Psychology and socialization research examine the workings of the human mind and human behavior; genetics, as a branch of biology, examines the way in which traits and predispositions are transmitted from parents to their children as a result of genetic recombination.
The relationship between psychology, in contrast, and biology and genetics, has never been easy. But what makes it so difficult? It is not simply that the past still casts a long shadow on the relationship; there are other, conflicting explanations. Both psychology and genetics claim they can explain human development and behavior; a basis common to both disciplines is their acceptance of the intergenerational transmission of knowledge and skills, attitudes and behavioral predispositions. Psychology and socialization research, however, regard such transmission primarily in terms of social learning theories, while research with a biological and social orientation addresses culture’s biological and cultural transmission. Psychologists find it difficult to accept that higher cognitive functions (for example, free will, conscience, and religious attitudes) can be subject to genetic control. Geneticists accuse psychologists of simply describing human behavior while failing to explain it. From the psychologist perspective, genetic explanations are suspected of being deterministic. Must these positions remain irreconcilable for all time?
For approximately 20 years it has been possible to observe a gradual increase in willingness in psychologists to consider biological and genetic approaches when explaining human development and behavior. Key words, such as sociobiology, neurobiological science, human behavioral genetics, evolutionary psychology, life history theory, and evolutionary socialization theory, are increasingly encountered. In the United States, especially, this willingness is seen in the context of the revival of Darwinist theories in the social sciences. Several fundamental questions in biological and evolutionary behavioral sciences have a long history.
While the term genetics (coined by William Bateson in 1906) is of much more recent origin than psychology, the debate about whether nature or culture is the stronger force has a far-longer pedigree. The Latin poet Horace (65-8 B.C.) wrote “Naturam expellas furca, tamen usque recurret” (you may drive nature out with a pitchfork, yet she’ll be constantly running back). Nature and nurture as a pair of concepts can be found in Shakespeare’s The Tempest (first performed in 1611), which also deals with the opposition of nature and culture. As Prospero remarks of Caliban: “A devil, a born devil, on whose nature / Nurture can never stick; on whom my pains, / Humanely taken, all, all lost, quite lost.” Approximately 250 years later, a fellow Englishman, Francis Galton (1822-1911), introduced the nature and nurture concepts into scientific language in his work English Men of Science. Their Nature and Nurture (1874). Galton, a cousin to Charles Darwin, believed that mental qualities and success in the sciences, the arts, and public life were far more strongly determined by hereditary factors than was generally assumed. He conducted studies of families and established the basis of twin and adoption research—its methodology and use of correlation statistics. Galton and his followers were the first behavioral geneticists (biometricians), and in relevant specialist literature today Galton is acknowledged as having been the father of human behavioral genetics long before the term even existed. This line of research is now referred to as quantitative behavioral genetics.
In The Expressions of Emotions in Man and Animals (1872) Darwin developed the theory that held that reflex actions and the ability to express emotions such as anger and embarrassment must have been learned in evolutionary prehistoric times because very young children display them. As Darwin humorously observed, sneezing and coughing were inherited reflex actions, but children had to learn to use a handkerchief when blowing their noses. Darwin’s study is a forerunner of present-day evolutionary psychology.
Although Darwin and Galton were convinced that both physical and mental traits were transmitted from generation to generation, they knew little about the function of heredity. It was not until Gregor Mendel (1822-1884) and August Weismann (18341914) each published their findings that the science of heredity took its current direction. Modern Synthesis, a movement in the 1930s and 1940s led by biologists T. Dobzhansky, J. S. Huxley, E. Mayr, and G. G. Simpson, sought to combine Darwin’s theory of evolution by natural selection with Mendel’s theory of heredity (genes as heritable elements). In so doing, Lamarck’s theory of the transmission of qualities acquired over a lifetime was finally disproved and Darwin’s theory of natural selection was provided with a firm genetic basis.
The forerunners of present-day molecular genetics also date back to more than a century. In particular, the school founded by the American zoologist and Nobel prizewinner, Thomas Hunt Morgan (18661945), initiated a line of research that was likewise linked to the term behavioral genetics. Even if Hunt was an advocate of what is now referred to as classical genetics (Mendelism), several of his followers investigated chromosomes to discover the loci of the genes responsible for the development of certain gene expressions; thus, by association, Hunt was also responsible for the development of behavior in the widest sense of the term. Consequently, in order to distinguish it from classical genetics, this is referred to as developmental genetics. For many years quantitative genetics and molecular genetics found little common ground, and they developed independently of one another; however, over the last 2 decades there has been an increasing amount of cooperation in which great hopes have been invested.
In 1883 Galton coined the term eugenics. In so doing, he combined a long-term research program to clarify genetic processes over successive generations and a program concerned with family policy, in a bid to replace weakening natural selection by artificial selection. In the years before World War I a worldwide eugenics movement was launched, and national eugenics societies were founded in many countries, including Germany, England, and the United States. The political implementation of the eugenicists’ demands subsequently led to the introduction of legislation permitting compulsory sterilization on eugenic grounds. It should, however, be noted that such compulsory measures were never seriously contemplated in Great Britain, the birthplace of eugenics.
The scientific basis of old eugenics was behavioral genetics and population genetics. In contrast to their successors today, the proponents of old eugenics, moving in the direction of genetic determinism, tended to vastly overinterpret the findings of the science of heredity, and to dramatize the rate at which hereditary predispositions with undesirable phenotypic traits—such as feeble-mindednes— spread. Mendel’s genetic laws were applied equally to physical traits and to mental strengths and weaknesses. The American anthropologist and eugenicist Charles Davenport (1866-1944) attempted to prove that nomadism was genetically determined in Mediterranean peoples, and, similarly, that thalassophilia— love of the sea—was genetically determined in American naval officers. In the 1920s, following the preparatory work undertaken by Galton and his follower Karl Pearson (1857-1936), twin research based on correlation statistics was developed, and to this day it remains the methodical core of quantitative behavioral genetics.
The abuse of biology and genetics perpetrated in the service of social Darwinism and eugenically motivated compulsory sterilization meant that after World War II environmental and learning theoreticians dominated psychology and socialization theory. Today a confused belief persists that the battle against discrimination and racialism can be justified by advancing the argument that mankind is genetically equal. Ideologically loaded, biased research has constantly provided new sustenance for this confusion, as was the case in 1994 when the psychologist Richard J. Herrnstein and the political scientist Charles Murray attempted to prove that differences in intelligence existed between different human races. For fear of being accused of racialism, many psychologists and other social scientists chose to defend politically correct environmental attitudes even when the evidence pointed in the opposite direction. However, an increasing number of scientists began to realize that a politically correct rejection of academic evidence offers no protection against racialism. Racialists could not be discouraged from being racialist simply by advancing the argument that mankind was genetically uniform, regardless of the argument’s accuracy. The renowned behavioral geneticist, Robert Plomin, has stressed that the principle of equality enshrined in the U.S. Constitution referred not to genetic uniformity but to equality before the law. In all democratic societies everyone should be treated equally—despite genetic differences. Psychologists have increasingly sought to overcome the problem presented by the traditional nature/nurture argument. Critical of the fact that, for far too long, psychology had played the claims of nurture against those of nature, they demanded the establishment of a modern synthesis of biological and socio-scientific theories, a synthesis that considered cultural, social, and biological factors equally and provided a better explanation of human development and behavior than either biological or socio-scientific theories alone could offer. Three major research areas with genetic implications are significant for psychology today: quantitative behavioral genetics, molecular genetics, and evolutionary behavioral science.
Quantitative behavioral genetics. As was true of biological sciences in general, quantitative behavioral genetics remained for many years anathema to psychology, because of its involvement with eugenics. J. L. Fuller & W. R. Thompson’s 1960 Behavior Genetics was the first publication to use the term in its title. It was followed in 1970 by the foundation of the Behavioral Genetics Association and the specialist journal Behavior Genetics; despite this, the discipline retained its outsider status in psychology. This changed in the course of the 1980s and, in particular, in the 1990s. At its centenary annual conference in 1992, the American Psychological Association recognized genetics as a research area that would be of major significance in the future of psychology.
Quantitative behavior genetics regards itself as an interdisciplinary subject-area situated between life sciences and psychology. Behavioral geneticists use statistical methods to disentangle the contribution made by genes and environments to personality differences. Personality traits are behavioral traits inasmuch as they show up in test scores. Behavioral traits measurable by specific test procedures include IQ, shyness, and religious attitudes, or the traits listed in the Five-Factor Model of Personality, also known as “the big five” (extraversion-introversion, agreeableness, conscientiousness, neuroticism-anxiety, and intellectual openness). The genetic factor is controlled using a classical research model that examines monozygotic and dizygotic twins, sibling children, and adoptive children; the environmental factor is controlled by examining twins who have grown up either apart or together. The term behavioral genetics is misleading in the sense that it can imply that, as a line of research, it is concerned primarily with the effectiveness of genetic influences; this is a misconception. To establish the contribution of genetic factors involved in shaping personality traits, a calculation of the contribution of environmental factors is an essential precondition. Heritability is the assessment of relationship between genetic variance and variance of behavior. The statistical value for heritability lies between 0.00 (where the total variance is attributable to environmental factors) and 1.00 (where the total variance is attributable to genetic influences). The more behavioral genetics learns about genetic predispositions the more it will also learn about the environments in which these predispositions acquire their phenotypic form. The findings of behavioral genetics also imply, however, that the influence of environments—the family environment, for example—is smaller than assumed by psychology and socialization theory, neither of which is informed by behavioral genetics.
The relationship between genetic predisposition and the environment is dynamic. The concept genotype x environment correlation implies that human beings undergo three developmental stages before reaching adult age: passive, reactive, and active genotypes x environment correlations. The passive stage occurs when children passively inherit family environments from their parents, environments that correlate to the children’s genetic predispositions.
Reactive genotype x environment correlations describe the elicitation of responses from other individuals, based on the individuals’ own genetically based personalities. The active stage occurs when individuals choose, change, construct, or reconstruct environments that correlate to their genetic predispositions. The interaction of genome and environment depends on an individual’s age, in the sense that the influence of genetic predisposition does not simply stabilize with increasing age but actually increases. The earlier in their lives individuals can choose and actively shape their environments, the stronger the effect of genetic predispositions will be.
Molecular genetics. In the last 2 decades quantitative behavioral genetics and molecular genetics have moved closer to one another. Currently, there are high hopes of an increase in the amount of cooperation. Behavioral genetics works solely on a statistical level with genetic predispositions for behavior while molecular genetics looks for genetic loci in the genetic material (DNA molecule); these are known as quantitative trait loci (QTLs) and are connected to behavioral traits. This development was preceded in the 1980s by the discovery made in molecular genetics of how to use DNA markers for gene mapping. Molecular geneticist Lee M. Silver has recently predicted that, as their knowledge continues to grow, molecular geneticists will one day be in a position to establish connections between genetic profiles and those mental traits that we normally refer to as one’s innate talents.
Behavioral genetics hopes that the identification of QTLs will provide direct proof of the existence of genetic predispositions for behavior. But genes are not directly involved in the regulation of behavior; rather, genes regulate the production of proteins. Between the genetic basis and behavior are morphological, neurophysiological, metabolic, and other levels of control. Bidirectional connections exist between all of these with the result that genetic activity exerts an indirect influence on behavior, and, conversely, behavior exerts an indirect influence on gene activity. This means that of all interacting levels the behavior level is furthest away from the genetic basis. Thus, the protein products of the QTLs must be investigated in order to demonstrate how the product of a QTL influences a particular measurable aspect of behavior between the various levels.
But what does molecular genetics know about behavior? In this respect molecular genetics is dependent on behavioral genetics for information about what precisely constitutes measurable behavior in order to know which QTLs and protein products it should be seeking. This may be relatively simple, as in the case of Huntington’s disease (in 1993 the causal gene was discovered on chromosome 4), for example, but it is a different matter with complex personality traits such as shyness or sociability. Thus, it is not surprising that several skeptics can be found among biologists, such as Richard C. Lewontin, for example.
Evolutionary behavioral science. Present-day evolutionary behavioral sciences are rooted in European human ethology and in American sociobiology. Edward Osborn Wilson’s 1975 study Sociobiology: The New Synthesis, a highly contentious book at the time it was first published, was significant first and foremost in that it introduced the term sociobiology; however, it contributed little to the understanding of the evolutionary biology of human beings. The final chapter in this bulky work is devoted to human beings, but is only 29 pages in length.
Evolutionary approaches have meanwhile become so numerous that one can talk in terms of the evolution of evolutionary perspectives. They all assume that species-typical behavior has been genetically acquired in an environment of evolutionary adaptedness (EEA). Seen from this perspective, personality traits have distal and ultimate causes, but they are triggered, influenced, and modified by proximal internal and external stimuli. An ever-increasing number of publications in this field may be classified according to three different approaches in evolutionary behavioral sciences: evolutionary psychology, evolutionary ecology, and evolutionary cultural anthropology. Evolutionary theory is seen as a broad integrating framework for embracing almost all subdisciplines of psychology, including behavioral genetics.
It would be almost impossible to conceive of this revolution in evolutionary behavioral sciences without William D. Hamilton’s 1964 doctoral thesis, The Genetical Evolution of Social Behavior. In this work Hamilton demonstrates that the classical concept of fitness, which ascribes genetic reproductive success to an individual, fails to provide an adequate explanation of evolution by selection. In brief, Hamilton’s inclusive fitness theory holds that an individual will also promote the reproduction of his genes by behaving altruistically toward his genetic relatives because these relatives carry copies of his own genes in varying amounts, according to the degree of relationship. Inclusive fitness has two components: the reproductive success of an individual (classic fitness), and the reproductive success of his genetic relatives ( kin selection). Before Hamilton’s work was published, altruistic behavior was considered to be an alien element in evolution theory, but he succeeded in making it functionally explicable within the framework of his inclusive fitness theory. Three pioneering works by Robert Trivers, published in the early 1970s, were also of immense significance: The Evolution of Reciprocal Altruism (1971), Parental Investment and Sexual Selection (1972), Parent-Offspring Conflict (1974). These works, and the many studies based on them, provide the basis for the late 1990s new model of psychology: Evolutionary Psychology.
Below the theoretical level of inclusive fitness theory, one research concept has emerged that, in the opinion of certain researchers, is the most dynamic among all the evolutionary approaches to human behavior: Life History Theory. This theory examines the strategies of optimal generative reproduction in the life cycle. Clearly, generative reproduction is of direct relevance only to each generation of parents, but it is also active in generations that have not yet begun to reproduce (childhood/youth), or that no longer reproduce (old age); thus, the entire life cycle is regarded in terms of reproductive strategy. This means that each individual must perform a series of developmental and judgment tasks specific to his or her relevant age and dependent on his/her environment. In so doing, the individual must choose between different functional equivalences of inclusive fitness— such as age, survival resources, growth, development, information, and generative reproduction—because these equivalences are mostly limited and must be employed differently in different environments: survival versus growth, development versus reproduction, growth versus reproduction. In evolutionary life history theory, the judgment problem that dominates all others is the problem connected with current and future reproduction. With regard to parents, this implies mating, parenting, and parental investment. Mating denotes the act of reproduction (i.e., progeny in the quantitative sense); parenting and parental investment denote future reproduction (i.e., progeny in the qualitative sense). The surprising assumption is that within the specific conditions of scarce resources and insecurity about the future it can be functional for inclusive fitness for an individual to generate a larger number of offspring whereas conditions of plentiful resources and security about the future can lead to the generation of fewer offspring. In the first case, the emphasis of reproduction strategy falls on mating in an attempt to increase the likelihood that some offspring will survive and to reduce the danger of elimination from the gene pool; in the second case, both parenting and parental investment will increase the reproductive value of a smaller number of offspring (health, longer period of development, mating prospects) and, thus, the inclusive fitness of future generations will be enhanced.
A traditional problem of personality psychology is currently being addressed anew, from the perspective of evolution: What makes one human being like other human beings, and what makes him or her unique? Psychology experiences difficulties in establishing a clear theoretical position between universal statements about man in general and statements about individuals. Until now the answer to the problem has been that human nature is equipped with uniform psychological mechanisms, which, as a result of distinct individual experiences, lead to individual differences. However, this answer fails to consider the problem of individuals’ genetic differences, differences that challenge the concept of a universal human nature. The tension between individual uniqueness and the concept of a universal human nature has a parallel in evolutionary biology. Here theories about species-typical behavioral adaptations conflict with the discovery of major genetic variability (i.e., every individual has a unique combination of alleles [different forms of genes]). Evolutionary psychologists attempt to solve the problem by applying evolutionary logic to both the psychological universals that constitute human nature and the genetic differences that contribute to individual variation. Evolutionary psychologists John Tooby and Leda Cosmides believe that every personality phenomenon can be analyzed either as an adaptation, an incident byproduct of an adaptation, or the product of noise in the system, or as some combination of these three.
The problem of psychological universals versus genetic difference concerns the relationship between evolutionary psychology and quantitative behavioral genetics because behavioral geneticists are interested primarily in individual differences and less in human universality. It remains to be seen whether these two lines of research can complement and enrich one another for, despite the obvious thematic proximity of the two, they have long since been regarded as independent disciplines, each concerned with different problems and methods. While it has long been claimed that each can benefit from the other and that in matters of central concern to both they are interdependent, only in the last few years has a rapprochement of the two been evident. In the view of the American psychologist Sandra Scarr, psychology will be truly evolutionary when the discipline includes behavioral genetics.
Behavioral genetics and evolutionary behavioral sciences share the belief that behavior and its development cannot be explained solely by reference to conditions here and now. Behavior geneticist Thomas Bouchard (Minnesota Twin Project) remarked that genes sing a prehistoric song. But what song do genes sing? The general direction of cross-fertilization between these two fields is this: evolutionary theories offer a broader framework within which the results of behavioral genetics may be interpreted while development genetics provides first and foremost the methods required to test hypotheses produced in the context of evolutionary theory.
The first revolution in life sciences, Darwinism, led ultimately to eugenics, a program for the genetic advancement of mankind. Many leading biologists in the 20th century, including Thomas Hunt Morgan and Ernst Mayr rejected eugenics whereas other leading biologists, like Hermann Joseph Muller and Joshua Lederberg, welcomed it. The early promise of the program pursued by old eugenics ended in contempt for human rights and in countless acts of compulsory sterilization.
In the course of the revolution in gene technology and medical fertility treatment, new eugenics has been a topic for debate since the 1980s. Initially, critics of gene technology and reproduction medicine primarily spoke in terms of new eugenics. Conspiracy theories abounded. Businesses, insurance companies, and those responsible for health care policy are undeniably interested in genetic services. But it is unreasonable to place all science under suspicion, as if the driving force behind scientific interest was the intention to apply it in the service of eugenics. There is another alarming and perplexing development: unintentionally, even unwittingly, various branches of research in life sciences and reproduction medicine are now providing the scientific and technical potential to “rectify” the biological constitution of human beings.
In view of the steady growth of technical possibilities and of the resulting options for genetic screening programs (backdoor-eugenics) the debate conducted in the 1990s became more sophisticated, raising the question of the ethical position of so-called liberal eugenics. Liberal eugenicists maintain it is no longer enough to simply issue warnings about the dangers of playing God. They recognize the need for ethical regulation in order to avoid having to undertake a future battle about the equitable distribution of genes. Buchanan and others have written a detailed work entitled From Chance to Choice with the significant subtitle Genetics and Justice in which they ask several highly pertinent questions: Do we have the ethical resources to use our genetic powers wisely and humanly? Or are we like hapless space travelers embarking on an interstellar voyage equipped only with a pocket compass?
A central argument proposed by liberal eugenicists is that they derive the ethical basis for the genetic advancements of human nature from the individual’s right to reproductive freedom. A further central argument classifies genetic investment in children as being on the same ethical plane as educational investment. If one believes it to be self-evident that wealthy parents in democratic societies can buy environmental advantages for their children, how can one justify preventing parents from buying genetic advantages, given that both serve the same aim (i.e., to improve the child’s chances of a good life)?
Amazingly, in all the discussions of new and liberal eugenics the questions on which everything else depends is rarely articulated: What exactly is improvement of human nature? What should improved human beings look like, and how should they behave? Perhaps the simplest answer is that it is still too early to discuss the questions in detail. But when the time arrives, psychology will certainly be called upon to make its contribution even if, at this stage, it does not or will not recognize the fact. Psychology, given its access to the theory of evolution, biology, and genetics, is already playing the role of a participant who is not taking part. If scientific advance is not simply looking toward conducting genetic surgery (as in the case of Huntington’s disease and other genetically caused diseases), but is really moving toward “improving” human behavior— engineering the human germ line—it will prove difficult for psychology, as an expert in behavior, to remain aloof.
Psychology and genetics have developed separately from one another for decades. During almost all of that period of time, quantitative behavioral genetics, which could have provided an integrating link, has had a divisive effect; the last 20 years can, however, be seen as a period in which perspectives have grown closer. Quantitative behavioral genetics, molecular genetics, and evolutionary theory, are all steering a course that will ultimately lead to convergence and cooperation. A new conceptual framework, evolutionary psychology, has been established. It would be wrong to assume that this is merely a passing fashion. There will, of course, be periods of stagnation, and, while the environmentalists’ ramparts may have been weakened, they have not yet been stormed. In the short term, those who would like to see the various research areas in psychology united beneath the umbrella of the theory of evolution may be disappointed. But, as is all too evident, the ideological zeal that once established the traditional divisions— between nature and nurture, mind and body, natural sciences and the humanities—is no longer the force it once was. Beyond these divisions are very promising discoveries to be made. Many regard human identity as being lost in the process. But who would dare to argue that this identity is better preserved by maintaining these divisions? Identity does not exist once and for all time; rather, we must constantly strive to acquire a new understanding of it, time and again. The history of mankind is the history of striving to acquire an understanding of human identity repeatedly. It is vital that all men and women on Earth should share in this identity, and that genetics should not be misused in order to create new inequalities.
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