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The Human Nature Review 2002 Volume 2: 122-124 ( 28 March )
URL of this document http://human-nature.com/nibbs/02/mckee.html
The Riddled Chain: Chance, Coincidence and Chaos in Human Evolution
By Jeffrey K. McKee
Rutgers University Press, New Brunswick, New Jersey, 2000.
Reviewed by C. Loring Brace *, Professor of Anthropology, University of Michigan, USA.
This is a thoughtful and thought-provoking book, but, although it is well-written, it is not an easy book to read. A stress on the coincidental, the chaotic, and the random does not contribute to a coherent narrative. Early on, the author argues for the point in his title where he declares: “The links of the human evolutionary chain were riddled with chance, coincidence and chaos” (p. 18). The narrative alternates between musings on evolutionary theory and autobiographical reminiscences. The latter are lively and interesting and keep the reader’s attention better than the ‘possibly’ and ‘on the other hand’ style of the ruminations on evolutionary dynamics.
After earning his doctorate in anthropology in America, Jeffrey McKee spent some years in the Department of Anatomy headed by the distinguished anatomist-paleoanthropologist Phillip V. Tobias at the University of the Witwatersrand in Johannesburg, South Africa. Between teaching terms, McKee ran excavations at Taung on the southeast edge of the Kalahari Desert. That was the site where the first specimen of Australopithecus africanus was discovered in 1924. Phillip Tobias’ mentor and predecessor in the Department of Anatomy, the late Raymond A. Dart, had promoted that Australopithecus fossil, which had been conveyed to him for study, as an early stage in human evolution. His gambit had been greeted with sarcastic scorn by the scientific establishment when it was first offered, but several decades later opinion began to change. Today Dart’s initial interpretation is basically accepted by virtually everyone in that most factional and idiosyncratic of fields, paleoanthropology.
McKee spent seven years supervising excavations at the Taung site, but although he recovered plenty of traces of ancient baboons, he found not one scrap of a fossilized human relative. He also supervised continuing excavations at Makapansgat some ways north of Johannesburg, the site of further discoveries of Australopithecines made over fifty years ago. Again his efforts were not successful in uncovering the remains of early human relatives. In spite of the absence of early hominids, his accounts of his experiences in his fieldwork make for the most vivid and engrossing parts of his book.
Unlike many of those now writing on human evolution, McKee makes a serious effort to deal with the events and processes that produce evolutionary change. Much of his actual investigation of these matters was accomplished by way of computer simulations. The business of introducing modifications – ‘mutations’ – into a computer-simulated population of 10,000 individuals, of tinkering with variables such as coefficients of advantage, and of letting the computer run overnight can produce useful insights, but it does not generate a gripping story line. It did lead him to reject the theme articulated by Ian Tattersall that advantageous mutations in a large population cannot be a source of evolutionary change. I had similarly rejected that same claim made by Tattersall in my assessment of his book, The Monkey in the Mirror, in Human Nature Review, but McKee’s reaction to the previous versions of Tattersall’s stance was somewhat more trenchant than mine. He has referred to Tattersall’s claim as “Balderdash” (p. 234).
McKee has also come to the defense of what I called the Probable Mutation Effect (Brace 1963). That is, where selection for a given trait is relaxed or suspended, mutations affecting its form will accumulate without opposition and most of these will produce a reduction of the trait in question. This is an applied version of the ‘neutral model’ and it provides the mechanism for Darwin’s observation that reduction inevitably follows prolonged disuse. Although McKee has accepted that generalization in principal, he has not gone on and applied it in systematic fashion to the course of hominid evolution. It has long been my claim that crucial innovations in the cultural realm reduced the intensity of selection maintaining Middle Pleistocene levels of muscularity and robustness, and that the ensuing accumulation of randomly occurring mutations were what then led to the reductions by which ‘modern’ human form was generated. A consideration of these matters is missing from The Riddled Chain.
The main gambit of the book is his offering of the concept of “autocatalysis” which is the title of chapter 8. By autocatalysis or autocatalytic evolution he refers to “intrinsically driven and self-propelled” biological change. In that chapter he poses the rhetorical question. “Can a species be its own evolutionary catalyst?” (p. 128). His answer is that “autocatalysis occurs when change in something is stimulated by one of its own products” (idem). At the same time McKee was writing this, I had restated a version of its application to the unique case of human evolution: “The Human condition is both the producer and the product of that phenomenon of its own creation, the cultural ecological niche” (Brace 2000:374). McKee does not really come to grips with the way that culture in general and specific aspects of culture in particular have directly determined the direction of human evolution. Although I did not refer to the process as autocatalysis, in essence, however, I had applied his concept even if I had not used its name. In any case, it is good to see a full statement in print of the importance of both self-imposed circumstances and the luck of the draw in influencing the course of human evolution.On the down side, McKee overextends his claims for autocatalysis and declares that it played a role in producing a cerebral expansion that was somehow induced by bipedalism. Further, he claims that facial reduction allowed frontal lobe expansion. As he put it, “A large face gets in the way of an expanding brain” (p. 207). Such assertions are simply expressions of untested faith and are closer to mysticism than science. The factors controlling brain growth, the development of bipedalism, and facial reduction are independent of each other, and the trajectory of each is unrelated to that of the others. Extensive studies have been devoted to attempts to account for each one, but none of these are given any recognition or consideration. Autocatalysis almost certainly did play a role in hominid cerebral expansion, and bipedalism contributed to the circumstances which led to that burgeoning of the brain, but the structural modifications that were involved in changing a quadruped into a biped had nothing to do with the enlargement of the brain case. McKee expresses a greater admiration for Thomas Henry Huxley than for Charles Darwin, and there is an interesting parallel between his struggles with evolutionary dynamics and the difficulties Huxley had in dealing with the insights of Darwin himself. In both cases, evolution by means of natural selection gets slightly shortchanged.
Brace, C. Loring. 1963. Structural reduction in evolution. The American Naturalist 97:39-49.
Brace, C. Loring. 2000. Evolution in an Anthropological View. AltaMira Press, Walnut Creek, California. 407 pp.
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© C. Loring Brace.
* C. Loring Brace's research addresses issues of morphological variability between human populations. His investigations focus on circumstances and dynamics involved in the development of differences in human skeletal and dental dimensions, as well as the assessment of adaptive aspects of human variation such as nose form and skin color. He has made a point contrasting the aspects of human form that are under selective force control with those that demonstrably are not, and has shown how the latter can be used to evaluate populations relationships going back into the past where there are no direct historical data. He is currently working on two major projects: 1 – The Origins of Native Americans; 2 – The Emergence of "Modern" human morphology. Dr. Brace's most recent book is Evolution in an Anthropological View, AltaMira Press, 2000.
Brace, C. L. (2002). Review of The Riddled Chain: Chance, Coincidence and Chaos in Human Evolution by Jeffrey K. McKee. Human Nature Review. 2: 122-124.