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Under The Microscope

THE HUMAN CAREER - HUMAN BIOLOGICAL AND CULTURAL ORIGINS 2ND EDITION by Richard G. Klein; University of Chicago Press, 1999; 840pp; $90.00

Reviewed by Dr Phil Maxwell

Books on human evolution and prehistory tend to fall into two groups: those aimed at the popular market, with an emphasis on personalities and lavish colour photographs, and the more technical accounts with site-by-site and bone-by-bone descriptions.

This book falls firmly into the latter category -- there's not a photograph to be seen, but there are 223 clear and informative line drawings, 16 tables and a list of 2,537 references. (It is also handsomely produced and almost entirely free of typographical errors.) This is obviously not your average bedtime reading, but instead an authoritative synthesis of the paleontological and archeological evidence for primate evolution.

The first chapter gives a concise review of modern evolutionary theory, including a discussion of the phyletic gradualism and punctuated equilibrium models of speciation, and an account of cladistics, the system of biological classification that has become de rigueur in vertebrate paleontology.

Chapter 2, "The geological time frame" discusses the principles of stratigraphy, compares the various techniques used to date fossil primates, and concludes with the evidence for climatic changes during the Cenozoic (the last 65 million years) and their relevance for primate evolution. No doubt because its significance has only recently become apparent, Klein doesn't mention the Late Paleocene Thermal Maximum, a short-lived but intense global warming that took place 55.5 Ma (million years ago). This is now thought to have contributed to drastic changes in mammalian faunas at this time, including the almost complete replacement of an archaic primate group (Plesiadapiformes) by some of more modern aspect.

The following chapters (totalling some 530 pages) present a chronological account of what was known of primate history in the late 1990s, and this is the meatiest part of the book, an essential source of hard information for anyone with a serious interest in human origins.

The next chapter, "Primate evolution: Late Cretaceous to Late Miocene" gives an overview of primate classification, geographic distribution and the first 70 million years or so of their history. I suspect most readers skip quickly over accounts of early primate history and only sit up and take notice when "australopithecines" make an appearance about 4.4 Ma, but later primate history is very much contingent on what happened earlier.

One startling suggestion in this chapter is that the ancestors of lemurs reached Madagascar from Africa "on floating rafts of vegetation" about 60 Ma. In view of the antiquity of primates and the relatively primitive position of lemurs in primate phylogeny, an alternative scenario would have their ancestors reaching Madagascar without getting wet, before it fully detached from Africa.

The remaining chapters covering australopithecines, Homo habilis, Neanderthals and modern humans have an astonishing amount of information on bones, archeological sites and artifacts. This will be welcomed by anthropologists, students and those of us addicted to armchair speculation on human prehistory. There is much in paleoanthropology that is controversial, and although Klein takes a firm position on some questions (e.g. he regards Neanderthals as a distinct species rather than a subspecies of H. sapiens, and is a supporter of the "out of Africa" model of modern human origins), he carefully discusses contradictory evidence and opposing ideas.

Of course paleoanthropology doesn't stand still -- largely because it is much better-funded than most other branches of paleontology -- and since the book was written at least one new fossil hominid has been described, and it has been shown Neanderthals survived much later than previously thought, and possibly interbred with anatomically modern humans. Despite these advances (and those to come), The Human Career will not date as quickly as popular accounts of human origins and will retain its status as a leading paleoanthropological source-book long after those books have ended up on the remainder table.

Dr Phil Maxwell is a paleontologist living in Waimate.