatt, Al., Sousanpour, W., Boroomand, M.A., Macedo, P.B., O'Keefe, J.A., 1984. The chemical durability of tektites-A laboratory
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