Journal of Archaeological Science 34 (2007) 2109e2114
http://www.elsevier.com/locate/jas
Mass spectrometric U-series dating of Laibin hominid site
in Guangxi, southern China
Guanjun Shen a,*, Wei Wang b, Hai Cheng c, R. Lawrence Edwards c
a
College of Geographical Sciences, Nanjing Normal University, Nanjing 210046, PR China
Natural History Museum of Guangxi Zhuang Autonomous Region, Nanning 530012, PR China
c
Department of Geology and Geophysics, University of Minnesota, Minneapolis, MN 55455, USA
b
Received 13 September 2006; received in revised form 25 January 2007; accepted 25 February 2007
Abstract
The Laibin hominid represents one of the rare finds of modern Homo sapiens in China, rare for its relative completeness and well-established
stratigaphic provenance. This paper presents the results of mass spectrometric U-series dating of intercalated calcite samples from the Laibin
site. The capping flowstone and the calcite vein, which sandwich the hominid fossil-containing deposits, date to 38.5 1.0 and 44.0 0.8 ka,
setting respectively the minimum and maximum ages to the fossils. The second flowstone layer is 112.0 1.4 ka old, indicating that the cultural
sequence may possibly extend to somewhere between 44 and 112 ka. Securely dated Laibin finds should be of importance in reconstructing
human physical and cultural evolution in the region.
Ó 2007 Elsevier Ltd. All rights reserved.
Keywords: Laibin hominid; Morphologically modern humans; U-series dating; Speleothem calcite; Late Pleistocene; Southern China
1. Introduction
Qilinshan Hill is located at ca. 1.5 km north of Qiaogong
Town in Laibin County, Guangxi Zhuang Autonomous Region, southern China (Fig. 1). This isolated peak of Permian
limestone, which forms the characteristic landscape of the region, is ca. 45 m in height, and ca. 150 m east to west and ca.
110 m south to north. Its basement rock has experienced extensive karstic processes, resulting in numerous caves, some
filled with fossil-containing detrital sediments.
Gaitou cave (23 430 3500 N, 109 050 2900 E) is situated at the
southern slope of the hill. The cavern is ca. 7 m above the present ground surface with an entrance facing south, ca. 2.7 m high
and ca. 1.3 m wide. In January 1956, a field team led by the late
archaeologist Lanpo Jia carried out a test excavation in the cave.
A fragmentary hominid skull base was recovered together with
tooth fragments of Cervus and Sus and a considerable amount
* Corresponding author. Tel.: þ86 25 85891829; fax: þ86 25 85891347.
E-mail address: [email protected] (G. Shen).
0305-4403/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.jas.2007.02.008
of freshwater shells. Three lithic artifacts and a thin ash layer
containing burnt bones were also found (Jia and Wu, 1959;
Wu and Poirier, 1995).
The Laibin specimen consists of three disconnected pieces:
a nearly complete hard palate with several teeth and the adjoining lower part of the body of the maxilla, a large part of
the right zygomatic and an occipital fragment, which are all
grayish-white in color and moderately fossilized. Based on
morphological studies, Jia and Wu (1959) concluded that
‘‘for lack of distinct archaic features, the hominid fossils
from Qilinshan Hill should be taken as modern Homo sapiens’’. This attribution has been widely cited in the literature
(e.g., Wu and Poirier, 1995).
For about two decades, the time and location of the origin
of modern H. sapiens has been the subject of an intensive debate mainly between the exponents of two competing hypotheses, ‘‘regional continuity’’ (e.g., Wolpoff et al., 1984, 2001)
and ‘‘recent out of Africa’’ (e.g., Stringer and Andrews,
1988; White et al., 2003). The accurate dating of relevant finds
is key to addressing the controversial issues.
2110
G. Shen et al. / Journal of Archaeological Science 34 (2007) 2109e2114
Fig. 1. Map showing the location of Gaitou cave, the burial site of Laibin hominid and neighboring hominid localities, Tongtianyan, Bailiandong, Ganqian and
Dalongtan, which are discussed in the text.
The validity of the U-series dating of pure and dense cave
calcites has been well demonstrated (e.g., Ludwig and Renne,
2000; Richards and Dorale, 2003; Schwarcz, 1992). Mainly
with this chronometer we have, in recent years, studied a number of modern H. sapiens localities in southern China, those in
Guangxi including Liujiang (Shen et al., 2002b), Ganqian
(Shen et al., 2001a) and Bailiandong (Shen et al., 2001b)
caves. The results demonstrate that these sites, previously
estimated at 20e30 ka, should be earlier Late Pleistocene in
age, certain lower horizons may even be later Middle Pleistocene. The possibility of a much earlier appearance of modern
H. sapiens in China than previously estimated will impact profoundly on the afore-mentioned debate.
However, the above dating results also point to the necessity of further studies. The reason for this is that the Liujiang
skull, though quite complete, is an amateur recovery. Its exact
stratigraphic provenance can hardly be unequivocally fixed.
This explains the general reluctance of the paleoanthropology
community to accept the age dating, although we deem that
the inferences involved in arriving at the new age assignments
should be highly rational. At other sites we have studied, hominids are mostly known through isolated teeth, so their
phylogenetic position cannot be assuredly defined. Moreover,
the re-assignment of the above-mentioned sites to around
100 ka not only contrasts strongly with the previously accepted time-scale, but also leaves an important gap in the
sequence of human occupation. To address these issues, we
have been searching for more modern H. sapiens sites suitable
for chronological studies.
Laibin hominid came to our attention because it was found
in the course of a well-organized excavation and from a wellestablished stratigraphic position, i.e. some 0.12 m below the
capping flowstone (Jia and Wu, 1959). Moreover, judging by
previous publications (Jia and Wu, 1959; Wu and Poirier,
1995), in spite of their incompleteness the hominid fossils
are diagnostically significant to represent modern H. sapiens.
Similar finds are rare among the inventory of fossil hominids
in China. Thus precise dating of this specimen should be of
importance. However, apart from relative age estimate at
a late Paleolithic stage, no radiometric dating has ever been
performed.
Jia and Wu (1959) reported that the fossiliferous deposits of
the site were interbedded with flowstone layers. We confirmed
the existence of intercalated speleothem formations in the
G. Shen et al. / Journal of Archaeological Science 34 (2007) 2109e2114
course of a field investigation. Several calcite samples were
taken then and trial U-series measurements performed with
classical alpha spectrometry. However, due to detrital contamination as reflected in rather low 230Th/232Th activity ratios,
the results suffer from major uncertainty. To circumvent the
difficulty, the raw samples were closely examined and it was
found that thin sub-layers of quite pure and dense calcite exist
in several of them. The purer portions were carefully picked
out and analyzed with high precision inductively coupled
plasma mass spectrometry (ICP-MS), yielding U-Th dates
with much improved reliability. Subsequent fieldwork enabled
collection of several more small (gram or sub-gram) and,
therefore, purer samples. In this paper we present the U-series
results of these samples and discuss their implications for human physical and cultural evolution in the region.
2. Samples in stratigraphic context
The ca. 10-m deep cave consists of three parts: Outer Corridor, Inner Corridor and East Branch Corridor (Fig. 2). In the
Outer Corridor only about 3 m3 of deposits near the eastern
wall survived fertilizer mining, of which about 1 m3 was consumed by the test excavation in 1956 (Jia and Wu, 1959). The
deposits inside the East Branch Corridor, consisting of brownish loose clay containing a few fossils, were almost completely
dug out by the fertilizer miners. In contrast, about half of the
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deposits in the Inner Corridor remain intact, probably owing to
the protection of a thick capping flowstone. The disturbed
portions there show that the deposits under the capping flowstone are composed of brownish loose clay, containing some
gravels but no fossils or shells. The present work is concentrated on the extant cross-section near the eastern wall in the
Outer Corridor (line AB in Fig. 2), which is now represented
by less than 1 m3 of deposits as the result of natural weathering processes.
Jia and Wu (1959) gave a brief stratigraphic description, in
which the depositional sequence was divided into two layers:
a lower layer of consolidated red loam and an upper layer of
slightly consolidated yellowish gray breccia. The upper layer
was further divided into three sub-layers by intercalated thin
flowstones. Having performed in situ stratigraphic studies,
we deem it pertinent to redescribe the depositional sequence
in more detail and to divide it into the following four layers
(Fig. 3, numbers from top to bottom).
1. Capping flowstone, ca. 10 cm thick, brownish white, consisting of 3e5 sub-layers.
2. Sandy clay, 70e115 cm thick, brownish, moderately consolidated, containing fossils and gravels, shell-bearing except for the lowest ca. 20 cm. The deposits are intercalated
with several thin and heavily muddy flowstone layers of
limited extent. Its middle to lower sections are intersected
by a calcite vein, presumably resulting from a partial
washing-out and re-deposition event. Although no depositional hiatus is obvious, whether the lowermost shell-lacking deposits contain any trace of human activity remains
unclear.
3. Second flowstone layer, 1e3 cm thick, brownish white.
4. Sandy clay, an exposed section of 40e60 cm with unknown total thickness, brownish, strongly consolidated,
sterile, gravel-bearing.
Samples QLS-6 and 7 were taken from localized 1e2-mm
thick pure sub-layers of the capping flowstone, while QLS11 was taken from an overlying small stalagmite. QLS-12
and 16 represent the purest possible sub-layers of the calcite
vein in Layer 2. QLS-9 was collected from the second flowstone layer, enclosed in which a tiny piece (ca. 0.2 g) of fossil
bone was taken as QLS-5. QLS-17 is a fragment of deer tooth
ca. 20 cm below the capping flowstone. The samples’ stratigraphic positions are shown in Fig. 3. It should be noted
here that to avoid post-depositional calcite in small erosional
cavities, only the purest possible portions with clear laminae
and natural contact with their less pure surroundings were
picked out for dating.
3. Dating results
Fig. 2. Plane figure of Gaitou cave, showing the position of the Outer Corridor,
Inner Corridor and East Branch Corridor. The present study is concentrated on
the extant cross-section (line AB) near the eastern wall, where the hominid
fossils were recovered in course of the test excavation in 1956.
The samples’ 230Th/234U dates were determined with ICPMS (Finnegan Element) at the Minnesota Isotope Laboratory,
University of Minnesota, USA except for QLS-5 and the dentine of QLS-17 which were measured with classical alpha
spectrometry at the first author’s laboratory in Nanjing. The
G. Shen et al. / Journal of Archaeological Science 34 (2007) 2109e2114
2112
Fig. 3. Sketch showing the preserved cross-section, corresponding to the line AB in Fig. 2. Samples for dating were collected from three speleothem horizons:
capping flowstone, second flowstone and a calcite vein running from middle to lower sections of Layer 2. A sectional view of the calcite vein is given in the upper
right inset.
analytical procedure for ICP-MS measurements is shown in
Shen et al. (2002a). The instrumental bias correction, 230Th
and 234U half lives, standards and spikes used in age determinations are as discussed in Cheng et al. (2000). U-Th isotopic
ratios and derived age results are presented in Table 1.
In spite of our great carefulness in sample collection and
pretreatment, the calcite specimens for ICP-MS determinations are still not sufficiently pure. This is shown by the
230
Th/232Th ratios between 5.4 and 31.1, which are not as
high as expected. Nevertheless, for each of the three speleothem horizons, we have one 230Th/232Th ratio greater than
Table 1
Mass spectrometric U-Th isotopic ratios and
15, high enough to ensure the reliability of the dates obtained.
The general consistency between coeval samples with higher
or lower 230Th/232Th ratios lends support to their reliability.
The very young age of QLS-6 (7.9 0.2 ka) indicates
recent speleothem formation in the cave. As the sample is
located at the surface, no meaningful age constraint can be
inferred from this date.
QLS-7 and 11 from the capping flowstone yield dates consistent within errors with a weighted mean of 38.5 1.0 ka.
Duplicated analyses on QLS-12 and 16 from the calcite vein
all give consistent results with a weighted mean of
230
Th age results
Sample number
238
230
234
230
230
Th age (ka)
(corrected)
QLS-6
QLS-7
QLS-11
QLS-12
QLS-12
QLS-16
QLS-16
QLS-9
QLS-17
QLS-17
QLS-5a
0.4461 0.0006
0.7557 0.0009
0.3200 0.0005
0.2180 0.0003
0.2892 0.0003
0.3135 0.0004
0.3012 0.0004
0.4753 0.0008
6.525 0.013
54.5
29.3
8.3 0.2
5.4 0.1
15.5 0.1
10.3 0.1
15.8 0.1
9.5 0.1
12.3 0.1
31.1 0.2
667 10
53.9
229.9
1.0284 0.0015
0.9204 0.0013
1.0366 0.0015
1.0500 0.0013
1.0341 0.0014
1.0269 0.0013
1.0275 0.0016
1.0377 0.0017
1.0516 0.0015
1.035 0.034
1.182 0.022
0.0873 0.0015
0.3061 0.0065
0.3207 0.0023
0.3445 0.0026
0.3570 0.0024
0.3718 0.0036
0.3540 0.0033
0.6755 0.0035
0.1019 0.0004
0.131 0.012
0.537 0.020
9.7 0.2
44.4 1.2
40.3 0.4
43.3 0.4
46.1 0.4
48.9 0.6
46.0 0.5
113.8 1.1
11.1 0.5
15 2
82 4
7.9 0.2
38.7 3.2
38.5 1.0
40.4 2.9
44.2 1.1
45.5 1.8
43.5 1.4
112.0 1.4
(I)
(II)
(I)
(II)
(enamel)
(dentine)a
U (ppm)
Th/232Th
U/238U
Th/238U
Th age (ka)
230
*All isotopic ratios are in activity, errors 2s. Decay constants used: l230 ¼ 9.1577 106 year1, l234 ¼ 2.8263 106 year1. Corrected 230Th ages assume the
initial 230Th/232Th atomic ratio of 4.4 2.2 106, a value for a material with the bulk earth 232Th/238U atomic ratio of 3.8 at secular equilibrium, with an
arbitrarily assumed error of 50%. The dates in bold are cited in the text.
a
Measured with alpha spectrometry at the first author’s laboratory in Nanjing.
G. Shen et al. / Journal of Archaeological Science 34 (2007) 2109e2114
44.0 0.8 ka. As the hominid specimen was recovered from
the deposits in-between, its age can be securely bracketed
between 39 and 44 ka. The date on QLS-9 indicates that the
second flowstone layer formed 112.0 1.4 ka ago, thus giving
a maximum age to the overlying deposits. It should be noted
here that due to the highly episodic deposition in caves and
to the presence of an intervenient shell-lacking sub-layer, human occupation of the site may happen substantially later than
the maximum age defined by the underlying flowstone layer.
The deer tooth fragment QLS-17 comes from about the same
horizon as the hominid fossils. Its enamel and dentine give
broadly consistent dates of 11.1 0.5 and 15 2 ka respectively, much younger than indicated by the correlated flowstone
layers. The bone fragment QLS-5 (82 4 ka) is also much
younger than its encasing calcite (112.0 1.4 ka). These results are in line with our previous studies, which indicate that
fossil bones are susceptible to post depositional U migration,
leading generally to underestimated dates in a cave setting
(Shen, 1996).
4. Discussion and conclusion
In contrast to the hot debate about the origin of modern H.
sapiens, only a small number of securely dated fossils are
available for reconstructing recent human evolution in Africa
(Shea and Fleagle, 2005). The situation should be about the
same in China, if not worse, where only a small proportion
of the relevant sites have been numerically dated. Classical
14
C and U-series determinations on fossil materials remain
the most utilized chronometers, both however are known for
limited reliability (Shen, 1996; Taylor, 1992). Besides, up to
a few years ago important representatives of modern H. sapiens in China were all dated to less than 30 ka, and apparently
there is a time gap of human presence between 40 and 100 ka
(Stringer, 1988). Under such circumstances, a tight assignment
of 39e44 ka to Laibin hominid bears important implications.
First, the present results contribute a midpoint to the sequence of Late Pleistocene human evolution in the region.
Laibin hominid represents modern people in craniofacial morphology. In neighboring areas there are three older hominid
finds. The Liujiang skull is reported to be at least 68 ka old,
most probably between 111 and 139 ka and possibly still older
(Shen et al., 2002b). The Tubo hominid, represented by 17
fossil teeth, is bracketed in the range of 94 and 220 ka (Shen
et al., 2001a). At Bailiandong an overlying flowstone layer
sets a minimum age of 160 ka to the two hominid teeth (Shen
et al., 2001b). Four more or less complete human skeletons recovered from the Dalongtan site represent younger specimens,
to which 14C dating of charcoal grains assigned an age of
ca. 10 ka (Zhou and Zhang, 1994). The pattern of human
evolution will be clarified with the increasing number of
reliably dated hominid finds.
Second, except for the lowermost w20 cm the Layer 2 deposits are quite rich in freshwater shells, most of them of the
species of Viviparus and Semisulcospira. To have an idea
about the density, we arbitrarily chose an area of 50 by
50 cm and counted 63 shells. Shellfish gathering is widely
2113
accepted as an archaeological indication of modern behavior
(Broadhurst et al., 2002). If finally proved to be the result of
human activity, the shells buried in the deposits assuredly
dated to older than 44 ka may represent the yet earliest record
of systematic mollusk exploitation in China.
Third, according to the previous temporal framework, no
hominid remains in China are securely dated to the range of
40e100 ka (Stringer, 1988). Proponents of the out-of-Africa
model consider that this marks an interruption when the
aboriginal populations (H. erectus or archaic H. sapiens) in
East Asia had died out and the oncoming African modern people were still on the way (e.g., Jin and Su, 2000). The hominid
remains, stone artifacts and molluscan shells recovered from
Gaitou cave, dated reliably to the range of 39e44 ka and possibly to somewhere between 44 and 112 ka, may be cited as
a supporting evidence for an inhabited southern China during
this time interval. This is in line with recent discoveries of
stone artifacts in the deposits dated to w70 ka at Jingshuiwan
in Chongqing (Pei et al., 2006) and to 55e110 ka in Zhangkou
cave, Yunnan Province (Shen et al., 2005). The so-called fossil
gap is likely nothing but an artifact due to systematic errors of
dating techniques and should be further explored.
In conclusion, Laibin hominid dates to the range of 39e
44 ka, while the cultural sequence of the site may possibly
extend to somewhere between 44 and 112 ka. The present
study marks one step forward in our effort to establish an
integrated chronological sequence for recent human evolution
in China. Further studies to date more modern hominid fossils
are currently under way. Southern China provides a promising
ground for research in this direction, as the region abounds in
Late Pleistocene hominid sites in limestone caves, where
cultural/fossiliferous deposits are often intercalated with speleothem formations. With the possibility of stringent temporal
constraints, the hominid finds there will contribute fundamentally to elucidating the much-debated issues concerning the
origin, dispersal and evolution of modern H. sapiens.
Acknowledgements
This project has been jointly supported by National Natural
Science Foundation of China (40373031) and WennerGren Foundation (Gr. 6975). ICP-MS U-series analyses were
supported by US NSF grants. We thank the government of
Guangxi Zhuang Autonomous Region for permission, Dr
James L. Bischoff and Dr Qian Wang for helpful discussions
and two anonymous referees for constructive criticisms that
improved clarity and consistency. The first author is thankful
to his graduate students Li Shi and Xinfeng Zhang for sample
pretreatment and alpha spectrometric determinations.
References
Broadhurst, C.L., Wang, Y.Q., Crawford, M.A., Cunnane, S.C.,
Parkington, J.E., Schmidt, W.F., 2002. Brain-specific lipids from marine,
lacustrine, or terrestrial food resources: potential impact on early African
Homo sapiens. Comparative Biochemistry and Physiology Part B 131,
653e673.
2114
G. Shen et al. / Journal of Archaeological Science 34 (2007) 2109e2114
Cheng, H., Edwards, R.L., Hoff, J., Gallup, C.D., Richards, D.A.,
Asmerom, Y., 2000. The half-lives of uranium-234 and thorium-230.
Chemical Geology 169, 17e33.
Jia, L.P., Wu, J.K., 1959. Fossil human skull base of late Paleolithic stage from
Chilinshan, Leipin District, Kwangsi, China. Paleovertebrata et Paleoanthropologica 1 (1), 16e18 (in Chinese).
Jin, L., Su, B., 2000. Natives or immigrants: modern human origin in East
Asia. Nature Reviews Genetics 1, 126e133.
Ludwig, K.R., Renne, P.R., 2000. Geochronology on the Paleoanthropological
time scale. Evolutionary Anthropology 9 (2), 101e110.
Pei, S.W., Zhang, J.F., Gao, X., Zhou, L.P., Feng, X.W., Chen, F.Y., 2006.
Optical dating of the Jingshuiwan Paleolithic site of Three Gorges, China.
Chinese Science Bulletin 51 (11), 1334e1342.
Richards, D.A., Dorale, J.A., 2003. Uranium-series chronology and environmental applications of speleothems. Reviews in Mineralogy and Geochemistry 52, 407e460.
Schwarcz, H.P., 1992. Uranium-series dating and the origin of modern man.
Philosophical Transactions of the Royal Society of London B 337,
131e137.
Shea, J.J., Fleagle, J.G., 2005. Origin of modern humans on Long Island.
Evolutionary Anthropology 14, 86e87.
Shen, C.-C., Edwards, R.L., Cheng, H., Dorale, J.A., Thomas, R.B.,
Moran, S.B., Weinstein, S., Edmonds, H.N., 2002a. Uranium and thorium
isotopic and concentration measurements by magnetic sector inductively
coupled plasma mass spectrometry. Chemical Geology 185, 165e178.
Shen, G.J., 1996. U-series dating of fossil bones: results from Chinese sites
and discussion on its reliability. Chinese Journal of Geochemistry 15,
303e313.
Shen, G.J., Wang, W., Wang, Q., Pan, Y.J., 2001a. U-series dating of hominid
site Ganqian cave at Tubo, Liujiang, Guangxi in South China. Acta
Anthropologica Sinica 20 (3), 238e244 (in Chinese, with English
abstract).
Shen, G.J., Wang, J.Q., Xu, B.X., Kuang, Y., Zhao, J.X., 2001b. U-series
dating of Bailiandong site in Liuzhou, Guangxi, South China. Journal of
Stratigraphy 25, 325e330 (in Chinese, with English abstract).
Shen, G.J., Wang, W., Wang, Q., Zhao, J.X., Collerson, K., Zhou, C.L.,
Tobias, P.V., 2002b. U-series dating of Liujiang hominid site in Guangxi,
southern China. Journal of Human Evolution 43 (6), 817e829.
Shen, G.J., Li, J.K., Ji, X.P., 2005. U-series dating of Zhangkou Cave in
Yiliang, Yunnan Province: evidence for human activities in China during
40 and 100 ka. Chinese Science Bulletin 50 (4), 355e359.
Stringer, C.B., 1988. The dates of Eden. Nature 331, 565e566.
Stringer, C.B., Andrews, P., 1988. Genetic and fossil evidence for the origin of
modern humans. Science 239, 1263e1268.
Taylor, R.E., 1992. Radiocarbon dating of bone: to collagen and beyond. In:
Taylor, R.E., Long, A., Kra, R.S. (Eds.), Radiocarbon after Four Decades,
an Interdisciplinary Perspective. Springer-Verlag, New York, pp. 375e402.
White, T.D., Asfaw, B., Degusta, D., Gilbert, H., Richards, G.D., Suwa, G.,
Howell, F.C., 2003. The Herto Pleistocene Homo sapiens from Middle
Awash, Ethiopia. Nature 423, 742e747.
Wolpoff, M., Wu, X.Z., Thorne, A., 1984. Modern Homo sapiens: a general
theory of hominid evolution involving the fossil evidence from east
Asia. In: Smith, F., Spencer, F. (Eds.), The Origins of Modern Humans.
Alan R. Liss, New York, pp. 411e483.
Wolpoff, M., Hawks, J., Frayer, D.W., Hunley, D.K., 2001. Modern human
ancestry at the peripheries: a test of the replacement theory. Science
291, 293e297.
Wu, X.Z., Poirier, F.E., 1995. Human Evolution in China. Oxford University
Press, New York.
Zhou, G.X., Zhang, Z.B., 1994. A study on remains of Liuzhou Dalongtan
Man of Mesolithic to early Neolithic. In: Zhou, G.X. (Ed.), International
Symposium on Relationship between Chinese and Japanese Ancient
Men and Prehistoric Cultures. China International Radio Press, Beijing,
pp. 59e88 (in Chinese, with English abstract).