The key point of this article is that concepts reflecting, theories of, and methods purporting to provide support for genetic reductionism are egregiously flawed, counterfactual, and unequivocal reflections of scholarly failures. Evidence derived from evolutionary and developmental biology, as well as from my own field, the study of human development across the life span, not only destroy any remaining enthusiasm for genetic reductionism but also provide an alternative, relational developmental systems model for understanding the role of genes in human life. In addition, relational developmental systems ideas provide reason for optimism about the potential success of programs and policies aimed at enhancing the lives of diverse individuals.
There are many ways to explain the nature of the support for the key point of this article. However, I will focus on a discussion of the ways in which the contemporary study of human development provides this support.
A Brief History of Developmental Science
Across much of its history, the major disciplinary frame within which the human life span was studied was developmental psychology. This field was embedded in a Cartesian world view. As a consequence, the field held as its core conceptual issue split conceptions of the world, such as continuity versus discontinuity, stability versus instability, and of course nature versus nurture, with the latter issue cast in many ways, e.g., heredity versus environment, maturation versus learning, or nativism versus empiricism.1 The fact that these split conceptions were regarded as reflecting the fundamental conceptual issues of the field legitimated genetic reductionist ideas and rationalized as plausible theories or approaches (e.g., behavior genetics, sociobiology, or evolutionary psychology) that claimed to explain how genes provided the fundamental material bases of human behavior and development, and did so independent of fusions with the ecology or context of human development.2
However, today, developmental psychology has been transformed into developmental science. As richly illustrated by the chapters across the four volumes of the Handbook of Child Psychology, 6th edition,3 as well as in other major publications in the field,4 the study of human development has evolved from being either a biogenic or a psychogenic approach to conceptualizing and studying the life span to a multidisciplinary approach that seeks to integrate variables from biological through cultural and historical levels of organization into a synthetic, co-actional system.5 As such, reductionist accounts of development that adhere to a Cartesian dualism, and that pull apart facets of the integrated developmental system, are rejected by proponents of relational developmental systems theories6 and, as well, by evolutionary biologists who embrace integrative, biology-context ideas as pertaining to both phylogeny and ontogeny.7 For instance, while gene structure, function, and selection constitute one dimension of evolution, epigenesis, the behavioral actions of organisms, and culture represent three additional dimensions of evolution that are integrated with genes to foster evolutionary change.8
Indeed, this multidimensional and integrative view of evolution directly involves a similarly multidimensional and integrative view of ontogeny as being constituted by four integrated dimensions. That is, and reflecting a new way of conceptualizing the links between ontogeny and phylogeny,9 there is evidence that gene structure and function across ontogeny involve mutually influential relations with a culturally- and historically-textured ecology of human development. This context is both a product and a producer of the intentional self-regulations of humans (e.g., involving the cognizing of their purposes, their selection and management of goals, and their executive functioning, strategic thinking, resource recruitment, and attentional and emotional control), actions that create emergent (epigenetic) characteristics over the life span and across generations.
Genes within the Developmental System
Reflecting this four-dimensional view of ontogenetic change, Charney points to how the contemporary scientific study of genetics is signaling not only a non-split approach to developmental science but, as well, is tolling a death knell for genetic reductionist approaches such as behavioral genetics. He says that:
The science of genetics is undergoing a paradigm shift. Recent discoveries, including the activity of retrotransposons, the extent of copy number variations, somatic and chromosomal mosaicism, and the nature of the epigenome as a regulator of DNA expressivity, are challenging a series of dogmas concerning the nature of the genome and the relationship between genotype and phenotype. DNA, once held to be the unchanging template of heredity, now appears subject to a good deal of environmental change; considered to be identical in all cells and tissues of the body, there is growing evidence that somatic mosaicism is the normal human condition; and treated as the sole biological agent of heritability, we now know that the epigenome, which regulates gene expressivity, can be inherited via the germline. These developments are particularly significant for behavior genetics for at least three reasons: First, these phenomena appear to be particularly prevalent in the human brain, and likely are involved in much of human behavior; second, they have important implications for the validity of heritability and gene association studies, the methodologies that largely define the discipline of behavior genetics; and third, they appear to play a critical role in development during the perinatal period, and in enabling phenotypic plasticity in offspring in particular.10
One striking example of the transformative role of epigenetic processes in the development across the life span of phenotypic plasticity among siblings exists in regard to monozygotic (MZ) twins. Fraga, Ballestar, Paz, Ropero, Setien, et al. (2005) note that, although MZ twins share a common genotype, most MZ twins are not identical, in that many types of phenotypic differences exist (e.g., in regard to susceptibility to disease and several anthropomorphic characteristics). Fraga et al. suggest that epigenetic differences between MZs may account for these instances of divergence across development. Accordingly, Fraga and colleagues assessed global and locus-specific differences in DNA methylation and histone acetylation among a group of white MZ twins from Spain (N = 80; 62.5% female; mean age = 30.6 years, SD = 14.2 years). Fraga et al. found that "although twins are epigenetically indistinguishable during the early years of life, older monozygous twins exhibited remarkable differences in their overall content and genomic distribution of 5-methylcytosine DNA and histone acetylation, affecting the gene-expression portrait."11 Indeed, 35% of the 80 MZ pairs had significant differences in their DNA methylation and histone acetylation profiles.
Other examples that link epigenesis and human development are provided by Lickliter and Honeycutt (2010). They note that evidence from developmental biology, neuroscience, and developmental psychology contradict the ideas that "instructions for building organisms reside in their genes, that genes are the exclusive vehicles by which these instructions are transmitted from one generation to the next, and that there is no meaningful feedback from the environment to the genes."12
Together, the evidence presented by Lickliter Honeycutt (2010), and by Charney (in press) and Fraga, et al. (2005), among others13 create the basis for a true Kuhnian paradigmatic revolution.14 The findings presented by these scholars constitute anomalies (in effect, falsifications) of the "old," genetic reductionist paradigm. These anomalies result in a crisis for the reductionist paradigm and, critically, a basis for science (and for working scientists) to turn toward an available, alternative paradigm. This new paradigm is relational developmental systems theory and, consistent with Kuhn's discussion of scientific revolutions, the very findings that are anomalies in (falsifications of) genetic reductionist models (and methods) are integrated within the now dominant paradigm.15
Relational Developmental Systems Theory
Given the evidence about the role of genes in the developmental system that I have summarized, the contemporary study of human development eschews Cartesian, split conceptualizations and, in turn, favors post- postmodern, relational metatheories that stress the integration of different levels of organization as a means to understand and to study life-span human development.16 Thus, the conceptual emphasis of relational developmental systems theory, which today is at the cutting-edge of theory and research within developmental science, is placed on the nature of mutually influential relations between individuals and contexts, represented as "individual/context" relations.17 That is, in such theory, the focus is on the "rules," the processes that govern exchanges between individuals and their contexts. Brandtstädter (1998) terms these relations "developmental regulations" and notes that where developmental regulations involve mutually beneficial individual/context relations, they constitute adaptive developmental regulations.18
The possibility of adaptive developmental relations between individuals and their contexts, and the potential plasticity of human development that is a defining feature of ontogenetic change within the relational developmental system, are distinctive features of this approach to human development. As well, the core features of developmental systems models provide a rationale for making a set of methodological choices that differ in design, measurement, sampling, and data analytic techniques from selections made by researchers using split or reductionist approaches to developmental science. Moreover, the emphasis on how the individual acts on the context to contribute to the plastic relations with it fosters an interest in person-centered (as compared to variable-centered) approaches to the study of human development.19
Furthermore, the array of individual and contextual variables involved in these relations constitutes a virtually open set. Estimates are that the odds of two genetically identical genotypes arising in the human population is about one in 6.3 billion, and each of these potential human genotypes may be coupled across life with an even larger number of life course trajectories of social experiences.20 Thus, the number of human phenotypes that can exist is fundamentally equivalent to being infinite, and the diversity of development becomes a prime, substantive focus for developmental science.
This diversity may be approached with the expectation that positive changes can be promoted across all instances of variation, as a consequence of health-supportive alignments between people and settings. With this stance, diversity becomes the necessary subject of inquiry in developmental science. That is, to understand the bases of and, in turn, to promote individual/context relations that may be characterized as healthy, positive, adaptive, or resilient - which are relations reflecting the maintenance or enhancement of links that are mutually beneficial to individuals and context - scholars must ask a complex, multi-part question.21 They must ascertain: what fundamental attributes of individuals (e.g., what features of biology and physiology, cognition, motivation, emotion, ability, physiology, or temperament); among individuals of what status attributes (e.g., people at what portions of the life span, and of what sex, race, ethnic, religious, geographic location, etc. characteristics); in relation to what characteristics of the context (e.g., under what conditions of the family, the neighborhood, social policy, the economy, or history); are likely to be associated with what facets of adaptive functioning (e.g., maintenance of health and of active, positive contributions to family, community, and civil society)? These multiple, nested sets of conditions indicate that each person should be studied as a unique individual, an idea that has been coupled with relational developmental systems theory-predicated methodological innovations.22
The emergence of such methodological advances is important, given that addressing such a set of interrelated questions requires a systematic program of developmental research elucidating trajectories across life of individual/context relations within the developmental system. Moreover, the linkage between the ideas of plasticity and diversity that gave rise to this set of questions provides a basis for extending relational developmental systems thinking to form an optimistic view of the potential to apply developmental science to promote person/context exchanges that may reflect and/or promote health and positive, successful development. Accordingly, employing a relational developmental systems frame for the application of developmental science affords a basis for forging a new, strength-based vision of and vocabulary for the nature of human development and for specifying the set of individual and ecological conditions that, together, may reflect a positive, strength-based perspective about human development.23
Quite simply, genes are not the to-be-reduced-to entities that provide any "blueprint" for behavior or development, nor do they function as a "master molecule;" they are not the context-independent governors of the "lumbering robots"24 housing them; and they are not the fixed material basis of the grand synthesis of heredity and Darwinism found in the neo-Darwinian model.25 Instead, and consistent with the four-dimensional, and neo-Lamarckian system involved in evolution,26 genes are a plastic feature of the four-dimensional, epigenetic, action-oriented, and cultural and historical ontogenetic system that constitutes the fundamental process of human development across the life span.
Given the plasticity of the relational developmental system within which genes are embedded, a final split between basic and applied science may be overcome. We may be optimistic that the future of genetic research will be marked by new information about how we can promote epigenetic changes that enhance the probability of more positive development among all individuals across the life course.
Richard M. Lerner, PhD, is Bergstrom Chair in Applied Developmental Science and the Director of the Institute for Applied Research in Youth Development at Tufts University.
The writing of this article was supported in part by grants from the John Templeton Foundation, the Thrive Foundation for Youth, and the National 4-H Council. I am grateful to G. John Geldhof, Gary Greenberg, Jacqueline V. Lerner, Jarrett M. Lerner, Peter C. M. Molenaar, Megan Kiely Mueller, Willis F. Overton, and Kristina L. Schmid for their comments. Richard M. Lerner may be contacted at firstname.lastname@example.org.
1. For reviews, see:
Lerner, R. M. (2002). Concepts and theories of human development (3rd ed.). Mahwah, NJ: Lawrence Erlbaum Associates.
Overton, W. F. (2006). Developmental psychology: Philosophy, concepts, methodology. In R. M. Lerner (Ed.), Handbook of child psychology, vol. 1: Theoretical models of human development (6th ed., pp. 18-88). Editors-in-chief: W. Damon & R. M. Lerner. Hoboken, NJ: John Wiley & Sons.
Overton, W. F. (2010b). Life-span development: Concepts and issues. In W. R. Overton (Ed.), Cognition, biology, and methods across the life span: Vol. 1, Handbook of life-span development. Editor in chief: R. M. Lerner. Hoboken, NJ: Wiley.
2. For critiques, see:
Greenberg, F. (2011). The failure of biogenetic analysis in psychology: Why psychology is not a biological science. Research in Human Development, 8(3-4), 173-191.
Gottlieb, G. (1998). Normally occurring environmental and behavioral influences on gene activity: From central dogma to probabilistic epigenesis. Psychological Review, 105, 792-802.
Overton, W. F. (2011). Relational developmental systems and quantitative behavior genetics: Alternative of parallel methodologies. Research in Human Development, 8(3-4), 258-263.
3. Damon, W., & Lerner, R. M. (Eds.). (2006). Handbook of Child Psychology (6th edition). Hoboken, NJ: Wiley & Sons.
4. Bornstein, M. H., & Lamb, M. E. (Eds.). (2010). Developmental science: An advanced textbook (6th edition). New York: Taylor and Francis.
Lamb, M. E., & Freund, A. M. (Eds.) Handbook of life-span development, Volume 2: Social and emotional development (Editor-in-Chief: R. M. Lerner). Hoboken, NJ: Wiley, 2010.
Overton, W. (Vol. Ed.), (2010a). Cognition, Biology, Methods. Volume 1 of The Handbook of Life-span Development (Editor-in-Chief: R. M. Lerner). (pp. 1-29). Hoboken, NJ: Wiley.
5. Elder, G. H., Jr. (1998). The life course and human development. In R. M. Lerner (Vol. Ed.) & W. Damon (Ed.), Handbook of child psychology: Vol. 1 Theoretical models of human development (5th ed., pp. 939-991). New York: John Wiley.
Gottlieb, G. (1997). Synthesizing nature-nurture: Prenatal roots of instinctive behavior. Mahwah, NJ: Lawrence Erlbaum Associates, Inc.
Hood, K. E., Halpern, C. T., Greenberg, G., & Lerner, R. M. (Eds.). (2010). The handbook of developmental science, behavior and genetics. Malden, MA: Wiley Blackwell.
Molenaar, P. C. M. (2010). On the limits of standard quantitative genetic modeling of inter-individual variation: Extensions, ergodic conditions and a new genetic factor model of intra-individual variation. In K. E. Hood, C. T. Halpern, G. Greenberg, & R. M. Lerner (Eds.). Handbook of developmental systems, behavior and genetics. (pp. 626-648). Malden, MA: Wiley Blackwell.
6. Mistry, J., & Wu, J. (2010). Navigating cultural worlds and negotiating identities: A conceptual model. Human Development, 53, 5-25; Overton, 2010b.
7. Ho, M. W. (2010). Development and evolution revisited. In K. E. Hood, C. T. Halpern, G. Greenberg, & R. M. Lerner (Eds.). Handbook of developmental systems, behavior and genetics. (pp. 61-109). Malden, MA: Wiley Blackwell.
Ho, M. W., & Saunders, P. T. (Eds.). (1984). Beyond neo-Darwinism: Introduction to the new evolutionary paradigm. London: Academic Press.
Gissis, S. B., & Jablonka, E. (Eds.). (2011). Transformations of Lamarckism: From subtle fluids to molecular biology. Cambridge, MA: The MIT Press.
Jablonka, E., & Lamb, M. J. (2005). Evolution in four dimensions: Genetic, epigenetic, behavioral, and symbolic variation in the history of life. Cambridge, MA: MIT Press.
8. Jablonka & Lamb, 2005
9. e.g., see Gould, S. J. (1977). Ontogeny and phylogeny. Cambridge, MA: Harvard University Press.
10. Charney, E. (in press). Behavior genetics and post genomics. Behavioral and Brain Sciences.
11. Fraga, M. F., Ballestar, E., Paz, M. F., Ropero, S., Setien, F., Ballestar, M. L., Heine-Sun, D., Cigudosa, J. C., Urioste, M., Benitez, J., Boix-Chornet, M., Sanchez-Aguilera, A., Ling, C., Carlsson, E., Poulsen, P., Vaag, A., Stephan, Z., Spector, T. D. Wu, Y., Plass, C., & Esteller, M. (2005). Epigenetic differences arise during the lifetime of monozygotic twins. Proceedings of the National Academy of Sciences, USA, 102, 10604-10609; p. 10604.
12. Lickliter, R. & Honeycutt, H. (2010). Rethinking epigenesis and evolution in light of developmental science. In M.S. Blumberg, J.H. Freeman, & S.R. Robinson (Eds.), Oxford handbook of developmental behavioral neuroscience. Oxford: Oxford University Press, pp. 30-47; p. 33.
13. e.g., Ho, 2010; Ho & Saunders, 1984; Greenberg, 2011; Gisses & Jablonka, 2011; Hood, et al., 2010; Jablonka & Lamb, 2006; Molenaar, 2010
14. Kuhn, T. S. (1962). The structure of scientific revolutions. Chicago: University of Chicago Press.
15. Overton, W. F. (in press). Evolving scientific paradigms: Retrospective and prospective. In L. L’Abate (Ed.). The role of paradigms in theory construction. New York: Springer.
16. Overton, 2010b; Overton, in press; Overton, W. F., & Müller, U. (In press). Meta-theories, theories, and concepts in the study of development. In R. M. Lerner, M A. Easterbrooks, & J. Mistry (Eds.) (2011). Comprehensive Handbook of Psychology: Developmental Psychology (Volume 6). Editor-in-Chief: Irving B. Weiner. New York: Wiley.
17. e.g., see the two volumes of the Handbook of Life-Span Development; Lamb & Freund, 2010; Overton, 2010a
18. Brandtstädter, J. (1998). Action perspectives on human development. In R. M. Lerner (Ed.), Theoretical models of human development. Volume 1 of the Handbook of child psychology (5th ed., pp. 807-863), Editor-in-chief: W. Damon. New York: Wiley.
19. e.g., see Molenaar, P C. M. (2007). On the implications of the classical ergodic theorems: Analysis of developmental processes has to focus on intra-individual variation. Developmental Psychobiology, 50, 60-69.
Nesselroade, J. R., & Molenaar, P. C. M. (2010). Emphasizing intraindividual variability in the study of development over the lifespan. In W. R. Overton (Ed.), Cognition, biology, and methods across the life span: Vol. 1, Handbook of life-span development. Editor in chief: R. M. Lerner. (pp. 30-54). Hoboken, NJ: Wiley.
20. Hirsch, J. (2004). Uniqueness, diversity, similarity, repeatability, and heritability. In C. Garcia Cole, E. Bearer, & R. M. Lerner (Eds.), Nature and nurture: The complex interplay of genetic and environmental influences on human behavior and development (pp. 127–138). Mahwah, NJ: Erlbaum.
21. Lerner, R. M., Agans, J. P., Arbeit, M. R., Chase, P. A., Weiner, M. B., Schmid, K. L., & Warren, A. E. A. (In press). Resilience and positive youth development: A relational developmental systems model. In. S. Goldstein and R. Brooks (Eds.), Handbook of Resilience in Children (2nd Ed.).New York: Springer Publications.
Lerner, R. M., Schmid, K. L., Weiner, M. B., Arbeit, M. R., Chase, P. A., Agans, J. P., & Warren, A. E. A. (In press). Resilience across the lifespan. In B. Hayslip Jr. & G. C. Smith (Eds.). Emerging Perspectives on Resilience in Adulthood and Later Life. New York, NY: Springer Publications.
22. e.g., Nesselroade & Molenaar, 2010; Molenaar, 2007, 2010
23. Lerner, J. V., Bowers, E. P., Minor, K., Lewin-Bizan, S., Boyd, M. J., Mueller, M. K., Schmid, K. L., Napolitano, C. M., & Lerner, R. M. (In press). Positive youth development: Processes, philosophies, and programs. In R. M. Lerner, M. A., Easterbrooks, & J. Mistry (Eds.), Handbook of Psychology, Volume 6: Developmental Psychology (2nd edition). Editor-in-chief: I. B. Weiner. Hoboken, NJ: Wiley.
24. Dawkins, R. (1976). The selfish gene. New York: Oxford University.
25. e.g., Ho, 2010; Ho & Saunders, 1984
26. e.g., Gissis & Jablonka, 2011