All,
A paper whose abstract –- this is all I can have access to – seems to imply a chronological revision of the Zhoukoudian sequence and, therefore of Chinese "deep time" prehistory. Anyone knows about that?
Jacques Cinq-MarsFor those of you who have access to the online edition of JAS, the paper can be read by
CLICKING HERE.Sorry about not commenting as promised last Sunday, but I've been busy this week with my recovery and escape from my temporary nursing home. I have had time to review all Zhoukoudian related papers in my files, and it turns out that I have two which are directly related to the 'chronological revision' Jacques refers to above. These being:
Shen, Guan-jun & Wang, Jia-qi (2000). Chronological studies on Chinese Middle-Late Pleistocene hominid sites, actualities and prospects. Acta Anthropologica Sinica. Supplement to issue 19: 279-284.
Shen, Guanjun (2001). Current status and prospects for dating fossil hominid sites in China. IN: Tobias, P.V., Rath, M.A., Moggi-Cecchi, J. & Doyle, G.A. (eds.) Humanity from African Naissance to Coming Millennia: Colloquia in Human Biology and Palaeoanthropology. Firenze: University of Firenze Press (Florence: University of Florence Press). pp. 257-260.
It seems that Guanjun Shen and colleagues are the leading advocates for accepting U-series dating of speleothem calcites (especially employing TIMS and the latest mass spectrometry techniques) as the most reliable chronometer available for dating Chinese hominid sites, the chronology of which which in times past has been based primarily on U-series dating of fossil materials. According to Shen (2001:257), "[A]mong... 19 age sets, 8 display significant discrepancy between the results of two U-series methods", and they conclude that "on the whole we agree with other researchers working in the field that the U-series dating of fossil materials is of limited reliability' (Shen 2001:257-8).
In Shen & Wang (2000), the authors specifically describe (p. 281) "New evidence for the chronology of Peking Man", citing older studies proposing a sequence for Zhoukoudian Locality 1 of, quoting: "~700 ka for the lowest fossiliferous horizon (Layer 13), based mainly on paleomagnetic stratigraphy; ~500 ka for the lowest stone artifact-containing layer (Layer 10), based on fission track dating of sphene grains extracted from ash deposits; and ~230 ka for the uppermost strata (Layers 1-3), based on 230Th/234U dating of fossil materials."
Continuing quotation.....
"However, on close examination of the assumptions introduced by the dating methods, one finds that the validity of these dates has remained questionable. This is especially the case for the closed-system prerequisite for u-series dating of fossil materials, which provided the ~230 ka age to the upper strata" (Shen & Wang 2000:281).
"The preserved cross-section of Layers 1-2 at Locus H contain six speleothem horizons intercalatedwith detrital sediments. Using conventional [alpha] spectrometry, Shen and Jin [1991] have demonstrated that the lower part of the second flowstone layer (samples BZC89-2, 3) is of an age of 421 +110,-50 ka [1 sigma], much older than the previously assigned age of ~230 ka. Limited by the counting statistics realizable with an [alpha] spectrometer, the error range of the result is quite important. This circumstance warranted the application of the TIMS technique, which gave a much more precise age of 414 +/- 13 ka [2 sigma] for BZC89-3, in support of the [alpha] spectrometry date [Shen & Jin 1991; Shen, Ku, Gahleb, et al. 1996]. The No. V Skull of Peking Man, which is from the underlying Layer 3 and generally regarded as the youngest representative of H. erectus in China, should be therefore at least 400 ka old" (Shen & Wang 2000:281).
"Since then repeated and systematic searching along the Locality 1 cross-sections has led to the discovery of additional speleothem samples. Their TIMS 230Th/234U ages provide new evidence for the further refinement of the temporal framework of the Peking Man site [Shen, Ku, Cheng, et al., in preparation]" (Shen & Wang 2000:281).
"At Locus H, the topmost horizon produced a relatively young age of 144 +/- 1 ka. Stratigraphically downward, after ~50 cm of detrital deposition the second flowstone layer consists of two sub-units separated by a depositional hiatus. The upper sub-layer is of an age of ~300 ka. The well-studied sample of BCZ89-3, comes from the lower sub-layer, its age of ~400 ka has been re-confirmed" (Shen & Wang 2000:282).
"At the East Hillside, the flowstone representing the upper part of Layer 5 is composed of six sub-layers with a total accumulation of up to ~120 cm. Nine age measurements on four samples indicate that the lower part of this flowstone layer has a minimum age of 600 ka. As a great many hominid remains were unearthed from Layers 8-9, the widely accepted age of 450 or 500 ka for Peking Man should therefore be substantially revised. If the sedimentation rate above and below Layer 5 is assumed to be similar, then Peking Man could reach an age of 800 ka or even older" (Shen & Wang 2000:282).
The abstract from the Shen & Wang (2000) article sums it all up:
"In the past two decades new advances have been made in almost all the fields of Quaternary geochronology. The technological innovations have led to substantial changes in the timescale of the origin and evolution of human species. A general tendency is that important events in human evolution have been pushed to earlier times. This trend is having repercussions in China. The previous chronological framework for Chinese hominid sites may have been compressed. High-precision thermal ionization mass spectrometry (TIMS) U-series dates on speleothem formations show that Peking Man should be much older than previously accepted. Future developments in establishing a reliable time sequence for Chinese Mid-Late Pleistocene sites have been discussed."
Hope this helps clear some of the confusion I caused.
Cheers,
Dar
