In addition to its specific claims regarding the dynamic nature of genetic determination of behavior, Charney's target article has done a great service in drawing our attention to the underlying principles and the history of the entire idea of the complexity of genetic determination. Charney, along with others (like Johnson et al. Reference Johnson, Penke and Spinath2011), rightly claims that the genetic determination of (among other things) behavior is complex at least in two regards. First, besides genes, gene expression is crucial. His second claim, that psychometric heritability is not the only issue of genetic determinism, should be seen in the context of the recent past. The historical reminder here goes back to the 1960s. That was the time when genetic determination reappeared in psychology, but in two rival and different forms. One was the innatism proposed by Chomsky (Reference Chomsky1959; Reference Chomsky1965; Reference Chomsky1968), mainly on analogy with ethology, suggesting that complex human behaviors may be under genetic control. Innatism was one way to overcome the “empty organism” metaphor of the behaviorists.
This kind of revival of genetic determinism was entirely uninterested in individual differences, as, for example, Chomsky's (Reference Chomsky1972a) intervention in the early intelligence debates showed. Innate organizing principles of language and other complex human achievements belong to “species-specific behaviors.” For Chomsky and his followers, this kind of genetic determination is by far not determinism in the traditional sense. Genetically determined language is not a constraint on thought; rather, by its structure it is unbound and unlimited, and therefore it also ensures the unlimited free development of humanity (Chomsky Reference Chomsky1972b; Reference Chomsky1988).
At roughly the same time, the issue of genetic determinism of human behavioral and intellectual individual differences became the focus of increasing scientific attention again. This opposing view focused on things differentiating individuals. They denied that the behaviorists' life history empiricism could be a possible way to explain individual differences. To explain individual differences, they referred to the Galtonian paradigm that proposed heredity to be crucial in determining individual differences in behavior and basically presupposed an additive role of nature (genetic) and nurture (environment). The followers of Galton considered interaction as a mere statistical term (for critical surveys, see McLafferty Reference McLafferty2006; Richardson & Spears Reference Richardson and Spears1972; Taylor Reference Taylor1980).
There is a third aspect of Galton's theory, namely, that it assumes one single feature of excellence. As we emphasized a decade ago:
In psychology Darwin's theory has taken two competing forms for more than a hundred years. The first is a conservative, deterministic approach based upon the theory of natural selection and the survival of the fittest. It stresses the need to reduce the dimensions of psychological variability by finding a small number of traits in which individuals differ from each other. If someone excels in these traits, he is considered to be fitter than others. The second approach is more tolerant, emphasizes development, and considers variability itself as an evolutionary asset. (Kovács & Pléh Reference Kovács and Pléh2000, p. 1)
The hot debate regarding the validity of the Galtonian paradigm started half a century ago by Jensen (Reference Jensen1969) claiming the genetic intellectual inferiority of African Americans. Interestingly, in addition to the social value issues, the debate concerned the statistical solidity of arguing on the basis of twin research towards the hereditary nature of individual and group differences. Way before postgenomics, the issues raised were similar to those regarding the relationships between postgenomics and heritability by Charney and by Johnson et al. (Reference Johnson, Penke and Spinath2011). Kagan (Reference Kagan1969) suggested that twin research does not allow us to make intergroup comparisons, and curiously enough, his examples, as well as those in the books edited by Richardson and Spears (Reference Richardson and Spears1972) and Block and Dworkin (Reference Block and Dworkin1976), consider the highly heritable trait of height as also being influenced and controlled by environmental factors (nutrition). The classical debate warned us that inheritance does not determine more than a mere response range (Crow Reference Crow1969; Hunt Reference Hunt1969) and argued for taking environmental interventions seriously, not unlike the role advocated to epigenetic unfolding by Charney.
These statistical discussions raised the methodological issue that when interpreting the twin data, the shared environment (see the argument of Charney about early shared environment and the onset of separation) and environmental similarity are not considered sufficiently. A left-wing French group of sociologists of science (Chappaz et al. Reference Chappaz, Coste and Chappaz1980) raised similar issues, when they criticized mixing statistical and professional regarding the additivity of variances.
Many twin researchers, who–due to their political preferences–believed in the deterministic role of environment well before postgenomics, argued for a more subtle use of twin data. Luria (Reference Luria1936) claimed that higher order functions are more under environmental control because identical and fraternal twins' elementary functions are more similar than their higher functions (e.g., voluntary memory). According to Luria, higher functions are under stricter environmental control and tend to converge with age. Zazzo (Reference Zazzo1955; Reference Zazzo1962), repeatedly argued that there is an important biological discrepancy between twin and singleton pregnancies–as Charney argues as well–and twins also have a peculiar social environment. Zazzo (Reference Zazzo1960) summarized the embryological and psychological peculiarities of twin development that could have been gathered before molecular genetics and modern behavior genetics were born.
These historical remarks are by far not questioning the arguments of Charney. My intention was to indicate that several issues raised by postgenomics research were present in discussions how genetics and “embriology” contribute to the unfolding of psychological individuality. The intense study of epigenetic unfolding as shown by Charney and by reviews like that of Zhanks and Meaney (Reference Zhanks and Meaney2010) indicate that to understand the implications of the striking landscape metaphor proposed by Waddington (Reference Waddington1942; Reference Waddington1957) to illustrate the concept of epigenesis (see Jablonka & Lamb [Reference Jablonka and Lamb2002] for a history of the concept), psychologists have to become aware of the possible new interpretation of their classical doubts regarding straightforward genetic determinism. One can find an interesting parallel between recent developments in postgenomics thought and classical issues of behavior genetics.
In addition to its specific claims regarding the dynamic nature of genetic determination of behavior, Charney's target article has done a great service in drawing our attention to the underlying principles and the history of the entire idea of the complexity of genetic determination. Charney, along with others (like Johnson et al. Reference Johnson, Penke and Spinath2011), rightly claims that the genetic determination of (among other things) behavior is complex at least in two regards. First, besides genes, gene expression is crucial. His second claim, that psychometric heritability is not the only issue of genetic determinism, should be seen in the context of the recent past. The historical reminder here goes back to the 1960s. That was the time when genetic determination reappeared in psychology, but in two rival and different forms. One was the innatism proposed by Chomsky (Reference Chomsky1959; Reference Chomsky1965; Reference Chomsky1968), mainly on analogy with ethology, suggesting that complex human behaviors may be under genetic control. Innatism was one way to overcome the “empty organism” metaphor of the behaviorists.
This kind of revival of genetic determinism was entirely uninterested in individual differences, as, for example, Chomsky's (Reference Chomsky1972a) intervention in the early intelligence debates showed. Innate organizing principles of language and other complex human achievements belong to “species-specific behaviors.” For Chomsky and his followers, this kind of genetic determination is by far not determinism in the traditional sense. Genetically determined language is not a constraint on thought; rather, by its structure it is unbound and unlimited, and therefore it also ensures the unlimited free development of humanity (Chomsky Reference Chomsky1972b; Reference Chomsky1988).
At roughly the same time, the issue of genetic determinism of human behavioral and intellectual individual differences became the focus of increasing scientific attention again. This opposing view focused on things differentiating individuals. They denied that the behaviorists' life history empiricism could be a possible way to explain individual differences. To explain individual differences, they referred to the Galtonian paradigm that proposed heredity to be crucial in determining individual differences in behavior and basically presupposed an additive role of nature (genetic) and nurture (environment). The followers of Galton considered interaction as a mere statistical term (for critical surveys, see McLafferty Reference McLafferty2006; Richardson & Spears Reference Richardson and Spears1972; Taylor Reference Taylor1980).
There is a third aspect of Galton's theory, namely, that it assumes one single feature of excellence. As we emphasized a decade ago:
In psychology Darwin's theory has taken two competing forms for more than a hundred years. The first is a conservative, deterministic approach based upon the theory of natural selection and the survival of the fittest. It stresses the need to reduce the dimensions of psychological variability by finding a small number of traits in which individuals differ from each other. If someone excels in these traits, he is considered to be fitter than others. The second approach is more tolerant, emphasizes development, and considers variability itself as an evolutionary asset. (Kovács & Pléh Reference Kovács and Pléh2000, p. 1)
The hot debate regarding the validity of the Galtonian paradigm started half a century ago by Jensen (Reference Jensen1969) claiming the genetic intellectual inferiority of African Americans. Interestingly, in addition to the social value issues, the debate concerned the statistical solidity of arguing on the basis of twin research towards the hereditary nature of individual and group differences. Way before postgenomics, the issues raised were similar to those regarding the relationships between postgenomics and heritability by Charney and by Johnson et al. (Reference Johnson, Penke and Spinath2011). Kagan (Reference Kagan1969) suggested that twin research does not allow us to make intergroup comparisons, and curiously enough, his examples, as well as those in the books edited by Richardson and Spears (Reference Richardson and Spears1972) and Block and Dworkin (Reference Block and Dworkin1976), consider the highly heritable trait of height as also being influenced and controlled by environmental factors (nutrition). The classical debate warned us that inheritance does not determine more than a mere response range (Crow Reference Crow1969; Hunt Reference Hunt1969) and argued for taking environmental interventions seriously, not unlike the role advocated to epigenetic unfolding by Charney.
These statistical discussions raised the methodological issue that when interpreting the twin data, the shared environment (see the argument of Charney about early shared environment and the onset of separation) and environmental similarity are not considered sufficiently. A left-wing French group of sociologists of science (Chappaz et al. Reference Chappaz, Coste and Chappaz1980) raised similar issues, when they criticized mixing statistical and professional regarding the additivity of variances.
Many twin researchers, who–due to their political preferences–believed in the deterministic role of environment well before postgenomics, argued for a more subtle use of twin data. Luria (Reference Luria1936) claimed that higher order functions are more under environmental control because identical and fraternal twins' elementary functions are more similar than their higher functions (e.g., voluntary memory). According to Luria, higher functions are under stricter environmental control and tend to converge with age. Zazzo (Reference Zazzo1955; Reference Zazzo1962), repeatedly argued that there is an important biological discrepancy between twin and singleton pregnancies–as Charney argues as well–and twins also have a peculiar social environment. Zazzo (Reference Zazzo1960) summarized the embryological and psychological peculiarities of twin development that could have been gathered before molecular genetics and modern behavior genetics were born.
These historical remarks are by far not questioning the arguments of Charney. My intention was to indicate that several issues raised by postgenomics research were present in discussions how genetics and “embriology” contribute to the unfolding of psychological individuality. The intense study of epigenetic unfolding as shown by Charney and by reviews like that of Zhanks and Meaney (Reference Zhanks and Meaney2010) indicate that to understand the implications of the striking landscape metaphor proposed by Waddington (Reference Waddington1942; Reference Waddington1957) to illustrate the concept of epigenesis (see Jablonka & Lamb [Reference Jablonka and Lamb2002] for a history of the concept), psychologists have to become aware of the possible new interpretation of their classical doubts regarding straightforward genetic determinism. One can find an interesting parallel between recent developments in postgenomics thought and classical issues of behavior genetics.