Historical Variability In Heritable General Intelligence

Michael A. Woodley, Aurelio Jose Figueredo

• Publisher: University of Buckingham Press
• Year: 2013
• ISBN:
  9781789551365
• Topic: Biological Sciences
• Subtopic: Genetics & Genomics
• Index: Biological Sciences

It is easy for us to believe that as a society we are getting smarter, at least as measured by IQ tests. This supposed improvement, the Flynn Effect, suggests that each generation is brighter than the last.

If this improvement in intelligence is real we should all be much, much brighter than the Victorians. However, the researchers of this ground-breaking study find the reverse to be true- the Victorians were cleverer than us! IQ tests may be effective at picking out the brightest, but they are not reliable benchmarks of performance over more than a century.

Historical Variance records the exploration of the Flyyn effect hypothesis, which included the use of high-quality instruments to measure simple reaction times (a recognised predictor of intelligence) in a meta-analytic study.

The conclusions are very sobering: far from speeding up, we are slowing down. A decline in general intelligence (a loss equivalent to about 14 IQ points) since Victorian times may have resulted from the presence of dysgenic fertility. These findings, as detailed in Historical Variance, strongly indicate that the Victorians were substantially cleverer than we are today...

1. INTRODUCTION

One of the most controversial findings in intelligence research is the existence of negative correlations between IQ and fertility. As long ago as the 19^th century, it was feared that civilization had gone too far in alleviating the Darwinian pressures keeping those with ‘valuable’ traits, such as high-intelligence, good health and character in high-fertility, whilst supressing the same amongst those endowed with low levels of these traits (e.g. Darwin, 1871; Galton, 1869). This fear was manifest despite the absence of either sophisticated psychometric and anthropometric measures of these ‘valuable traits’ or compelling data indicating that their levels had actually changed. Early in the 20^th century, the term ‘dysgenics’ was coined to describe this phenomenon (Saleeby, 1913, 1914; Starr-Jordan, 1915).

Dysgenics was frequently defined in normative terms, with negative changes in the level of traits such as IQ being described as ‘socially undesirable’. The term itself literally means ‘bad-breeding’. The no less normatively loaded antonym of dysgenics, ‘eugenics’ (meaning good-breeding) was coined even earlier (Galton, 1883). The idea was to use eugenic measures to counter the socially undesirable consequences of dysgenic fertility.

When attempting a scientific discussion of issues such as dysgenics and eugenics, we believe that it is very important to define the relevant terms with greater precision than is typically done, as this field of research is fraught with many misunderstandings. In doing so, however, we will of necessity be making certain interpretations regarding the way that some of the more politically-charged terms have been used historically, and we will be providing evidence for those interpretations.

The first ‘term of art’ that needs clarification is fitness, as opposed to selection. Selection is a process and fitness is the outcome of that process. Fitness is defined in population biology as gene-copying success under a particular regime of selection, although it is sometimes used colloquially as the heritable phenotypic traits that confer such an advantage. As a consequence of the many misunderstandings of the word “fitness”, we limit our use of that term in this monograph exclusively to instances where fitness is explicitly invoked as an outcome, and retain “selection” for where we describe the differentials in survival and reproduction produced by different selective processes, or selective pressures, such as within-group and between-group competition.

The total fitness (f), or gene-copying success, achieved by an organism is the product of three terms that determine the survival probability of the organism’s genome, integrated over however many bouts of reproduction it engages in over its lifetime: the number of offspring produced (n_o), the expected longevity of those offspring (l_o), and the coefficient of genetic relationship between the parent and its offspring (r_po):

f = ∫_b(n_o)(l_o)(r_po)

The function f represents the “fitness”, or copying success of the entire genome over a specified period of time (such as the entire lifespan if lifetime fitness is desired), but also gives us the number of copies of any individual gene (technically, allele) surviving to any given point in time at which offspring survivorship is assessed. This is because the coefficient of genetic relationship (r_po) is equal to the probability of any given offspring carrying that particular gene, by the application of Bernoulli's Theorem. The probability of that particular gene surviving (r_po) is then multiplied by the number of offspring being produced (n_o) and the probability of those offspring surviving to a certain point in time (l_o). It is necessary to include the term (r_po) as a variable in this expression because it is not always equal to 0.50, even in sexually-reproducing diploid species, especially under conditions of assortative mating. This product represents the instantaneous replication of a genome achieved by any single bout of reproduction, and the integral over time sums those instantaneous products over the lifespan (for a complete mathematical derivation of this formulation, see Figueredo & Wolf, 2009; Wolf & Figueredo, 2011).

The second ‘term of art’ that needs clarification is fertility, as opposed to fecundity, owing to the fact that they are used in the biological sciences in a more specialized way than in general discourse. Fertility is defined as the per capita rate of the number of children actually born to each woman (typically operationalized as number of children per 1000 women) in the population. Sometimes, the denominator of this expression is limited to a certain subgroup of women. For example, the general fertility rate includes the number of children born to women between the ages of 15 and 44; the age-specific fertility rate includes those born to women of a given age cohort (e.g., 25 years old); the completed fertility rate includes those born to women of a given cohort until the end of their reproductive careers (e.g., 44 years old). The distinction that causes the most confusion, however, is not between the subset of women being considered, but between the concepts of fertility and fecundity, which are commonly used interchangeably. Fecundity, however, is technically defined as a woman’s potential or ability to produce children, not her actual reproductive output, also known as reproductive success. Thus, a woman using contraceptives may have a high fecundity but a low fertility. Therefore, when we observe that higher-IQ women have lower fertility than lower-IQ women, for whatever reason, we do not mean that they lack the capacity to reproduce, but only that they generally do so at a lower rate.

1.1 Dysgenesis and Eugenesis Redefined

In considering the concepts of dysgenics and eugenics, we contend that new definitions are needed because the traditional usage borders on the logically incoherent and quite commonly crosses the line into becoming technically misleading. As was mentioned in the previous section, dysgenics is typically described in terms of the potential for ‘socially desirable’ traits (such as intelligence, but also health and desirable personality or ‘good character’), the carriers of which are frequently described as being ‘more fit’ (e.g. Lynn, 2001; Nyborg, 2012) to become scarcer in a population over time owing to differential patterns of fertility disfavoring these traits. The outcome of dysgenic fertility is sometimes also termed dysgenesis (Herrnstein & Murray, 1994). The antonym of dysgenesis is of course eugenesis, which describes the increased prevalence of the ‘fitter’ carriers of ‘socially desirable’ traits entailed by the presence of either eugenic natural or artificial selection pressures (i.e. due to the presence of a eugenics program). From the perspective of evolutionary theory, however, it presents something of a logical paradox to assert that phenotypes that are ‘less fit’ are systematically out-reproducing those that are ‘more fit’. This construction appears to fly in the face of the fundamental biological definition of Darwinian fitness, because the carriers of these presumably ‘undesirable’ traits are generally described as increasing their numbers at the expense of those with the presumably ‘desirable’ ones. For that reason, among others, some have concluded that what constitutes ‘social desirability’ is no more than a cultural construction, meaning that it represents an arbitrary value judgment by specific groups or individuals, and that these characterizations might be biased in a self-serving manner, consistent with their social, economic, or reproductive interests (Mackintosh, 2002).

To be able to employ the words ‘dysgenic’, ‘eugenic’ and related terms more productively in scientific discourse (if one wishes to retain them at all, given that the words imply ‘undesirable’ and ‘desirable’ outcomes respectively), we therefore need to provide a more objective reframing based on the evolutionary ramifications of the phenomena. We propose that this can be accomplished by viewing these processes within the framework of a multi-level selection model, which conceives of a ‘dysgenic trait’ as one that has the potential to confer a competitive advantage or benefit at an individual level, but imposes a competitive disadvantage or cost at the group level. In this multilevel selection model, ‘dysgenic fertility’ may thus occur when individuals bearing such traits are favored in within-group competition by individual-level selection, but the social groups to which they belong are disfavored in between-group competition as a consequence in group-level selection (Cattell, 1972; Figueredo, 2012). Conversely a ‘eugenic trait’ is one that has the potential to confer a competitive advantage at the group level, while not necessarily conferring an advantage at the individual level, and possibly even producing a competitive disadvantage in individual selection (Figueredo, 2012; Hamilton, 2000). Such traits might include ‘heroic’ levels of altruism during a time of war, where the principal beneficiary is the group rather than the individual.

The multi-level selection model dates back to Charles Darwin (1871), furthermore eugenicists in the early 20^th century were clearly cognisant of the implications of multi-level selection for the proliferation or reduction of traits deemed to be ‘socially desirable’ (e.g. Krischel, 2012). A major line of supporting evidence for this comes from the documentary historical evidence indicating that during the heyday of the eugenics movement in the 1900’s to the 1930’s and even more recently, many of its most forceful advocates were politically collectivistic, irrespective of whether they believed in eugenics as a means of bettering a nation or ethnic grouping, or whether they were universalists, who believed that eugenic measures had to be adopted by mankind as a whole (Glad, 2006). Implicit, and sometimes also explicit in their pronouncements was the idea that eugenic measures must serve the collective good, if the collectivity is to prosper in the long run. A classic universalist eugenics advocacy document is the Social Biology and Population Improvement document (commonly known thereafter as the Eugenicist’s Manifesto), which was produced by a group of eminent British and American biologists and geneticists (including Darlington, Haldane, Huxley, Dobzhansky, Muller, Price and Waddington amongst others) under the group-name of Science Service (1939). These biologists were explicit in their collectivism, stating for example that “some effective sort of federation of the whole world, based on the common interests of all its peoples” (p. 521) will be necessary for ameliorating the “economic and political conditions which foster antagonism between different peoples, nations and ‘races’” (p. 521; quotes in original), which they in turn saw as a threat to the adoption of eugenic measures. Another potential hindrance to their eugenical aims were the economic social and economic conditions having the potential to impose opportunity costs on high-ability women in terms of childrearing capacity. These could only be alleviated via “an organization of production primarily for the benefit of consumer and worker” (p. 521), which would in turn necessitate that “dwellings, towns and community services generally are reshaped with the good of children as one of their main objectives” (p. 521). Even the suite of traits considered by these eugenicists to be socially desirable include a kind of social or group mindedness, or “temperamental qualities which favour fellow-feeling and social behaviour rather than those… which make for personal ‘success’, as success is usually understood at present” (p. 521). Another, relatively more recent and also more explicit example of collectivist eugenic advocacy can be seen in the writings of Raymond B. Cattell (1972, 1987) on the topic of Beyondism – an ethical-religious system designed to promote eugenical aims and spread eugenical virtues via the encouragement of competition between different ethno-cultural groups. Cattell (1972) was the first to articulate a multi-level selection basis for thinking about the distinction between eugenic and dysgenic traits using modern evolutionary terminology, illustrating it thusly:

“For the processes of within-group individual selection and between-group selection of social organisms are not merely potentially independent, producing different results, but especially in regard to such vital traits as superego strength and self-sacrificing tendencies systematically undoing each other. Certainly one can see that it is easily possible for the within-group selection of individuals, i.e., the relative survival rates among individuals, to produce genetic types and tendencies to behavioral habits highly favorable to selfish individual survival but in the end incompatible with the survival of the group.” (p. 84).

In a subsequent work Cattell (1987) illustrates his belief in the need for collective agency in the realization of group-level eugenic outcomes, stating that:

“A group positively planning well for its future will employ all three of the above: (1) differential birth/death rates, (2) rhythms of segregation and well-chosen hybridization, and (3) creation of mutations along with genetic engineering… These methods we need to use toward group goals to bring about by a collective movement of its citizens (a) survival of the group, and (b) launching out on its own evolutionary adventure” (p. 210-211, italics in original).

Consistent with the contention that eugenic fertility is favoured under conditions of inter-group conflict, where group selection acts to promote cultures in which socially altruistic individuals are fairly prevalent, these collectivist eugenicists believed that it was necessary to increase the frequency of group selected altruistic phenotypes at the expense of individually selected ones. Even though the signatories of the Eugenicist’s Manifesto were universalists in that they clearly considered mankind to be their unit of collectivity, and were explicit in their desire to see conflict eliminated, the practice o...

Table of contents

• Cover
• Title
• Copyright
• Contents
• Summary
• 1. Introduction
• 2. Methods
• 3. Results
• 4. Discussion
• 5. Conclusions
• Appendix A
• Appendix B
• Glossary of new terms
• References