Mankind Evolving. The Evolution of the Human Species by Theodosius Dobzhansky (review)

Abstract

BOOK REVIEWS Mankind Evolving. The Evolution of the Human Species. By Thbodosius Dobzhansky. New Haven and London: Yale University Press, 1962. Pp. xüi+38i. $7.50. This is a remarkable book. But before I get to grips with it I must make a general criticism. Professor Dobzhansky is a great geneticist and has concentrated primarily on the analysis ofthe mechanisms making evolutionary transformation possible, with special attention to the genotype and its interaction with environmental factors. He writes from the standpoint ofa geneticist, not ofan evolutionist, and in my view has misunderstood some ofthe basic ideas ofmodern evolutionary theory. Thus his book does not fulfilthe promise ofits title. It should have beencalled Prolegomena to the Study of Human Evolution. As such it is extremely valuable. But the time is ripe for an operational treatment ofevolution, aimed at exploring how the evolutionary process actually works and produces its results in practice: a treatment both synthetic and analytic, studying the interaction of genetic, developmental, and environment factors, and emphasizing the total pattern ofits trends and achievements. I had hoped that Professor Dobzhansky would have adopted this approach in history ofthe evolution ofthe human species. He could have reminded us that each step in that evolution is simultaneously an effect and a cause, and indeed could have pointed out that the whole ofevolution, including psychosocial evolution, is a directional and cybernetic process, involving constant feedback between past result and future course. I am tempted to give one or two examples. The evolution ofcolor-vision, for instance, promoted the evolution of adaptive visual anaesthetic characters both in the same and other species. As examples of the latter we have the color-patterns of insect-pollinated flowers and the warning coloration ofnauseous or dangerous animals; and ofthe former we have recognition marks and sexual display characters. In die sexual behavior ofbirds, the conflict ofsexual, aggressive, and fear drives may result in what the ethologists call displacement activities. In origin, these are purely consequential characters—adaptively irrelevant resultants ofthe evolutionary situation; but they have frequently been utilized by selection and converted into functionally valuable display characters. Mammals appear to have lost the capacity for color-vision early in their evolution. As a result, their coloration is confined to blacks, whites, greys, browns, and russets. However, color-vision was reacquired by the primates, with the result that pure blues, greens, and reds reappear in their allaesthetic color-patterns. The red is always due to blood. Originally, the red color of blood was a consequential character, a biologically irrelevant consequence ofthe chemical structure ofhemoglobin. But in various primates, including ourselves, it has acquired an allaesthetic function, which in turn has become the basis for an important sector ofthe cosmetics industry. 144 Book Reviews Perspectives in Biology and Medicine · Autumn 196z Indeed, the evolution ofman from an early primate stock provides one ofthe most startling examples ofevolutionary cybernetics. AsJ. B. S. Haldane pointed out years ago, aseries ofmutuallyreinforcingstepswerenecessaryforthisprocess. Anarboreal omnivorous life promoted the evolution ofbinocular vision, fine visual-tactile discrimination, and manipulative skill. These in turn promoted, or at least made possible, the development of practical intelligence and problem-solving ability. Arboreal life also promoted the evolution ofmonotocy—the restriction ofthe typical mammalian litter to a single infant. And this, in turn, by abolishing intra-uterine selection for rapid development, permitted aretardationofpostnataldevelopmentandtheconsequentevolutionofa lengthy learning period. Among consequential possibilities relevant to further human (cultural) evolution, one mightmentionthepotentialcapacityoíHomosapiensforhighermathematics, whichcould only berealized in conjunctionwith a suitablepsychosocialenvironment. Asaveryrecent consequentialphenotypic character recorded byJ. M. Tanner in Chapter 7 ofhis Education andPhysical Growth (London, 1961) wehave theremarkablefactthat the onset ofpuberty in all Western nations has steadily become earlier during the last 120 years by about four months every decade. This is presumably due to improvement in environmental factors, such as nutritionandpublic health; but whatever its origins, it clearlycouldhaveinteresting biological as well as social effects on further psychosocialevolution. An operational approach could also attempt to describe and understand the various subprocesses included in the over-allprocess ofevolution. There would appear to be four such subprocesses—cladogenesis, leading to diversification; anagenesis, leading to improvement and higher organization; stasigenesis, leading to stabilization and persistence oftype; anddiffusion, leading to areversalofdiversification,andtounificationofdiffèrent evolutionary lines: in biological evolution...