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Pre´cis of Evolution in Four Dimensions

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Pre´cis of Evolution in FourDimensionsEva JablonkaCohn Institute for the History and Philosophy of Science and Ideas, Tel AvivUniversity, Tel Aviv 69978, [email protected] J. Lamb11 Fernwood, Clarence Road, London N22 8QE, United [email protected]: In his theory of evolution, Darwin recognized that the conditions of life play a role in the generation of hereditary variations,as well as in their selection. However, as evolutionary theory was developed further, heredity became identified with genetics, andvariation was seen in terms of combinations of randomly generated gene mutations. We argue that this view is now changing,because it is clear that a notion of hereditary variation that is based solely on randomly varying genes that are unaffected bydevelopmental conditions is an inadequate basis for evolutionary theories. Such a view not only fails to provide satisfyingexplanations of many evolutionary phenomena, it also makes assumptions that are not consistent with the data that are emergingfrom disciplines ranging from molecular biology to cultural studies. These data show that the genome is far more responsive to theenvironment than previously thought, and that not all transmissible variation is underlain by genetic differences. In Evolution inFour Dimensions (2005) we identify four types of inheritance (genetic, epigenetic, behavioral, and symbol-based), each of whichcan provide variations on which natural selection will act. Some of these variations arise in response to developmental conditions, sothere are Lamarckian aspects to evolution. We argue that a better insight into evolutionary processes will result from recognizingthat transmitted variations that are not based on DNA differences have played a role. This is particularly true for understanding theevolution of human behavior, where all four dimensions of heredity have been important.Keywords: cultural evolution; Darwinism; directed mutations; epigenetic inheritance; evolutionary psychology; informationtransmission; Lamarckism; language evolution; memes; social learning1. IntroductionSince its beginning in the early 19th century, the history ofevolutionary theory has been a stormy one, marked bypassionate and often acrimonious scientific arguments. Itbegan with Lamarck, who 200 years ago presented thefirst systematic theory of evolution, but it was largelythrough the influence of Darwin’s On the Origin ofSpecies (Darwin 1859; henceforth Origin in this article)that evolution took center stage as the foremost integratingtheory in biology. In the late 19th and early 20th centuries,the theory went through neo-Darwinian, neo-Lamarckian,and saltational upheavals, but eventually it achieved a60-year period of relative stability through what is com-monly known as the Modern Synthesis. The Modern Syn-thesis, which began to take shape in the late 1930s and hasbeen updated ever since, was a theoretical framework inwhich Darwin’s idea of natural selection was fused withMendelian genetics. The stability it gave to Darwiniantheory was the result of the elasticity biologists allowedit. By giving up some initial assumptions about strict gra-dualism, by tolerating selective neutrality, by acceptingthat selection can occur at several levels of biologicalorganization, and by other adjustments, the Modern Syn-thesis was made to accommodate much of the avalanche ofmolecular and other data that appeared in the second halfof the 20th century.EVA JABLONKA is a Professor in the Cohn Institute forthe History and Philosophy of Science at Tel Aviv Uni-versity, Israel. Her doctoral studies in molecular gen-etics were carried out in the Hebrew University,Jerusalem, and she has published papers in micro-biology and cytogenetics. More recently, her work hasbeen in epigenetics, evolution, and the philosophy ofbiology, and she is the author or coauthor of manyarticles in these fields. Jablonka has written a textbookon evolutionary biology for the Open University ofIsrael and a short book on the history of heredity(both in Hebrew), and is coauthor of Epigenetic Inheri-tance and Evolution (1995) and Evolution in FourDimensions (2005) with Marion Lamb, and of AnimalTraditions (2000) with Eytan Avital.Before her retirement, MARION LAMB was a SeniorLecturer in the Biology Department of BirkbeckCollege, University of London. Her laboratory researchand publications were in radiation biology, mutagenesisand ageing. For the past 20 years she has been workingon theoretical aspects of epigenetics and evolutionarybiology. She is author of the book Biology of Ageing(1977), and coauthor (with Eva Jablonka) of EpigeneticInheritance and Evolution (1995) and Evolution inFour Dimensions (2005).BEHAVIORAL AND BRAIN SCIENCES (2007) 30, 353–392Printed in the United States of AmericaDOI: 10.1017/S0140525X07002221# 2007 Cambridge University Press 0140-525x/07 $40.00 353One thing that most mid- and late-20th century evol-utionists were unwilling to incorporate into their theorywas the possibility that the generation of new variationsmight be influenced by environmental conditions, and,hence, that not all inherited variation is “random” inorigin. During the first 50 years of the Modern Synthesis’sreign, Lamarckian processes, through which influences ondevelopment could lead to new heritable variation, wereassumed to be non-existent. When induced variationseventually began to be recognized, they were downplayed.Developmental processes in general were not a part of theModern Synthesis, and until recently developmentalbiology had little influence on evolutionary theory. Thisis now changing, and as knowledge of developmentalmechanisms and the developmental aspects of heredityare incorporated, a profound, radical, and fascinatingtransformation of evolu tionary theory is taking place.In Evolution in Four Dimensions (Jablonka & Lamb2005; henceforth mentioned as E4D in this pre´cis), wefollowed the traditional 20th-century heredity-centeredapproach to evolutionary theory and looked at how newknowledge and ideas about heredity are influencing it.We described four different types of heritable varia tion(genetic, epigenetic, behavioral, and symbolic), some ofwhich are influenced by the developmental history of theorganism and therefore give a Lamarckian flavor to evol-ution. By systematically analyzing and discussing the pro-cesses involved, we examined the role and prevalence ofinduced variations, arguing that they are important


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