Random Developmental Variation of Human Phenotypic Traits, as Estimated by Fluctuating Asymmetry and Twin Studies

Öz

Random developmental variation, or developmental noise, contributes to total phenotypic variation in the human species. Despite exhortations to examine it, especially with respect to human behavior and intelligence, there has been little research specifically devoted to doing so. Random developmental variation can be estimated in studies of fluctuating asymmetry and comparisons of monozygotic and dizygotic twins. Estimation of random developmental variation requires that both genotype and environment be held constant. In a small sample of bilaterally symmetrical traits (dermatoglyphic ridge counts, digit lengths, ear lengths and widths), I show how the random developmental component can be estimated. In these traits, the percentage of total phenotypic variation attributable to developmental noise ranges from 3 percent to more than 25 percent. Moreover, for dermatoglyphic ridge counts, fluctuating asymmetry and twin comparisons give essentially the same estimates.

Anahtar Kelimeler

• Bilateral symmetry
• dermatoglyphics
• fluctuating asymmetry
• IQ
• morphometric traits
• phenotypic variation

Kaynakça

1. Bird, K. A. (2021). No support for the hereditarian hypothesis of the Black-White achievement gap using polygenic scores and tests for divergent selection. American Journal of Physical Anthropology, 2021, 1-12. google scholar
2. Danforth, C. H. (1919). Resemblance and difference in twins: twins that look and act alike attract attention first, while dissimilar ones are apt to be overlooked. Journal of Heredity, 10, 399-409. google scholar
3. Elowitz, M. B., Levine, A. J., Siggia, E. D., & Swain, P. S. (2002). Stochastic gene expression in a single cell. Science, 297, 1183-1186. google scholar
4. Falconer, D. S., & Mackay, T. F. C. (1996). Introduction to quantitative genetics (4th edition). Harlow, Essex, UK: Longman. google scholar
5. Finch, C. E., & Kirkwood, T. B. L. (2000). Chance, development, and aging. New York: Oxford University Press. google scholar
6. Friedman, N. P., Banich, M. T., & Keller, M. C. (2021). Twin studies to GWAS: there and back again. Trends in Cognitive Sciences. http://dx.doi.org/10.1016/j.tics.2021.06.007 google scholar
7. Gartner, K. (1990). A third component causing random variability beside environment and genotype. A reason for the limited success of a 30 year long effort to standardize laboratory animals? Laboratory Animals, 24, 71-77. google scholar
8. Graham, J. H. (2020). Fluctuating asymmetry and developmental instability, a guide to best practice. Symmetry, 13, 9. https://dx.doi.org/10.3390/sym13010009 google scholar

9. Graham, J. H. (2021). Nature, nurture, and noise: Developmental instability, fluctuating asymmetry, and the causes of phenotypic variation. Symmetry, 13, 1204. https://doi.org/10.3390/sym13071204 google scholar
10. Graham, J. H., Emlen, J. M., & Freeman, D. C. (1993). Antisymmetry, directional asymmetry, and dynamic morphogenesis. Genetica, 89, 121-137. google scholar
11. Graham, J. H., Emlen, J. M., & Freeman, D. C. (2003). Nonlinear dynamics and developmental instability. In M. Polak (Ed.), Developmental instability: Causes and consequences (pp. 35-50). New York: Oxford University Press. google scholar
12. Graham, J. H., Emlen, J. M., Freeman, D. C., Leamy, L. J., & Kieser, J. A. (1998) Directional asymmetry and the measurement of developmental instability. Biological Journal of the Linnean Society, 64, 1-16. google scholar
13. Graham, J. H., & Özener, B. (2016). Fluctuating asymmetry of human populations: A review. Symmetry, 8, 154. https://dx.doi.org/10.3390/sym8120154 google scholar
14. Graham, J. H., Raz, S., Hel-Or, H., & Nevo, E. (2010). Fluctuating asymmetry: methods, theory, and applications. Symmetry, 2, 466-540. https://dx.doi.org/10.3390/sym2020466 google scholar
15. Holt, S. B. (1952). The genetics of dermal ridges: Bilateral asymmetry in finger ridge-counts. Annals of Eugenics, 17, 211-231. https://doi.org/10.1111/j.1469-1809.1952.tb02513.x google scholar
16. Jolicoeur, P. (1963). Bilateral symmetry and asymmetry in limb bones of Martes americana and man. Revue Canadienne de Biologie, 22, 409-432. google scholar
17. Kozhara, A. V. (1989). On the ratio of components of phenotypic variances of bilateral characters in populations of some fishes. Genetika, 25, 1508-1513. google scholar
18. Kozhara, A. V. (1994). Phenotypic variance of bilateral characters as an indicator of genetic and environmental conditions in bream Abramis brama (L.) (Pisces, Cyprinidae) populations. Journal of Applied Ichthyology, 10, 167-181. https://doi.org/10.1111/j.1439-0426.1994.tb00156.x google scholar
19. Lajus, D. L, Graham, J. H., & Kozhara, A. V. (2003). Developmental instability and the stochastic component of total phenotypic variance. In M. Polak (Ed.), Developmental instability: Causes and consequences (pp. 343-363). New York: Oxford University Press. google scholar
20. Leamy, L. (1984). Morphometric studies in inbred and hybrid house mice. V. Directional and fluctuating asymmetry. American Naturalist, 123, 579-593. https://doi.org/10.1086/284225 google scholar
21. Lee, J. J., Wedow, R., ... & Cesarini, D. (2018). Gene discovery and polygenic prediction from a genome-wide association study of educational attainment in 1.1 million individuals. Nature Genetics, 50, 1112-1121. https://doi.org/10.1038/s41588-018-0147-3 google scholar
22. Özener, B., & Graham, J. H. (2014). Growth and fluctuating asymmetry of human newborns: Influence of inbreeding and parental education. American Journal of Physical Anthropology, 153, 45-51. google scholar
23. Palmer, A. R., & Strobeck, C. (1986). Fluctuating asymmetry: measurement, analysis, patterns. Annual Review of Ecology and Systematics, 17, 391-421. google scholar
24. Pinker, S. (2003). The blank slate: The modern denial of human nature: New York, NY: Penguin. google scholar
25. Pinker, S. (2004). Why nature & nurture won’t go away. Daedalus, 133, 5-17. google scholar
26. Plomin, R., & Loehlin, J. C. (1989). Direct and indirect IQ heritability estimates: a puzzle. Behavior Genetics, 19, 331-342. google scholar
27. Rao, D., Morton, N., Lalouel, J., & Lew, R. (1982). Path analysis under generalized assortative mating: II. American IQ. Genetics Research, 39, 187-198. google scholar
28. Raser, J. M., & O’Shea, E. K. (2005). Noise in gene expression: origins, consequences, and control. Science, 309, 2010-2013. google scholar
29. Robin, E. D., & Wong, R. (1988). Mitochondrial DNA molecules and virtual number of mitochondria per cell in mammalian cells. Journal of Cellular Physiology, 136, 507-513. https://doi.org/10.1002/ jcp.1041360316 google scholar
30. Schroeder, M. (1990). Fractals, chaos, power laws: Minutes from an infinite paradise. New York, NY: W. H. Freeman. google scholar
31. Shen, H., & Feldman, M. W. (2020). Genetic nurturing, missing heritability, and causal analysis in genetic statistics. Proceedings of the National Academy of Sciences, 117, 25646- 25654. https://doi. org/10.1073/pnas.2015869117 google scholar
32. Tashman, L. J. & Lamborn, K. R. (1979). Ways and means of statistics. New York, NY: Harcourt Brace Jovanovich google scholar
33. Tzagoloff, A. (2012). Mitochondria. London: Springer Science & Business Media. google scholar
34. Williams, G. P. (1997). Chaos theory tamed. Washington, D. C.: Joseph Henry Press. google scholar
35. Wolfe, S. L. (1993). Molecular cell biology. Belmont, CA: Wadsworth. google scholar
36. Wright, S. (1920). The relative importance of heredity and environment in determining the piebald pattern of guinea-pigs. Proceedings of the National Academy of Sciences, 6, 320-332. google scholar
37. Zheng, Z. & Cohn, M. J. (2011). Developmental basis of sexually dimorphic digit ratios. Proceedings of the National Academy of Sciences, 108, 16289-16294. google scholar