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III. Behavior Genetics: Selection's Arrow Reverses
James Brody · 12/25/02 at 2:43 PM ET
Behavior Genetics: We Unfold, We Build, We Rebel and Selection's Arrow Sometimes Reverses These are the introductory blocks. I still owe all of you segments on gene-environment interactions and on behavior genetics controversies. ------------------ "Manipulation of the environment is the ultimate adaptation." (Ed Wilson, 2000, p. 59). "All things living are in search of a better world...It may be supposed that, under the influence of Darwin's natural selection, it is the most active problem solvers, the seekers and the finders, the discoverers of new worlds and new forms of life, that undergo the fastest Evolution." Karl Popper (1984/1992, p. vii). -------------------- The tension between externalist accounts for human development, called the Standard Social Science Model (SSSM) by Cosmides and Tooby (1992), and internalist accounts such as those arising from behavior genetics and evolutionary-developmental biology (evo-devo) have never been greater. Pinker (2002) gives his reasons for the continuing debate. His latter chapters on child rearing and on politics are particularly salient here. Oddly, Steve appears to attribute social science resilience to tradition rather than to our genes. I need to read his book a third time in order to be sure of my interpretation. The conflict, however, will eventually be resolved less by reason, debate, or conversions and more according to recruitment of new generations of students and to Planck's dictum: things change in science as one generation of scientists die off and a differently behaving one takes their place.(2)(3) After all, bishops and cardinals did not resign en masse, books were not burned, and no libraries closed, took down portraits, or rededicated buildings when biology demonstrated the existence of germs and infant mortality was traced not to the sins of the mother but to the dirty hands of attendants who worked both in obstetrics and in the morgue. Behavior genetics has immense appeal: 1) We have always followed our tools and modify our beliefs in accord with what we can do with our tools (Kuhn, 1992). Behavior genetics promises a large Santa-bag of tools. 2) We have always noticed that children resemble parents. BG gives us a foundation for that belief. 3) BG puts a different responsibility on parents as a link between the child and its past. Parents are exploratory systems that sculpt a smoother fit between their child and its opportunities. Grandparents, and uncles can help as they relay gossip about the glories and scandals of prior family members. The information is not a hard prediction but sometimes a warning and a promise: lapse in one way and certain consequences will probably follow, but find an environment wherein your same traits are an advantage and expect honor and wealth rather than shame and prison to follow. Credo 1) Behavior genetics acknowledges and studies environment but often looks to internalist causes for trait development. Although you can still assume that environments crafted genes, this assumption is a half-truth and, further, it is usually impossible to verify such relationships from the imprints that we find in slate. Behavior genetics reminds us that a trait must already exist to some degree within a population and selection amplifies its expression across generations. There is, certainly, evidence that increased environmental stress in the form of heat, drought, cold, or radiation can influence the role of heat-shock proteins (Hsp 90s). These influences, however, are generally that of disinhibition: stress shows us inheritable outcomes that were already hidden within the organism. 2) Discovering order in observed variation is of great interest (Bailey, 1998; Pinker, 2002) 3) Heritability: how much of observed variation in traits is attributable to genes? And how much to environment? 4) Genes make proteins but genes also influence behavior. A "gene for shoe-tying" is an acceptable concept (John Maynard Smith, in Bailey, 1998) and language use that is consistent with the rest of science. The only debate, and it is considerable, is about the length of the causal chain and the complex alternative courses that might be set by one or a few genes that usually underlie shoe-tying. 5) Individuals define environments out of settings. Environments consist of shared (SE) and nonshared (NSE). NSE enduring, leads to differences even between MZT. SE transient and leads to similarities. SE often contributes 2% or less of variance in long term outcomes. SE seems to have greatest impact in the first several years of a child's development and fades as he samples alternative behaviors that he finds in television, movies, and friends. 6) Fitness is reflected by the range of environments that an individual can select, modify, or build. 7) Sandra Scarr (1992), "good enough" environments are sufficient for normal genetic expression. Notes and References Bailey, J. M. (1998) Can behavior genetics contribute to evolutionary behavioral science? In Crawford, C. & Krebs D (Eds) Handbook of Evolutionary Psychology. Mahwah, NJ: Erlbaum, pp. 211-234. -------------- Copyright, James Brody, 2002, all rights reserved.
James Brody
Revised for BoL posting, 12/25/02
JB
"My handwriting same as Grandfather" Charles Darwin (1)
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1) Quoted in Weiner (1999) Time, Love, Memory. NY: Knopf. Attrib. to Darwin's M notebook, 1838.
2) This is a paraphrase. Lynn Margulis has a similar one that does not acknowledge Planck. See her chapter in Margulis, L. (1995) Gaia is a tough bitch. In Brockman, J. (Ed). The Third Culture: Beyond the Scientific Revolution. New York: Simon & Schuster, 130-140.
3) A third tactical option for the shrinking left is to defend ever more vigorously their environmental positions but to do so by incorporating territory already granted to them by the behavior geneticists. That is, environment is certainly important to the point of necessity but it works in a more detailed manner, one that varies more with each individual, and one that is most often incorporated into the individual by his or her own selection of that bit of environment.
Cosmides L. & Tooby, J. (1992) The psychological foundations of culture. In J. Barkow, L. Cosmides, & J. Tooby (Eds.) The Adapted Mind: Evolutionary Psychology and the Generation of Culture. NY: Oxford.
Kuhn, T. (1992) The Structure of Scientific Revolutions (3rd Ed), Chicago: Univ. of Chicago Press.
Pinker, S. (2002) The Blank Slate: The Modern Denial of Human Nature. NY: Viking.
Popper, K. (1984/1992) In Search of a Better World. NY: Routledge.
Scarr, S. (1992) Developmental theories for the 1990s: Development and individual differences. Child Development. 63, 1-19. Scarr, S. and McCartney, K. (1983) How people make their own environments: A theory of genotype-->environment effects. Child Development. 54, 424-435. 1995: Sandra Scarr chosen as President-Elect of A.P.A. and as CEO for Kindercare.
Wilson, E. O. (1975/2000) Sociobiology: The New Synthesis. Cambridge, MA: Belknap, Harvard University Press.
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