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heritability/​emergenesis directory

Some complex human traits like the physical traits of facial appearance or voice, or the psychological traits of leadership or genius appear highly genetically-caused, as shown by relatedness, while still being extremely rare and unpredictable. A proposal for resolving this is emergenesis: such genetic traits are highly nonlinear and non-additive (epistasis or dominance /    recessive), depending on many traits simultaneously, and failing otherwise, yielding familialness but rarity/​unpredictability—identical twins or clones will be highly similar, but siblings little more similar than the general population.

“Truly exceptional individuals, weak or strong, are, by definition, to be found at the extremes of statistical curves…Since each individual produced by the sexual process contains an unique set of genes, very exceptional combinations of genes are unlikely to appear twice even within the same family. So if genius is to any extent hereditary, it winks on and off through the gene pool in a way that would be difficult to measure or predict. Like Sisyphus rolling his boulder up to the top of the hill only to have it tumble down again, the human gene pool creates hereditary genius in many ways in many places only to have it come apart in the next generation.”

E.O. Wilson⁠, On Human Nature 1978

Links

“Genetics of Intellectual and Personality Traits Associated With Creative Genius: Could Geniuses Be Cosmobian Dragon Kings?”, Johnson & Jr. 2014

2014-johnson.pdf: “Genetics of Intellectual and Personality Traits Associated with Creative Genius: Could Geniuses Be Cosmobian Dragon Kings?”⁠, Wendy Johnson, Thomas J. Bouchard Jr. (2014; ⁠, ; backlinks; similar):

[Behavioral genetics discussion of eminence/​genius: intelligence, developmental processes, psychopathology, and creativity scales all contribute to accomplishment but leave much unexplained, in particular, the odd pattern of inheritance where genius runs in families but highly sporadically and not following any standard Mendelian or polygenic inheritance pattern.

The authors refer to the concept of ‘emergenesis’⁠, where emergenic traits are not additive combinations of subtraits (as is strongly the case for traits like intelligence) but rather are multiplicative combinations, which are epistatic at the genetic level. Because all subtraits must be present to have a chance of producing the overall trait, emergenic traits can be highly genetically influenced yet still rare and sporadically appearing within families. (The Wiley Handbook of Genius 2014, chapter 14)]

“The Mechanism of Emergenesis”, Lykken 2006

“The mechanism of emergenesis”⁠, D. T. Lykken (2006; ⁠, ; similar):

The intraclass correlations of monozygotic twins who were separated in infancy and reared apart (MZA twins) provide estimates of trait heritability, and the Minnesota Study of Twins Reared Apart [MZA: Bouchard et al 1990, ‘The sources of human psychological differences: the Minnesota study of twins reared apart’⁠, Science 250, 223–228] has demonstrated that MZA pairs are as similar in most respects as MZ pairs reared together.

Some polygenic traits—eg. stature, IQ, harm avoidance, negative emotionality, interest in sports—are polygenic-additive, so pairs of relatives resemble one another on the given trait in proportion to their genetic similarity.

But the existence and the intensity of other important psychological traits seem to be emergent properties of gene configurations (or configurations of independent and partially genetic traits) that interact multiplicatively rather than additively. Monozygotic (MZ) twins may be strongly correlated on such emergenic traits, while the similarity of dizygotic (DZ) twins, sibs or parent-offspring pairs may be much less than half that of MZ pairs. Some emergenic traits, although strongly genetic, do not appear to run in families.

MISTRA has provided at least two examples of traits for which MZA twins are strongly correlated, and DZA pairs correlate near zero, while DZ pairs reared together (DZTs) are about half as similar as MZTs.

These findings suggest that even more traits may be emergenic than those already identified. Studies of adoptees reared together (who are perhaps more common than twins reared apart) may help to identify traits that are emergenic, but that also are influenced by a common rearing environment.

[Keywords: epistasis, heritability, polygenic additivity, psychophysiology]

“Giftedness and Genetics: The Emergenic-Epigenetic Model and Its Implications”, Simonton 2005

“Giftedness and Genetics: The Emergenic-Epigenetic Model and Its Implications”⁠, Dean Keith Simonton (2005-05; similar):

The genetic endowment underlying giftedness may operate in a far more complex manner than often expressed in most theoretical accounts of the phenomenon. First, an endowment may be emergenic. That is, a gift may consist of multiple traits (multidimensional) that are inherited in a multiplicative (configurational), rather than an additive (simple) fashion. Second, the endowment may not appear all at once but, rather, will more likely unfold via an epigenetic process. These 2 complications have consequences regarding such aspects of giftedness as the likelihood of early signs, the appearance of early versus late bloomers, the distribution of giftedness in the general population, and the stability and continuity of gifts over the course of childhood and adolescence. These complexities lead to a 4-fold typology of giftedness that has important practical implications.

…To sum up, the consequences presented in Table 1 imply that the phenomenon of giftedness is far more complicated than often imagined. To the extent that the emergenic-epigenetic model describes the inheritance and development of giftedness, then a particular gift cannot be understood without first discovering if it is additive or multiplicative and if it is simple or complex. Naturally, the phenomenon of giftedness is even more intricate than even this model suggests. After all, I have only scrutinized the genetics of giftedness—on the developmental complexities of natural endowment. The analysis would become all the more complicated if I were to incorporate environmental factors explicitly into the developmental model. Nevertheless, it must be obvious that to the extent that a specific gift operates according to emergenic inheritance and epigenetic development, the complications are already far more prodigious than implied by most dictionary definitions.

[Note that the content of this paper almost completely overlaps with the almost-identically-titled Simonton 2005, “Genetics of Giftedness: The Implications of an Emergenic-Epigenetic Model”; you need not read the other. (Simonton is notorious for self-plagiarizing.)]

“Origins of Genius: Darwinian Perspectives on Creativity”, Simonton 1999

“Origins of Genius: Darwinian Perspectives on Creativity”⁠, Dean Keith Simonton (1999; ; backlinks; similar):

How can we account for the sudden appearance of such dazzling artists and scientists as Mozart, Shakespeare, Darwin, or Einstein? How can we define such genius? What conditions or personality traits seem to produce exceptionally creative people? Is the association between genius and madness really just a myth? These and many other questions are brilliantly illuminated in The Origins of Genius.

Dean Simonton convincingly argues that creativity can best be understood as a Darwinian process of variation and selection. The artist or scientist generates a wealth of ideas, and then subjects these ideas to aesthetic or scientific judgment, selecting only those that have the best chance to survive and reproduce. Indeed, the true test of genius is the ability to bequeath an impressive and influential body of work to future generations. Simonton draws on the latest research into creativity and explores such topics as the personality type of the genius, whether genius is genetic or produced by environment and education, the links between genius and mental illness (Darwin himself was emotionally and mentally unwell), the high incidence of childhood trauma, especially loss of a parent, amongst Nobel Prize winners, the importance of unconscious incubation in creative problem-solving, and much more.

Simonton substantiates his theory by examining and quoting from the work of such eminent figures as Henri Poincare⁠, W. H. Auden, Albert Einstein, Marie Curie, Charles Darwin, Niels Bohr⁠, and many others. For anyone intrigued by the spectacular feats of the human mind, The Origins of Genius offers a revolutionary new way of understanding the very nature of creativity.

“Emergenesis: Genetic Traits That May Not Run in Families: Genius”, Lykken et al 1992-page-8

“Emergenesis: Genetic Traits That May Not Run in Families: Genius”⁠, D. T. Lykken, Matthew McGue, A. Tellegen, T. J. Bouchard (1992; ; similar):

[Further discussion of “emergenesis” and relationship to genius: why are geniuses, while sometimes clearly affiliated with entire clans, so sporadic even within those? This is difficult to explain on any environmental or simple additive genetic grounds, suggesting that it may require entire complexes of exactly aligned genes and environmental factors.]

Human genius has always been a problem for both environmentalists and hereditarians to understand (Galton 1869; Kroeber 1944; Simonton 1988). There have been families of genius, of course—the Bernoullis and the Baths, the Darwins and the Huxleys, the musical Marsalis family—but it is the solitary genius, rising like a great oak in a forest of scrub and bramble, who challenges our understanding. Carl Friedrich Gauss, ranked with Archimedes and Newton as one of the “princes of mathematics”, had uneducated parents. His mother was illiterate, yet the boy had taught himself to read and to do simple arithmetic by the time he was 3 years old (Buhler, 1981).

…Suppose that Gauss or Ramanujan had been born with a healthy MZ twin who was spirited away to be reared by some country parson in Oxfordshire. Barring cholera or other accident, is it not likely that the parson’s surname too would now be immortal? Ramanujan died young without offspring; his parents and one brother apparently were unexceptional. Although Gauss provided rich stimulation and opportunity for his six offspring (by two different and highly cultivated wives), none of them distinguished themselves.2 But if the genius of these men was prefigured in their genes, why was it never manifested elsewhere in their lineage? The answer is, we think, that genius consists of unique configurations of attributes that cannot be transmitted in half helpings.

“Emergenesis: Genetic Traits That May Not Run in Families”, Lykken et al 1992

“Emergenesis: Genetic Traits That May Not Run in Families”⁠, D. T. Lykken, M. McGue, A. Tellegen, Thomas J. Bouchard Jr. (1992; ; similar):

Traits that are influenced by a configuration, rather than by a simple sum, of polymorphic genes may not be seen to be genetic unless one studies monozygotic twins (who share all their genes and thus all gene configurations) because such ‘emergenic’ traits will tend not to run in families. Personal idiosyncrasies that have been found to be surprisingly concordant among monozygotic twins separated in infancy and reared apart may be emergenic traits. More speculatively, important human traits like leadership, genius in its many manifestations, being an effective therapist or parent, as well as certain psychopathological syndromes may also be emergenic. These ideas reemphasize the importance of the role played in human affairs by genetic variation.

“Research With Twins: The Concept of Emergenesis”, Lykken 1982

“Research With Twins: The Concept of Emergenesis”⁠, D. T. Lykken (1982; ; similar):

Preliminary findings from an on-going study of monozygotic twins reared apart (MZA) and data from a larger sample of twins reared together (MZT and DZT), indicate a surprisingly strong influence of genetic variation on aptitudes, psychophysiological characteristics, personality traits and even dimensions of attitude and interest. For some of these variables, MZT and MZA twins show high intra-class correlations while DZT twins are no more similar than pairs of unrelated persons.

It is suggested that such traits are ‘emergenic’⁠, ie. that they are determined by the interaction—rather than the sum—of genetic influences. Emergenic traits, although perhaps strongly genetic, will not tend to run in families and for this reason have been neglected by students of behavior genetics.

For this and several other listed reasons, wider use of twins in psychological research is strongly recommended.

[Keywords: twins, behavior genetics, emergenesis, range correction, EEG spectra]

Miscellaneous