Can Science Resolve the Nature / Nurture Debate? E-Book

Margaret Lock

• Herausgeber: John Wiley & Sons
• Kategorie: Bildung
• Serie: New Human Frontiers - Polity
• Sprache: Englisch

Seitenzahl: 185

Veröffentlichungsjahr: 2016

Beschreibung

Following centuries of debate about "nature and nurture" the discovery of DNA established the idea that nature (genes) determines who we are, relegating nurture (environment) to icing on the cake. Since the 1950s, the new science of epigenetics has demonstrated how cellular environments and certain experiences and behaviors influence gene expression at the molecular level, with significant implications for health and wellbeing. To the amazement of scientists, mapping the human genome indirectly supported these insights. Anthropologists Margaret Lock and Gisli Palsson outline vituperative arguments from Classical times about the relationship between nature and nurture, furthered today by epigenetic findings and the demonstration of a "reactive genome." The nature/nurture debate, they show, can never be put to rest, because these concepts are in constant flux in response to the new insights science continually offers.

Leseprobe

Table of Contents

Series page

Title page

Copyright page

Epigraph

acknowledgments

preamble: Beyond the Molecular Vision of Life

The ubiquity of hype

Bridging two cultures

one: Movable Concepts: Nature and Nurture

Nature and nurture in classical Europe

The tenacity of humoral medicine

Nature, nurture, and the generation of life

Evolutionary theory: embracing progress

From inheritance to heredity

two: Promotion and Demotion of the Gene

Mechanisms of inheritance

Biometrics and the elimination of degeneracy

From positive to negative eugenics

The gene and modern preformationism

The Code of Codes

A vision of the Grail

Genomic surprises

Dark matter

Genes as composite objects

three: Reinstating Nurture: From Opposition to Commingling

From epigenesis to epigenetics

Molecular epigenetics and the reactive genome

Miniaturization of the environment

Embedded bodies

From causality to contingency

From versus to symbiosis: the microbiome and the metagenome

four: Accruing Biosocial Momentum

The Superorganic and its critics

Opening up the black box

Local biologies

The Anthropocene: nature in retreat

Toxic invasions

Malnutrition and the epigenome

Colonization and historical trauma

Biosocial becomings and situated biologies

five: Biopolitics for the Future

Can science finally resolve the nature/nurture debate?

references

Index

End User License Agreement

List of Illustrations

Figure 1.  The original Waddington “epigenetic landscape” (Waddington 1957). (Reproduced by permission of Taylor & Francis Books UK.)

Figure 2.  Various levels of chromatin organization, from chromosome to double helixSource: Darryl Leja, NHGRI, genome.gov

Guide

Cover

Table of Contents

Start Reading

Preface

CHAPTER 1

Index

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New Human Frontiers series

Harry Collins, Are We All Scientific Experts Now?

Everett Carl Dolman, Can Science End War?

Mike Hulme, Can Science Fix Climate Change?

Margaret Lock & Gisli Palsson, Can Science Resolve the Nature/Nurture Debate?

Hugh Pennington, Have Bacteria Won?

Hilary Rose & Steven Rose, Can Neuroscience Change Our Minds?

Copyright page

Copyright © Margaret Lock and Gisli Palsson 2016

The right of Margaret Lock and Gisli Palsson to be identified as Author of this Work has been asserted in accordance with the UK Copyright, Designs and Patents Act 1988.

First published in 2016 by Polity Press

Polity Press

65 Bridge Street

Cambridge CB2 1UR, UK

Polity Press

350 Main Street

Malden, MA 02148, USA

All rights reserved. Except for the quotation of short passages for the purpose of criticism and review, no part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without the prior permission of the publisher.

ISBN-13: 978-0-7456-8996-8

ISBN-13: 978-0-7456-8997-5 (pb)

A catalogue record for this book is available from the British Library.

Library of Congress Cataloging-in-Publication Data

Names: Lock, Margaret. | Gisli Palsson, 1949-

Title: Can science resolve the nature-nurture debate? / Margaret Lock, Gisli Palsson.

Description: Cambridge, UK : Polity, 2016. | Includes bibliographical references and index.

Identifiers: LCCN 2015044017 (print) | LCCN 2015049073 (ebook) | ISBN 9780745689968 (hardback) | ISBN 9780745689975 (pbk.) | ISBN 9780745689999 (Mobi) | ISBN 9780745690001 (Epub)

Subjects: LCSH: Nature and nurture. | Human genetics. | Genetics. | Human biology.

Classification: LCC QH438.5 .L63 2016 (print) | LCC QH438.5 (ebook) | DDC 616/.042–dc23

LC record available at http://lccn.loc.gov/2015044017

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Printed and bound in United Kingdom by Clays Ltd, St Ives PLC

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Nature is perhaps the most complex word in the language.

Raymond Williams, Keywords, 1976

We must seek to understand the emergent and irreducible property arising from an inextricable interpenetration of genes and environment.

Stephen Jay Gould, An Urchin in the Storm, 1987

acknowledgments

The following people have generously taken time to share their expertise with us, which, on occasion, was urgently needed: Evelyn Fox Keller, Hannah Landecker, Richard Lock, Margaret McFall-Ngai, Jörg Niewöhner, Barbara Prainsack, and Faith Wallis. We are also indebted to two anonymous reviewers for their insightful and encouraging comments. Finally, we would like to thank everyone at Polity Press, who have been exceptionally supportive throughout the preparation of this book.

preambleBeyond the Molecular Vision of Life

Numerous people take it for granted today that genes cause certain kinds of developmental problems and diseases. Down syndrome comes to mind, as do images of Stephen Hawking wheelchair-bound with motor neuron disease. But these same people assume that, in addition to genes, lifestyle and environment are implicated to varying degrees in conditions such as heart and lung diseases, asthma, obesity, and diabetes. In other words, poor habits and toxic environments somehow interact with genes, with negative consequences. Researchers are likely to express this situation in terms of the percentage input from genes and environment respectively involved in any given condition. Conversely, “healthy” lifestyles and environments can be protective.

The burgeoning field of epigenetics challenges received wisdom about the relationship – and relative importance – of genes and environment, nature and nurture. From the early twentieth century, following recognition of the significance of Gregor Mendel's work on pea plants, an assumption gradually took hold among numerous geneticists that genes fully account for human biology and behavior. This position was consistently countered for the next few decades by researchers who argued that human behavioral traits develop almost exclusively from environmental influences, following John Locke's late seventeenth-century idea of a tabula rasa. However, the demonstration of the existence of DNA and its helical structure in the 1950s ensured that genetic determinism under the designation of “The New Synthesis” was rapidly consolidated as the dominant approach to understanding life itself.

Massive infusions of money were put into research in genetics, and critics of gene-centrism, biologists and social scientists alike, of whom there were a good number, were largely ignored. Now epigeneticists have added a strong voice to this critique, one grounded in molecular biology, and the century-long assumption, held by numerous scientists, that genes are the controlling force of life has been badly shaken by these claims to the contrary.

Epigenetics literally means “over or above genetics,” but its concise meaning changes and becomes further elaborated as new discoveries come to light. A few years ago, scientists in the expanding subfield of behavioral epigenetics claimed that they had uncovered molecular links between nature and nurture, that is, evidence that nature/nurture is not divisible. This assertion was based on research demonstrating how environmental stimuli and stressors originating externally and internally to the body initiate trains of molecular activity that modifies how DNA functions during individual development, at times with life-long effects on human behavior and wellbeing. The epigenetic mechanism best researched to date is methylation, a process initiated by enzymes in which DNA sequences are not changed, but one nucleotide, cytosine, is converted to 5-methylcytocine, resulting in changes to the shape or character of the nucleotide base, thus rendering a portion of DNA inactive. Protein methylation also takes place. Animal research has shown that methylation modifications can even be transmitted intergenerationally.

Debates about the locus of responsibility for malaise and disease, policy making relating to human wellbeing, and discussion about social justice in connection with healthcare are increasingly taking epigenetic findings into consideration, a move that will have wide-ranging social and political consequences.

The ubiquity of hype

In the first years of the twenty-first century, when mapping the human genome was close to completion, many experts and members of the public alike thought that with the “blueprint of life” in our hands, substantial improvements in health, illness, and wellbeing would soon follow. The hyperbole before and during the tedious process of mapping the genome was extraordinary. As early as 1988, the United States Office of Technology Assessment claimed that emerging genetic information would bring about a “eugenics of normalcy,” ensuring that “each individual has at least a modicum of normal genes.” It was claimed that eugenic practices carried out since the early part of the twentieth century would from now on be achieved through “technological” as opposed to “social controls,” thus achieving “a paramount right to be born with a normal, adequate, hereditary endowment” (United States Office of Technology Assessment 1988: 86).

A second report, Predictive Medicine, published in 1988 by the European Commission, claimed that individuals would be protected from the kinds of illnesses to which they are most vulnerable, and transmission of genetic susceptibilities to the next generation would be prevented. This “neo-eugenics,” as it was termed, designed to detect and abort “unsuitable” fetuses through the implementation of genetic screening programs, was fostered in the 1980s and early 1990s with the blessing of Margaret Thatcher and like-minded European politicians, specifically in order to reduce future healthcare expenditure. Extensive critical commentary by German Greens, activist Catholics, and certain conservative politicians, however, ensured that “predictive medicine” was never funded.

Following completion of the Human Genome Project, another round of promises were made, among them the development of personalized drugs, and the prevention of common diseases through the detection and modification of genes. These endeavours have had limited success, although significant advances in genotyping cancer tumors have improved treatment outcomes and a powerful new technology that enables editing of specific genes has enormous potential.

Epigenetic findings have raised the stakes enormously – some claim that a paradigm shift is taking place, and a new round of hype has appeared. On the cover of its issue for January 6, 2010, Time magazine displayed the unzipping of the DNA double helix under the title “Why your DNA isn't your destiny: The new science of epigenetics reveals how the choices you make can change your genes – and those of your kids.” The related article by John Cloud suggests that a single winter of overeating as a youngster can initiate a biological chain of events eventually contributing to the death of one's grandchildren.

The number of publications carrying “epigenetics” in their titles in 2010 amounted to a stunning 20,000. Since then, success stories have rapidly escalated. The annual number of papers with either “epigenetics” or “epigenetic” in their titles indexed by WorldCat from 2011 to 2015 is 25,208 (books, theses, journal articles, and book chapters). In comparison, annual figures prior to 1995 were in two digits or less. Googling the word “epigenetics” in late 2015 yielded 3.5 million hits, and a molecular biologist claims that this new discipline is “revolutionising biology” (Carey 2012: 6). Research is underway to develop pharmaceutical interventions to reverse epigenetic changes, although this is virtually confined thus far to the management of cancer. A significant transformation is apparently brewing in the world of molecular biology, and while some dismiss this as a transient bubble, they are doing so with less and less conviction as time passes.

Bridging two cultures

In 1959, the chemist and novelist C.P. Snow published the now classic book Two Cultures, in which he lamented that intellectual life in “western society” was divided between the sciences and the humanities – a split, he argued, that hindered efforts to solve the world's problems. Such a division is strikingly evident today within the academic field of anthropology (our own speciality): research into human “nature” – biological evolution and variation – has been divorced from research into “nurture” – the social, economic, political, and cultural contexts in which people live.

A 2012 editorial in Nature (490, 11) suggests that, in light of recent developments in epigenetics and related fields, the time is overdue for social scientists and biologists “to bury the hatchet” and abandon the long-standing “fortresses” of nature and nurture. But it is one thing to transcend the hostile intellectual domains of previous generations, and quite another to form a united effort to address the growing recognition among many researchers in the biological and social sciences respectively of the entanglement of biology in environmental, social, and political relations. To date, there are few signs of a fundamental change in orientation. On the contrary, it is evident that the molecular endpoints of epigenetic activity detected inside the body are capturing most attention in both the research world and the media, thus setting to one side the numerous factors external to the body that contribute to distress and disease throughout life.

Epigeneticists often “miniaturize” nurture in order to standardize their research practices. For example, it has been shown that exposure of a fetus in utero to maternal stress and anxiety can have post-natal effects that may last for years, possibly a lifetime. Researchers attribute this to “epigenetic dysregulation” that occurred during pregnancy. The reality of the everyday lives of so many pregnant women – such as lack of money to buy food and clothing and inadequate housing – is sidelined by the majority of investigators in their search for measurable evidence of the embodiment of trauma, stress, and noxious chemicals.

Such evidence is important, but the origins of many epigenetic marks present in individual bodies can only be comprehensively accounted for by attending to history, politics, and social relations. Human bodies are not skin-bound, and the domains of the social and biological are inseparably coalesced from the moment of conception. Attempting to depict the impact of unrelenting exposure to poverty, violence, discrimination, and racism on individuals, families, and groups of people demands more than bodily evidence to give a satisfactory account of what has taken place. A chronicle of the lives of present and previous generations as recalled by living family members is important, because epigenetic marks reveal abuse endured not solely in the present but also in the past. Whether or not epigenetic changes are transmitted intergenerationally in humans remains a matter for heated debate, but if this proves not to be the case, irrefutable evidence shows that epigenetic changes arise anew in ensuing generations if living conditions are not substantially improved.

Not only do environmental stimuli, external and internal to the body, impinge on an embryo from the moment of inception, but the embryo is always already a creature of the past – it has a history: the lasting effects of evolutionary, environmental, historical, cultural, and stochastic (unpredictable) variables, to which the DNA of previous generations have continually been exposed over eons of time. When reproduction takes place, the haploid form (half the chromosomes) of the genomes of the egg and sperm contribute their histories – their cell memories – to the conceptus. Thus, certain of the embodied effects of the lived experiences of one's parents and of earlier ancestors are transferred to ensuing generations. No systematic causal trails link nurture writ large, that is, environments past and present, with individual genotypes – such pathways are neither linear nor inevitable – but, as the biologist Steven Rose puts it, this “alternative vision of living systems …recaptures an understanding of living organisms and their trajectories through time and space as lying at the centre of biology” (1997: 7).

Along similar lines, the anthropologist Tim Ingold insists that “process” should take priority over “form” and that humans, and indeed creatures of all kinds, should be recognized “not as beings but as becomings …who continually forge their ways, and guide the ways of consociates, in the crucible of their common life. In so doing, they weave a kind of tapestry. But like life itself, the tapestry is never complete, never finished. It is always a work in progress” (Ingold 2013: 8). A commingling of nature/nurture exists from conception, to which deep history contributes. The molecular aspects of this ceaseless work in progress take two forms: first, ordered, epigenetically controlled bodily development, without which none of us would live; and, second, the action of environmental variables on the genome throughout life, affecting gene expression, with both positive and negative outcomes. Inevitably, dysregulation occurs – a sign of the wear and tear of life itself and, in later life, of aging. In situations of impoverishment, dysregulation can accumulate relentlessly from gestation on, resulting in great rents in the tapestry.

The position we take is that science cannot resolve nature/nurture debates. In effect, such debates are a red herring because nature and nurture are not readily demarcated objects of scientific inquiry. On the contrary, these concepts have been movable targets throughout history, the result of endless tussles about their relationship to one another, and the delineation of their boundaries. Throughout the twentieth century, the dominant understanding was that nature and nurture were clearly divisible entities. But insights accrued from epigenetics from the latter part of the twentieth century, rapidly accumulating each year, are bringing about an ontological shift, in which nature and nurture are understood by epigeneticists, developmental biologists, embryologists, certain philosophers of biology, and an array of social scientists as always already mingled from the moment of conception; thus, boundaries formerly assumed to be clearly demarcated are dissolved, with repercussions for medical, political, and family accounts about responsibility for ill health.

Epigenetics is a young science, and not well accepted by researchers wedded to a reductionistic way of thought. Several leading researchers in epidemiology and the biological sciences argue forcefully for recognition of unpredictable events that limit the very possibility of documenting straightforward cause-and-event pathways from environments, external and internal to the body, to detectable molecular marks of embodied stress. The unknowns are numerous, among them why epigenetic marks often reverse quite quickly, and why many people who have undergone severe trauma prove to be resilient against all odds.

Moreover, epigenetic arguments are evolving, and innovative questions and new technologies will keep the kaleidoscope turning continually, transforming discussion about the relationship of nature/nurture. No doubt, at times, laboratory-based epigeneticists will declare that they have solved the puzzle once and for all. Meanwhile, the social and political origins of ill health and traumatized lives will remain unaccounted for, no matter how scientifically accurate is the documentation of embodied epigenetic marks.

Our position is that socioeconomic and political contributions to bodily distress must be taken very seriously. If not, epigenetics may become mired in a form of neo-reductionism that, even though it facilitates drug development to reverse epigenetic marks, is not sufficient. A science of epigenetically induced pathology, resembling the dominant approach in biomedicine, will not facilitate a paradigm shift; if accounts of causality originating in the environment writ large are left unattended to, or situated entirely within families, then the political significance of epigenetic findings will be impoverished. In the latter half of this book, we suggest how such an endpoint might be avoided. These ideas will not foreclose nature/nurture debates, but may nudge them in what we regard as a positive direction.

oneMovable Concepts: Nature and Nurture

In contemporary European languages, the word “nature” is derived from a Latin translation of the Greek physis. Etymologically, the meaning stems from both natura (“the course of things”) and nascere (“to be born”). Raymond Williams, claiming that nature is “perhaps the most complex word in the language” (