<strong>The</strong> relative contributions of heredity <strong>and</strong> environment are not additive. That is, we can’t say that such-<strong>and</strong>-such a percentage of nature <strong>and</strong> such-<strong>and</strong>-such a percentage of experience make us who we are. Nor is it accurate to say that full genetic expression happens once, around conception or birth, after which we carry our genetic legacy into the world to see how far it takes us. Genes produce proteins throughout the life span, in many different environments. Or they don’t produce these proteins, depending in part on how harsh or nourishing those environments are. <strong>The</strong> emerging view is that many complex behaviors likely have some genetic loading that gives people a propensity for a particular developmental trajectory (Plomin & others, 2001). However, the actual development requires more: an environment. And that environment is complex, just like the mixture of genes we inherit (Coll, Bearer, & Lerner, 2004; Overton, 2004; Sternberg & Grigorenko, 2001). Environmental influences range from the things we lump together under “nurture” (such as parenting, family dynamics, schooling, <strong>and</strong> neighborhood quality) to biological encounters (such as viruses, birth complications, <strong>and</strong> even biological events in cells) (Greenough, 1997, 1999; Greenough & others, 2001). Imagine for a moment that there is a cluster of genes somehow associated with youth violence (this example is hypothetical because we don’t know of any such combination). <strong>The</strong> adolescent who carries this genetic mixture might experience a world of loving parents, regular nutritious meals, lots of books, <strong>and</strong> a series of masterful teachers. Or the adolescent’s world might include parental neglect, a neighborhood in which gunshots <strong>and</strong> crime are everyday occurrences, <strong>and</strong> inadequate schooling. In which of these environments are the adolescent’s genes likely to manufacture the biological underpinnings of criminality? A controversy erupted when Judith Harris (1998) published <strong>The</strong> Nurture Assumption. In this provocative book, she argued that what parents do does not make a difference in their children’s <strong>and</strong> adolescents’ behavior. Yell at them. Hug them. Read to them. Ignore them. Harris says it won’t influence how they turn out. She argues that genes <strong>and</strong> peers are far more important than parents in children’s <strong>and</strong> adolescents’ development. Genes <strong>and</strong> peers do matter, but Harris’ descriptions of peer influences do not take into account the complexity of peer contexts <strong>and</strong> developmental trajectories (Hartup, 1999). In addition, Harris is wrong in saying that parents don’t matter. For example, in the early child years parents play an important role in selecting children’s peers <strong>and</strong> indirectly influencing children’s development (Baumrind, 1999). A huge parenting literature with many research studies documents the importance of parents in children’s <strong>and</strong> adolescents’ development (Bradley & Corwyn, 2004; Collins & others, 2000, 2001; Collins & Laursen, 2004; Collins & Steinberg, 2006; Maccoby, 2002; Parke, 2004). We will discuss parents’ important roles throughout this book. 3 Review <strong>and</strong> Reflect ● LEARNING GOAL 3 Explain the contributions of evolution, heredity, <strong>and</strong> environment to adolescent development Review • What role has evolution played in adolescent development? How do the fields of evolutionary psychology <strong>and</strong> evolutionary developmental psychology describe evolution’s contribution to underst<strong>and</strong>ing adolescence? • What is the genetic process? • What is the nature of heredity-environment interaction? Reflect • Someone tells you that he or she has analyzed his or her genetic background <strong>and</strong> environmental experiences <strong>and</strong> reached the conclusion that environment definitely has had little influence on his or her intelligence. What would you say to this person about his or her ability to make this self-diagnosis? Copyright © <strong>The</strong> <strong>McGraw</strong>-<strong>Hill</strong> Companies, Inc. Permission required for reproduction or display. Evolution, Heredity, <strong>and</strong> Environment 89 Heredity Heredity Heredity–Environment Correlation View Epigenetic View Environment Environment FIGURE 3.17 Comparison of the Heredity- Environment Correlation <strong>and</strong> Epigenetic Views <strong>The</strong> interaction of heredity <strong>and</strong> environ- ment is so extensive that to ask which is more important, nature or nurture, is like asking which is more important to a rectangle, height or width. —WILLIAM GREENOUGH Contemporary Psychologist, University of Illinois www.mhhe.com/santrocka11 Genes <strong>and</strong> Parenting Heredity Resources
REACH YOUR LEARNING GOALS PUBERTY AND BIOLOGICAL FOUNDATIONS 1 PUBERTY Determinants of <strong>Puberty</strong> Sexual Maturation Psychological Dimensions 2 THE BRAIN 3 EVOLUTION, HEREDITY, AND ENVIRONMENT <strong>The</strong> Evolutionary Perspective Growth Spurt Secular Trends in <strong>Puberty</strong> Pubertal Timing <strong>and</strong> Health Care Neurons Brain Structure Experience <strong>and</strong> Plasticity <strong>The</strong> Genetic Process Heredity-Environment Interaction 90 Copyright © <strong>The</strong> <strong>McGraw</strong>-<strong>Hill</strong> Companies, Inc. Permission required for reproduction or display.
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