As mentioned previously, the Royal Society are celebrating 350 years of publication, and in recognition of this they are offering free access to a vast number of papers, both past and present – indeed the current edition of the Proceedings of the Royal Society B (Biological Sciences) treats us to a Special Issue ‘Recent advances in Chinese palaeontology,’ organized and edited by Xing Xu, Zhe-Xi Luo and Jia-Yu Rong. As well as what appears to be a whole slew of interesting articles discussing an impressive array of fossils dating all the way back to the Cambrian, the final article concerns one of our more direct ancestors, in the guise of Homo erectus.
Here’s the abstract:
A new Homo erectus endocast, Zhoukoudian (ZKD) V, is assessed by comparing it with ZKD II, ZKD III, ZKD X, ZKD XI, ZKD XII, Hexian, Trinil II, Sambungmacan (Sm) 3, Sangiran 2, Sangiran 17, KNM-ER 3733, KNM-WT 15 000, Kabwe, Liujiang and 31 modern Chinese. The endocast of ZKD V has an estimated endocranial volume of 1140 ml. As the geological age of ZKD V is younger than the other ZKD H. erectus, evolutionary changes in brain morphology are evaluated. The brain size of the ZKD specimens increases slightly over time.
Compared with the other ZKD endocasts, ZKD V shows important differences, including broader frontal and occipital lobes, some indication of fuller parietal lobes, and relatively large brain size that reflect significant trends documented in later hominin brain evolution. Bivariate and principal component analyses indicate that geographical variation does not characterize the ZKD, African and other Asian specimens. The ZKD endocasts share some common morphological and morphometric features with other H. erectus endocasts that distinguish them from Homo sapiens.
I’ll just add a few brief notes from the paper, starting with the age of the fossil ZKD V – it was originally dated to c. 230 kya, (kya = thousands of years ago) but more recent research has pushed back the date to something between 400 kya – 500 kya, “using 26Al/10Be on buried quartz sediments and lithic artefacts from layers 7–10″.
This aluminium/beryllium isotopic dating technique was in the news earlier in 2009 when it was revealed that the oldest occupants of the site may have lived as long ago as 680,000 – 780,000 years ago, some 200 ky earlier than previous dating analyses had suggested, and further that they may have been specifically adapted to a cold climate.
The component fragments of the ZKD V skull were recovered in two separate excavations, the first of which took place in 1934 and the second in 1966. Here are details of other remains that were used in comparison to ZKD V from the paper:
Weidenreich (1935, 1943) studied the craniums of ZKD II, III, X, XI, XII and the portions of ZKD V that were then available. He suggested that the fundamental morphology of the ZKD crania remained unchanged over time. When Qiu et al. (1973) were able to study the more complete ZKD V cranium, they determined that it not only has the typical ZKD morphological characters, but also that it has what they described as more progressive features. For instance, the skull of ZKD V has a high and round temporal bone, a reduced occipital torus, and a short distance between inion and the internal occipital protuberance. Other evidence for temporal variation in ZKD H. erectus derives from studies of the human teeth (Zhang 1991) and the lithic industry (Pei & Zhang 1985).
In this paper, we analyse an unpublished endocranial cast of the ZKD V specimen and compare it with other H. erectus (ZKD II, III, X, XI, XII, Hexian, Sambungmacan (Sm) 3, Trinil II, Sangiran 2, Sangiran 17, KNM-ER 3733, KNM-WT 15 000) and Homo sapiens (Kabwe from Zambia, Liujiang from China, and a comparative modern Chinese sample). Our objective is to facilitate a more comprehensive understanding of ZKD H. erectus brain morphology and to re-examine the variability of H. erectus.
There foll0ws a more detailed discussion of the gross morphology of ZKD V, compared with cranial features of the other specimens in the study, whilst the section on bivariate morphometric analysis offers more in the way of specific measurement and statistical considerations.
Finally, a word or two on the overall context of ZKD V and its correlation to other specimens for Asia and Africa:
The taxonomic affinity of the ZKD hominins has long been questioned. Previous analyses, mostly based on study of external cranial morphology, led researchers to propose that the ZKD crania possess unique morphological and morphometric features distinguishing them from other Asian as well as African hominins (Kidder 1998; Anton 2002, 2003; Kidder & Durband 2004). According to Anton (2002), regional differentiation exists between northern Asian and southeast Asian H. erectus, and the ZKD H. erectus sample exhibits less variation than the early Indonesian sample. Other researchers argue that the cranial features thought to define Asian H. erectus are also expressed on some African specimens (Rightmire 1998). Differences between the Far Eastern and African hominins are viewed as minor and not indicative of more than one species (Braüer 1994).
Detailed endocast studies comparing Asian and other H. erectus specimens are limited in number. Begun & Walker (1993) suggested that the ZKD H. erectus endocasts are overall morphologically similar to KNM-WT 15 000. In a previous study, we found that Hexian from central-eastern China is morphologically most similar to the ZKD specimens (Wu et al. 2006). Interestingly, the nine-variable and six-variable PCA results of this study show that the six ZKD endocasts do not cluster together, and do not present a different pattern from the African or the other Asian specimens. Our research on endocast size and shape provides no support for the argument that ZKD H. erectus or other Asian H. erectus specimens represent a morphologically distinct species…
…Our studies indicate that the ZKD endocasts share some morphological and morphometric features with the African and other Asian specimens that distinguish them from the modern Chinese comparative sample. We also note that the ZKD V endocast shows some progressive features compared with the other ZKD H. erectus— ‘progressive’ in the sense that ZKD V differs in ways that foreshadow the greater overall brain height and fuller lobes that generally characterize H. sapiens. This is not unexpected given its later geological age and the possibility that as much as half a million years may be represented by the ZKD sample.
In conclusion, the researchers appear convinced that African and Asian erectus specimens conform to a single African origin theory, although I suspect that others in the field will find sufficient detail in the data that suggest a far more complex aspect to this era of human evolution.
image: Reconstructed skull and endocast of ZKD V: (a(i)(ii)) superior view; (b(i)(ii)) left lateral view; (c(i)(ii)) anterior view; (d(i)(ii)) right lateral view; (e(i)(ii)) basal view; and (f(i)(ii)) posterior view. Reconstructed areas are shown in black. Scale bar, 4 cm.
Reference: A New Homo erectus (Zhoukoudian V) Brain Endocast From China, by Xiujie Wu1, Lynne A. Schepartz and Wu Liu, Published online before print April 29, 2009, doi: 10.1098/rspb.2009.0149 Proc. R. Soc. B 22 January 2010 vol. 277 no. 1679 337-344