Abstract
A recent report by G. Clark points to a sustained persistence of social status in England that extends vertically across several generations and horizontally across many levels of kinship. We seek to put his findings in historical perspective. We do so by relating them to two lines of thinking related to biological inheritance. One predated the rediscovery of Mendel’s work and led to the field of quantitative genetics, which dealt on the whole with quasi-continuously varying traits. The other is based on the rediscovery itself and led to a reconciliation between quantitative genetics and discrete Mendelian elements of heredity. Both were enmeshed with the supposed need for, and societal consequences of, eugenics and assortative mating. Also on both issues, the significant ideas can be traced to R. A. Fisher, inspired in one case by F. Galton and in the other by J. A. Cobb, with strong support for Galton and Cobb coming from Karl Pearson. Clark’s findings point to societal stratification, and assortative mating for wealth is a straightforward hypothesis to account for it. However, it should be noted that the findings support, but do not prove, the hypothesis.
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Notes
He explained why as follows: ‘We greatly want a brief word to express the science of improving stock, which is by no means confined to questions of judicious mating, but which, especially in the case of man, takes cognisance of all influences that tend in however remote a degree to give to the more suitable races or strains of blood a better chance of prevailing speedily over the less suitable than they otherwise would have had. The word eugenics would sufficiently express the idea ...’ (Galton 1883, footnote on p.17).
Other exchanges on the subject are worth noting: https://www.nytimes.com/2005/03/14/opinion/a-family-tree-in-every-gene.html, http://raceandgenomics.ssrc.org/Lewontin/.
Selective breeding carried out to improve useful traits, both physical and behavioural, was an old practice among plant and animal breeders; Darwin coined the term ‘natural selection’ by analogy with the artificial selection carried out by animal breeders, especially pigeon fanciers. In the human context, Galton’s thinking had predecessors, notably Quetelet (Jahoda 2015).
Cobb uses ‘fit’ in the colloquial sense of ‘having made it’, of course, and in general he refers to group mean fitness, not individual fitness. Going by their contribution to succeeding generations, as we would in the context of selective differences, the ‘less fit’ classes of Cobb could in fact be the fitter. Fitness as a property of the individual can really only be measured in retrospect, and is complicated to measure even then, as the existence of the grandchildless gene in various species of Drosophila illustrates (Spurway 1948; Mariol 1981).
‘The mere possession of wealth, as opposed to other qualities, seems to have more influence than usual in determining social position.’
Which was, in Fisher’s words, that ‘The socially lower classes have a birth-rate, or, to speak more exactly, a survival rate, greatly in excess of those who are, on the whole, distinctly their eugenic superiors.’ A recent report claims to find that in Great Britain, genetics, wealth and infertility go together: ‘Consistently over time, polygenic scores that predict higher earnings, education and health also predict lower fertility.’ (Hugh-Jones and Abdellaoui 2022).
In particular, that Mendelian genetics provided a sufficient basis for explaining evolution by natural selection.
Fisher himself set so much store by the significance of those chapters as to write in a letter to J. B. S. Haldane (while commenting on reviewers of the book), ‘I do not think they are wrong scientifically in stressing the purely biological parts for these constitute the scientific foundation of the rest, but the human inferences, if well founded, are of such practical importance that they will certainly be the ultimate centre of interest.’ (Fisher to Haldane, 17 December 1930; Bennett (ed.), p. 213).
‘Permanent civilization’ meaning a society that sustained itself stably without suffering the dysgenic consequences indicated by Cobb.
‘Consequently it is impossible to avoid the conclusion that, in a society in which members of small families are on the average at a social advantage compared to members of large families, the parents being in other respects equivalent, society will become graded, not only in respect of physiological infertility, but much more rapidly and more steeply graded in respect of those temperamental differences which conduce to celibacy, postponement of marriage and birth limitation’ (1958 2nd ed., p. 253).
Galton’s analysis dealt with regression, not correlation, the significance of which was realized by Pearson (1920).
Bulmer (1998) discusses what we now recognize as the missteps and mistakes made by Galton (conflating correlation with ‘contribution’, ‘one-third as near’, etc.). In 1909, Weinberg made the point that the distinction between discrete and quasi-continuous inheritance was not absolute, but his reasons—which included a lack of sharpness with regard to the limits of expression of a trait, especially when it was influenced by several genes (i.e., polygeny)—were only partly the same (Weinberg 1909, p.385). J. G. Kölreuter and K. Pearson have been credited for recognising that traits could be polygenic, but that appears to be the result of a failure to treat the observation of ‘continuous variation’ on a separate footing from its explanation on the basis of polygeny. Galton came closer to the explanation, and Weinberg (who also made a number of other prescient remarks) enunciated it unambiguously (Weinberg 1909).
Having demonstrated that the law of ancestral heredity was a direct consequence of polygenic inheritance, Weinberg concluded that the fight between biometricians and Mendelians was entirely without a basis. Pearson (1904) too considered how correlations among relatives and quasi-continuous variation could be consistent with Mendel’s rules, but for some reason he restricted himself to two alleles in a 1:1 proportion at each locus. It is worth noting that Mendel himself had pointed out that if many factors (genes) were behind the same character, their binomial (random) assortment would give rise to quasi-continuous variation (Mendel 1866).
As a result, a child can resemble a particular parent not only on account of receiving that parent’s genes, but also indirectly, via the other parent—as long as the resemblance in the trait between the parents has a genetic basis, at least in part. Fisher (1918) deals only with positive correlation. The concept of variance and its significance were first brought out by Fisher in the same paper. Additive effects amount to making the simplest assumption, statistically speaking, of the manner in which two causes interact. Fisher’s (1918) analysis is remarkably comprehensive; he had thought hard about a range of potential influences on a trait, and seized on the additive components because of likely importance as well as ease of analysis. Later, perhaps stimulated by his critics, he went further, in his analysis of what happens when one allele replaces another (Fisher 1941).
Unless it is one of the ‘few ephemeral papers of my own’ that he alludes to, as part of his contributions to ‘sociological theory’ (Fisher 1958, p.247).
Few ideas in population genetics have been as written about, or as misunderstood, as Fisher’s ‘fundamental theorem’. Loosely put, the theorem states that the increase in mean fitness of a population attributable to natural selection is always positive or zero. In that sense, it hints at the existence of an ‘arrow of time’ pointing in the direction that evolution by natural selection is compelled to take. Fisher, who had studied under the physicist James Jeans, intended to draw an analogy between the roles played by the mean fitness of a population in evolution and entropy in thermodynamics. See Edwards (1994, 2002) for a clear exposition of what Fisher was saying.
Besides endogamy, there is, to be sure, a pernicious aspect to the caste system, captured in the description that it is marked ‘not merely by inequality’ but by ‘graded inequality...There is a kind of ascending scale of hatred and a descending scale of contempt.’ (Ambedkar 1979, p.167).
Simple models of repeated interactions between individuals involving the transfer of wealth show that even when the direction of an exchange is ‘random’, extreme stratification can result. To the extent that the models have a basis in reality, they would seem to point to the necessity for checks on individual behaviour (Hayes 2002).
For instance, his 'family allowances' proposal for subsidising the breeding of the more intelligent (Fisher 1930, p. 273 onwards) and many citations in Bennett (1983) from p. 34 onwards. Many aspects of Fisher’s masterpiece remain contentious, e.g. his reason for the decline of infanticide in ancient times (see Mayo 2018) but they are not relevant here.
The simplest model has been termed a ‘yard sale’ (Boghosian 2019). It involves a population of individuals who have the same assets to begin with. Two individuals are picked at random and exchange their assets. One of them is designated the winner and the other, the loser, again at random. If he is the richer of the two to begin with, a fixed percentage of the loser’s assets gets transferred to him; if the winner is the poorer of the two before the exchange, he gets the same fixed percentage of the loser’s, therefore richer person’s, assets. (The terms richer and poorer are irrelevant for the very first exchange.) The system seems tailor-made to ensure equality, but the outcome shows otherwise.
References
Ambedkar B. R. 1944 The annihilation of caste, 3rd edition., Columbia University Press, New York.
Ambedkar B. R. 1979 Dr. Babasaheb Ambedkar: writings and speeches, vol. 1 (Education Department, Govt. of Maharashtra: ISBN 978-93-5109-064-9).
Atkinson A. B. 2015 Inequality what can be done?, Harvard University Press, Cambridge.
Bennett J. H. 1983 Natural selection, heredity, and eugenics: Including selected correspondence of R.A. Fisher with Leonard Darwin and others, Clarendon Press, Oxford.
Bodmer W., Bailey R. A., Charlesworth B., Eyre-Walker A., Farewell V., Mead A. et al. 2021 The outstanding scientist, R.A. Fisher: his views on eugenics and race. Heredity 126, 565–576.
Boghosian B. M. 2019 The inescapable casino. Sci. Am. 321, 70–77.
Bouchard C., Pérusse L. and Leblanc C. 1990 Using MZ twins in experimental research to test for the presence of a genotype-environment interaction effect. Acta Genet. Med. Gemellol. 39, 85–89.
Burt C. H. 2023 Challenging the utility of polygenic scores for social science: Environmental confounding, downward causation, and unknown biology. Behav. Brain Sci. 46(e207), 1–66.
Chakraborti A. 2002 Distributions of money in model markets of economy. Int. J. Modern Phy. 13, 1315–1321.
Clark G. 2023 The inheritance of social status: England, 1600 to 2022. Proc. Natl. Acad. Sci. USA 120, e2300926120.
Clark G. and Cummins N. 2013 Surnames and social mobility: England, 1230-2012. Economic History Working Papers No: 181/2013. London School of Economics. WP181 revised.pdf (lse.ac.uk) accessed 3 November 2023.
Cobb J. A. 1913 Human fertility. Eugen. Rev. 4, 379–382.
Deary I. J., Johnson W. and Houlihan L. M. 2009 Genetic foundations of human intelligence. Hum. Genet. 126, 215–232.
Edwards A. W. F. 1994 The fundamental theorem of natural selection. Biol. Rev. 69, 443–474.
Edwards A. W. F. 2002 The fundamental theorem of natural selection. Theor. Popul. Biol. 61, 335–337.
Edwards A. W. F. 2003 Lewontin’s Fallacy. BioEssays 25, 798–801.
Edwards A. W. F. 2020 The thoughtful eugenist. R.A. Fisher’s eugenic concerns. Link at http://www.senns.uk/FisherWeb.html.
Emrich J., Francesconi M. and Siedler T. 2005 Intergenerational mobility and assortative mating. IZA Discussion Papers 1847. Institute for the Study of Labour, Bonn.
Fisher R. A. 1914 Some hopes of a eugenist. Eugen. Rev. 309-315.
Fisher R. A. 1918 The correlation between relatives on the supposition of Mendelian inheritance. Trans. R. Soc. Edinburgh 52, 399–433.
Fisher R. A. 1930 The genetical theory of natural selection, Oxford University Press; 2nd revised edition by Dover Publications in 1958.
Fisher R. A. 1941 Average excess and average effect of a gene substitutions. Ann. Eugen. 11, 55–63.
Galton F. 1883 Inquiries into human faculty and its development, p. 17. Macmillan https://pure.mpg.de/rest/items/item_2323042_3/component/file_2323043/content.
Galton F. 1889 Natural inheritance. Macmillan, London.
Galton F. 1897 The average contribution of each several ancestor to the total heritage of the offspring. Proc. R. Soc. London 61, 401–413.
Galton F. 1904 Eugenics: its definition, scope and aims. Am. J. Sociol. X, 1–25.
Hayes B. 2002 Follow the money. Am. Sci. 90, 400–405.
Hugh-Jones D. and Abdellaoui A. 2022 Human capital mediates natural selection in contemporary humans. Behav. Genet. 52, 205–234.
Jacquard A. 1983 Heritability: one word, three concepts. Biometrics 39, 465–477.
Jahoda G. 2015 Quetelet and the emergence of the behavioral sciences. Springerplus 4, 473, https://doi.org/10.1186/s40064-015-1261-7.
Joseph J. 2001 Separated twins and the genetics of personality differences: a critique. Am. J. Psychol. 114, 1–30.
Kempthorne O. 1957 An introduction to genetic statistics, John Wiley, New York.
Kempthorne, 1978 Logical, epistemological and statistical aspects of nature-nurture data interpretation. Biometrics 34, 1–23.
Kevles D. J. 1998 In the name of eugenics, Harvard University Press, London.
Lande R. 2009 The genetic correlation between characters maintained by selection, linkage and inbreeding. Genet. Res. 44, 309–320.
Lee J. J. 2023 The heritability and persistence of social class in England. Proc. Natl. Acad. Sci. USA 120, e2309250120.
Lewontin R. C. 1972 The apportionment of human diversity. In Evolutionary Biology 6 (ed. T. Dobzhansky, M. K. Hecht and W. C. Steere) pp. 381–398. Appleton-Century-Crofts, New York.
Mariol M.-C. 1981 Genetic and developmental studies of a new grandchildless mutant of Drosophila melanogaster. Mol. Gen. Genet. 181, 505–511.
Mayo O. 2011 Interaction between genotype and environment: a tale of two concepts. Trans. R. Soc. S. Aust. 135, 113–123.
Mayo O. 2018 Evolution by natural selection and ethics. What in evolution has ethical implications? Stuttgart, Gebr. Borntraeger Verlagsbuchhandlung.
Mendel G. 1866 Versuche über Plflanzenhybriden. Verhandlungen des naturforschenden Vereines in Brünn, Bd. IV für das Jahr 1865, Abhandlungen, 3–47. (English translation by W. Bateson, reproduced with minor corrections in http://www.esp.org/foundations/genetics/classical/gm-65.pdf).
Mills M. C. and Tropf F. C. 2020 Sociology, genetics, and the coming of age of sociogenomics. Ann. Rev. Sociol. 46, 553–581.
Nettle D. and Pollet T. V. 2008 Natural selection on male wealth in humans. Am. Nat. 172, 658–666.
Paul D. 1984 Eugenics and the left. J. Hist. Ideas 45, 567–590.
Pearson K. 1904 Mathematical contributions to the theory of evolution.—XII. On a generalised Theory of alternative Inheritance, with special reference to Mendel’s laws. Phil. Trans. R. Soc. London, A 203, 53–86.
Pearson K. 1920 Notes on the history of correlation. Biometrika 13, 25–45.
Posthuma D., Luciano M., Geus E. J., Wright M. J., Slagboom P. E., Montgomery G. W. et al. 2005 A genome-wide scan for intelligence identifies quantitative trait loci on 2q and 6p. Am. J. Hum. Genet. 77, 318–326.
Rao V. and Nanjundiah V. 2011 J. B. S. Haldane, Ernst Mayr and the Beanbag genetics dispute. J. Hist. Biol. 44, 233–281.
Rosenberg N. A., Pritchard J. K., Weber J. L., Cann H. M., Kidd K. K., Zhivotovsky L. A. et al. 2002 Genetic structure of human populations. Science 298, 2381–2385.
Safdar M. R., Akram M., Sher F. and Rehman A. 2021 Socioeconomic determinants of caste-based endogamy: a qualitative study. J. Ethn. Cult. Stud. 8, 39–54.
Sarkar S. 2023 GWASs and polygenic scores inherit all the old problems of heritability estimates. Behav. Brain Sci. 46, e227.
Savage J. E., Jansen P. R., Stringer S., Watanabe K., Bryois J., de Leeuw C. A. et al. 2019 Genome-wide meta-analysis of 269,867 individuals identifies new genetic and functional links to intelligence. Nat. Genet. 50, 912–919.
Schwartzentruber J., Cooper S., Liu J.Z., Barrio-Hernandez I., Bello E., Kumasaka N, et al. 2021 Genome-wide meta-analysis, fine-mapping and integrative prioritization implicate new Alzheimer’s disease risk genes. Nat. Genet. 53, 392–402.
Spurway H. 1948 Genetics and cytology of Drosophila subobscura. IV An extreme example of delay in gene action, causing sterility. J. Genet. 49, 126–140.
Tabery J. G. 2004 The evolutionary synthesis’ of George Udny Yule. Hist. Biol. 37, 73–101.
Tabery J. 2008 RA Fisher, Lancelot Hogben, and the origin(s) of genotype–environment interaction. J. Hist. Biol. 41, 717–761.
Weinberg W. 1909 Über Vererbungsgesetze beim Menschen. Z. Vererbung. 1, 377-392 and 440–460.
Young A. I., Benonisdottir S., Przeworski M. and Kong A. 2019 Deconstructing the sources of genotype-phenotype associations in humans. Science 365, 1396–1400.
Acknowledgements
We are grateful to M. H. Cohen, A. W. F. Edwards, D. P. Kasbekar, P. P. Majumder and an anonymous referee for their comments on an earlier version of this paper. VN wishes to particularly thank A. W. F. Edwards for introducing him to the work of J. A. Cobb and his influence on R. A. Fisher. OM thanks N. G. Martin, R. Nolan and J. A. Sved for helpful discussion.
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Mayo, O., Nanjundiah, V. Reflections on assortative mating, social stratification, and genetics. J Genet 103, 15 (2024). https://doi.org/10.1007/s12041-024-01467-9
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DOI: https://doi.org/10.1007/s12041-024-01467-9