Athena Review, Vol.4 no.1: Homo erectis: Review of Dragon Bone Hill

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Athena Review, Vol.4, no.1

Dragon Bone Hill: An Ice-Age Saga of Homo erectus

By Noel T. Boaz and Russell L. Ciochon

2004. Oxford University Press, New York. ISBN 0-19-515291-3.

Reviewed by Dong Wei, Institute of Vertebrate Paleontology and Paleoanthropology (IVPP), Chinese Academy of Sciences, Beijing

The Legend of Peking Woman and the Peking Man Site: Physical Evolution, Cultural Aspects, and Clinal Replacement

About 75 years have passed since the discovery of the first skull cap of Homo erectus pekinensis in 1929 at a site called Dragon Bone Hill, about 50 km southwest of downtown Beijing. The fossil (fig.1) has been popularly referred to as Peking Man, but anatomical study has revealed, rather, that it should have been called Peking Woman. The stories of the discovery of Peking Woman (or conventionally Peking Man), the history of excavations at the Peking Man site (fig.3), and the mysterious loss of the Peking Man fossils have been told by contemporaries, especially Professor Lanpo Jia (1908-2001), to whom Dragon Bone Hill is dedicated. While Jia’s books focused mainly on providing the detailed chronological facts of the 1920s and 1930s with literal narration and photographic illustration, Dragon Bone Hill concentrates largely on theories such as the recently developed interpretations of the Peking Man site, comparison of the locality with the other relevant sites, comments on different hypotheses of hominid evolution, and, perhaps most significantly, proposition of a new evolutionary model.

[Fig.1: Homo erectus skull from Dragon Bone Hill (photo: IVPP).]

The book is organized into nine chapters. The first two chapters of the book retrospect the history of the discovery of Peking Man and the excavations at the site, as well as the loss of the Peking Man fossils, which represent around 50 individuals. The disappearance of the Peking Man fossils during World War II remains a mystery, and fruitless attempts to recover them have been made from time to time since their disappearance. This was a great loss for world paleoanthropology, but fortunately the fossils had been cast, photographed, studied, and documented before they were lost. The casts of the fossils and publication of the initial researches were distributed worldwide, making it possible for paleoanthropologists to continue their study of the fossils. This is reminiscent of another excellent example of separate locational conservation. Several David’s deer (Elaphurus davidianus), an endemic species of China, were presented to some British explorers as gifts by the Qing Dynasty’s imperial game officers toward the end of the dynasty. The animals were shipped to England and raised there. During several Chinese civil wars as well as World War II, many wild animals were energetically hunted as food resources, and David’s deer went extinct in their homeland. The David’s deer shipped to England escaped the disaster and survived. Some of them were sent back to China by the British government in the 1980s, restoring the otherwise extinct species in China. From this and the Peking Man examples, the recommendation that invaluable fossils be at least cast and photographed, with the records conserved in separate locations as multiple backups, seems a necessity. Then, in case of destruction by disasters, such as earthquakes, meteor bombing, fire, wars, terrorist attacks, etc., essential data will be available for our continued study. Modern technologies, such as CT scanning, provide tools for further detailing and recording the data from fossils.

The third and fourth chapters discuss the physical evolution of Peking Man (fig.2). The main competing hypotheses on the subject are enumerated, and some new interpretations on Peking Man’s strangely thick skull structure are proposed. The skull of Peking Man resembles the carapace of a turtle, low and crouching, so massive and rimmed with such thick bone that his brain size was limited to barely over a quart. His mandible, or lower jaw, is also massive compared with that of modern humans, and in lateral view the skull shows only a very small chin. The authors attribute the evolving hominid skull form to three major functional imperatives: housing a brain rapidly increasing in size, serving as the bony anchor for the teeth and the muscles which move them, and, in the case of Homo erectus, defense against blunt trauma. The thickened mandible of Peking Man is also an adaptation to protect against trauma to the jaw and lower face region. All three functions are considered important by the authors in the attempt to understand the unusual cranium of Homo erectus. In addition, they suggest that the radiator brain hypothesis, in which blood circulation throughout the head and skull is thought to act as a cooling mechanism, may explain why skull thickness in Homo erectus decreased as this species evolved. According to Boaz and Ciochon, as hominid brain size increased, selection may have favored a thinner skull, which would have allowed more veins to pass through it and thus more efficient regulation of the accompanying temperature rise.

[Fig.2: Bust reconstruction of Peking Man (photo: IVPP).]

The fifth, sixth, and seventh chapters explore the cultural aspects of Peking Man, i.e. artifactual evidence for tool manufacture and use, proof for the use of fire in sedimentary deposits, speaking ability as determined by skull anatomy, as well as lifestyle. Peking Man used small quartz flakes to slice and scrape muscle from bone and hefty chopping tools made of sandstone for bigger jobs, such as cutting through the rib cage of a large carcass. Based on multiple lines of evidence, the authors interpret the Homo erectus population at the Peking Man site to have been scavengers, sometimes practicing cannibalism, rather than hunters as in many previous interpretations. The hominids developed a dependent scavenging relationship with dangerous large carnivores. Both the physical evolution and cultural aspects of Peking Man were associated with the Ice Age environment. His body size increased, and the length of his legs grew. Techniques of tool making improved as a consequence of Homo erectus’ migrations across the Old World, climatic changes accompanying the onset of the Ice Ages, and competition with carnivores for food resources and habitats. Fire was first and foremost a means by which Homo erectus could effectively compete with these other species and hold its own in the Pleistocene, especially during colder periods.

The last two chapters comment on the Out of Africa and Multi-regional Evolution hypotheses and propose a new evolutionary model, Clinal Replacement, to interpret the origin and evolution of Homo erectus. The authors support this theory with anatomical, archaeological, geological, paleontological, and paleoecological evidence. Just as in Stephen Hawkings’ efforts to unify the disparate theories of General Relativity and Quantum Physics, the Clinal Replacement hypothesis is a laudable attempt to compromise the Out of Africa with the Multi-regional Evolution hypotheses. A “cline” is defined by the authors as a geographic cluster of biological characteristics in a human population group, usually with a gradient of change in those characteristics into surrounding groups. According to the Clinal Replacement theory, Homo erectus ergaster evolved into Homo erectus erectus in both Asia and Africa at the same time. Geographically linked or bordering populations of Homo erectus had some genetic overlaps at their edges forming a kind of genetic chain. However, data from the rapidly evolving biomolecules of modern human populations do not record this relatively ancient event, since the rapid mode of molecular evolutionary change in Homo sapiens has served to overprint prior genetic change. The authors posit that this overprinting has conspired with a more complete fossil record for later phases of human evolution to give the impression of total replacement of species as hypothesized by Out of Africa theorists. In addition, total replacement does not satisfy the expectations of population genetics, nor can it resolve the disparity between the global population of hominids, which had to be large, and effective population size, which the Out of Africa model requires to be small. The Clinal Replacement theory resolves this problem by envisioning many small populations moving and replacing other populations, while explaining the continuity in traits long cited by multi-regionalists.

[Fig.3: Main fossil-producing layers at Dragon Bone Hill’s Locality 1, viewed from Pigeon Hall Cave (photo: R.L. Ciochon)]

Narrative and informative, with intermittent commentary, the style of this book may be more enjoyable for Western readers than Lanpo Jia’s book, The Story of Peking Man: From Archaeology to Mystery (Oxford University Press, 1990). In Dragon Bone Hill, Boaz and Ciochon introduce the profound theories of paleoanthropology in a simple way that makes the book reader-friendly for both experts and the general public.

Appearing in Athena Review, Vol.4, no.1 (2004), pp. 95-96.

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