At Our Wits' End, page 5
20 Kirasic, K. (1989) Acquisition and utilization of spatial information by elderly adults: Implications for day to day situations, in Poon, L., Rubin, D. and Wilson, B. (eds.) Everyday Cognition in Adulthood and Later Life, Cambridge: Cambridge University Press.
21 Source: https://commons.wikimedia.org/wiki/File:IQ_curve.svg.
22 We are grateful to Satoshi Kanazawa for this metaphor, which he presented in Kanazawa, S. (2012) The Intelligence Paradox: Why the Intelligent Choice Isn’t Always the Smart One, Hoboken, NJ: John Wiley & Sons, p. 39.
23 See: Jensen, A.R. (2013) Rushton’s contributions to the study of mental ability, Personality & Individual Differences, 55, pp. 212–217.
24 See: Jensen, A.R. (1998) The g Factor: The Science of Mental Ability, Westport, CT: Praeger. For ‘reaction times’ and intelligence, see: Jensen, A.R. (2006) Clocking the Mind: Mental Chronometry and Individual Differences, New York: Elsevier.
25 Jensen, A.R. (2006) Clocking the Mind: Mental Chronometry and Individual Differences, New York: Elsevier.
26 Eysenck, H. (1998) Intelligence: A New Look, Piscataway, NJ: Transaction Publishers, Ch. 4.
27 Deary, I. (2000) Looking Down on Human Intelligence: From Psychometrics to the Brain, Oxford: Oxford University Press.
28 See: Ganley, C., Mingle, L.A., Ryan, A.M., Ryan, K., Vasilyeva, M. & Perry, M. (2013) An examination of stereotype threat effects on girls’ mathematics performance, Developmental Psychology, 49, pp. 1886–1889.
29 Jensen, A.R. (1981) Straight Talk About Mental Tests, New York: Free Press.
30 Herrnstein, R. & Murray, C. (1994) The Bell Curve: Intelligence and Class Structure in American Life, New York: Free Press.
31 Harmon, L.R. (1961) The high school background of science doctorates: A survey reveals the influence of class size, region of origin, as well as ability, in PhD production, Science, 133, pp. 679–688.
32 This latter point was made in: Vanhanen, T. (2009) The Limits of Democratization: Climate, Intelligence and Resource Distribution, Augusta, GA: Washington Summit Publishers.
33 Bouchard Jr., T.J. (2004) Genetic influence on human psychological traits, Current Directions in Psychological Science, 13, pp. 148–151.
34 Bouchard Jr., T.J. (1998) Genetic and environmental influences on adult intelligence and special mental abilities, Human Biology, 70, pp. 257–279.
35 Dahl, R. (1988) Matilda, London: Jonathan Cape.
36 Davies, G., Tenesa, A., Payton, A., Yang, J., Harris, S.E., Liewald, D. & Deary, I.J. (2011) Genome-wide association studies establish that human intelligence is highly heritable and polygenic, Molecular Psychiatry, 16, pp. 996–1005. For a book length discussion of the influence of parental intelligence on that of their children, see: Flynn, J.R. (2016) Does Your Family Make You Smarter? Cambridge: Cambridge University Press.
37 See: Rushton, J.P. (1989) Genetic similarity, human altruism, and group selection, Behavioral & Brain Sciences, 12, pp. 503–518.
38 Helgason, A., Palsson, S., Gudbjartsson, D., et al. (2008) An association between the kinship and fertility of human couples, Science, 319, pp. 813–816.
39 Vinkhuyzen, A.A.E., Sluis, S., van der Maes, H.H.M. & Posthuma, D. (2012) Reconsidering the heritability of intelligence in adulthood: Taking assortative mating and cultural transmission into account, Behavior Genetics, 42, pp. 187–198.
40 Jensen, A.R. (1997) The puzzle of nongenetic variance, in Sternberg, R.J. & Grigorenko, E.L. (eds.) Heredity, Intelligence, and Environment, Cambridge: Cambridge University Press, pp. 42–88.
41 Weiss, V. (1992) Major genes of general intelligence, Personality & Individual Differences, 13, pp. 1115–1134.
42 Buss, D.M. (2003) The Evolution of Desire: Strategies of Human Mating, New York: Basic Books.
43 See: Rushton, J.P. (1989) Genetic similarity, human altruism, and group selection, Behavioral & Brain Sciences, 12, pp. 503–518.
44 Okbay, A., Beauchamp, J.P., Fontana, M.A., Lee, J.J., Pers, T.H., Rietveld, C.A. & Benjamin, D.J. (2016) Genomewide association study identifies 74 loci associated with educational attainment, Nature, 533, pp. 539–542.
45 Gilbert, W.S. (1889) The Gondoliers.
46 See: Eliade, M. (2004) Shamanism: Archaic Technique of Ecstasy, Princeton, NJ: Princeton University Press.
Three
How and Why Has Intelligence Been Selected For?
Why are some animals more intelligent than others? Where does intelligence come from? In order to understand this we have to understand the general principles of Darwinian selection as set out by Charles Darwin.
There are two processes by which a population of animals are kept healthy, and adapted to their environment. Those that have genetic traits, which help them to survive in the face of particular environmental challenges, or are simply healthier, will live longer and have more children. This will happen every generation and it is known as natural selection. As part of this, those who have genetic disorders, or poor immunity, will be—along with their genes—constantly eliminated from the population. This is because they won’t survive childhood and, if they do, they won’t have many children or indeed any at all. Furthermore, there is a tendency for mothers to refuse to feed, and even to simply kill, obviously unhealthy offspring; the so-called runts of the litter. In this way, it is ensured that only the ‘fittest’—i.e. those with the greatest potential for reproduction—survive, because resources are not given to those with little chance of survival.
Fitness is reflected in the degree to which an organism is healthy and adapted to the environment. Genes are copied during the process of procreation, but these will sometimes be copied incorrectly and you end up with a mutant gene. If this mutant gene confers some benefit—such as greater strength (where this is needed) or a better immune system—it will spread throughout the population. But, in general, animals are relatively ‘fine-tuned’ with respect to the survival requirements imposed upon them by their environment, so a mutant gene will more often than not be bad. The organism will work less well. So, the healthy organism has a low percentage of mutant genes: a low ‘mutational load’.
Sexual Selection
There are a number of forms of selection. Darwin’s first book, On the Origin of Species, in 1858, popularised the idea of evolution and gave us the concept of ‘natural selection’. His second book, in 1871, was entitled, The Descent of Man and Selection in Relation to Sex. This gave us the equally important concept of ‘sexual selection’.
In most animal species, males will compete—fight—to mate with as many females as possible. In winning these fights, they establish who among them is strongest, healthiest, and who likely has very few mutant genes. Females will prefer the males who are successful in these fights because they will provide them with healthier offspring who are more likely to survive. The population will remain healthy and strong, because those who lack these qualities will be unsuccessful in their attempts to persuade females to mate with them. The females will actively fight off any attempt by an unhealthy male to breed with them. In much the same way, the human female will fight off attempts by unattractive (in whatever sense) males to breed with her. And, when they do so anyway, she has been raped—this being considered an appalling violation in most human societies.[1]
Darwin himself observed that, ‘It is certain that among all animals there is a struggle between the males for possession of the female.’[2] Throughout animal species, males compete for territory or, in the case of more social animals, the group competes for territory but each male competes for status within the male hierarchy of the group. Only those who are successful in gaining territory, where there is a limited amount of territory, or status within the hierarchy will be attractive to the females. In addition, the females will be specifically attracted to the qualities which lead to the males obtaining status. These will be markers of physical strength—in a society where status in obtained by fighting—and good genetic health. Males can showcase these qualities through fighting in front of the females but also by strutting; by advertising their genetic quality. This issue has long fascinated evolutionary psychologists (psychologists who attempt to explain the evolution of widespread, and thus likely evolved, psychological traits).[3]
A good example of males showcasing attractive physical qualities—examined by the American evolutionary psychologist Geoffrey Miller —is the peacock’s tail. This may have some use in terms of natural selection, in that the peacock can make himself look frightening to predators by displaying a particularly large tail with eye-shapes on it. However, it is also a ‘fitness indicator’. A peacock with poor genetic fitness—and thus a high number of mutant genes—would have to invest proportionately more of its resources into simply staying alive than a peacock with fewer mutant genes, because the body and mind of the mutant peacock would function less efficiently. As such, it would not be able to grow or maintain as impressive a tail. The tail of a less fit peacock would be smaller, less bright, less ornate, and less symmetrical. This is because we are evolved to be symmetrical; so symmetry is correlated with a lack of mutant genes (which interfere with the normal course of development) and it shows that the organism is fit enough to have acquired a healthy (symmetrical) phenotype in the face of disease or food shortage. With these considerations in mind, the tail would tell the peahen a great deal about the fitness of the peacock and we would expect the peahen to (1) select for peacocks that had such an ornament and (2) select for peacocks with the biggest and brightest tails.[4] A peacock’s tail is also a ‘costly signal’ of the peacock’s fitness. It is a way of saying, ‘My genes are of such good quality that I have resources left over to grow this fantastic tail and deal with the potential problems that it may cause, such as weighing me down while I am trying to escape from a predator!’
Social Selection
Another type of Darwinian selection that was clearly described (but not named) by Darwin in his 1871 book is social selection. This type of selection occurs when individuals enter into social alliances, compete for social resources, compete for status, and go to war.[5] It involves competing against other members of your own, or another, society. Most obviously, if people who are able to become richer than other people are, therefore, more likely to end up with more surviving children, then this is a matter of social selection.
The ways in which social selection can impact human populations are many—humans being an intensely social species. Traits like altruism and virtue were likely to have been very strongly shaped by social selection—the ways in which your fellow man acts on your behalf are going to have a big effect on your chances of leaving descendants, especially when such actions entail the sharing of scarce resources, protection from violence, or the formation of cooperative alliances.
It is important to keep in mind that natural, social, and sexual selection are not mutually exclusive to one another—in fact they are always related to one another via a sequalae—or causal chain. For example, let’s imagine that a population of social organisms is all of a sudden afflicted with a new disease. This source of natural selection will immediately kill all those who lack any kind of intrinsic resistance to it. However, because the population is highly social, individuals who are more altruistically inclined may aid those who are ill, putting themselves at risk in the process. The aid may increase the proportion of surviving organisms and hence social selection will work to increase the fitness of the recipients of the aid. The altruists are also producing costly social signals of their altruism (by allocating effort to the sick and putting themselves at risk in the process), which increases their odds of being sexually selected for on the basis that the altruistic traits are proxies for having good quality genes conferring a strong immune system. Therefore natural selection entails social selection, which in turn entails sexual selection. The disease weeds out those with weak immune systems, creating opportunities for the less vulnerable to benefit from the protective actions of the altruists, who in turn reap an extra fitness boost on the basis of having had the opportunity to display their fitness to prospective mates.
Group Selection
‘Group selection’ is an important manifestation of social selection. People who lay down their lives for their group are operating a ‘group selection’ strategy. By ‘group selection’ we mean selection for groups composed of individuals with certain traits. These are called ‘trait-groups’. There will be inter-group differences in the group averages of these traits, leading to some groups being more successful at passing on their genes than others. Unlike the classical group selection model, trait groups are comprised of variable numbers of individuals and their compositions can change over time. The fitness of the group can increase or decrease based on the change of its composition. This is because the composition of the group alters the relative strength of individual versus group selection, because an increase in individuals with certain traits may reduce or increase the group’s average level of, for example, altruism.
Broadly, this is part of multi-level selection. This refers to the way in which selection can occur at many levels such as the individual, the kinship group, the ethnic group, and the species.[6] They are making sure that their group survives and in doing so, as we will see later, they are indirectly passing on their genes. In much the same way, people who come up with a brilliant invention which allows their group to prosper and expand are following, whether consciously or not, a group selection strategy: they are aiding the survival of their group. Group selection happens when two groups come into conflict and must compete for scarce resources. Certain qualities, such as the desire to engage in self-sacrifice for the group, superior organisation, or abilities that lead to the production of better weapons, will allow one group to triumph over the other. There is evidence, as we will see later, that people differentially select in favour of their kin. Group selection extends this to the ethnic group, which is generally an extended kinship group.[7]
Selection for Intelligence in Animals
With these principles in mind, we can also understand how a certain optimum level of intelligence will be selected for among different species. There will be differences in general intelligence within the species and the less intelligent are likely to be weeded out in cases where there are clear benefits to being able to tackle and solve complex problems. This is not just speculation. We know there are individual differences in general intelligence within particular animal species and sub-species. This has been demonstrated in mice, racoons, pigeons, ravens, and chimpanzees and most recently it has been comprehensively demonstrated in the breed of dog known as border collies.[8]
British psychologist Rosalind Arden, of King’s College London’s Institute for Psychiatry, and her team procured 68 border collies in Wales aged between 1 and 12 years. This is a relatively large number for animal studies of this kind. Testing them in a purpose-built barn, each of the border collies was given a series of problems to solve, all of which were rewarded with a food treat. One test measured spatial intelligence (the dogs had to get a treat from behind a screen), a second measured behavioural inference (going to a beaker pointed to by a human), and the third measured quantity discrimination (how often the dog would go to the larger of two piles of food). Arden’s team found a clear g-factor among dogs. In general, those dogs which performed one of the tasks more quickly or accurately also did so in the other two tasks. This has clear implications for border collies because the more intelligent ones are kept as sheep dogs while the less intelligent ones end up being pets. But this clearly shows that there are real intelligence differences between individual animals of the same breed. This would have obvious effects in terms of survival in the wild because the more intelligent dogs would be more likely to survive and accrue territory. Related to this is research which has re-examined a study of general intelligence among 99 chimpanzees. The team found that the tasks administered to the chimpanzees which were the best measures of g among chimpanzees—that is, those which were more g-loaded—were also more heritable, based on estimates derived from the same chimpanzees.[9] So, there is not only variability in non-human general intelligence, but it is partly heritable, meaning it can be selected for.
Based on these studies, it is quite reasonable to argue that in every generation, the animals that are extremely impulsive or generally have very low intelligence are much more likely to take silly risks and get themselves killed, meaning that they don’t pass on their genes. Intelligence will also become important in terms of moving up the status hierarchy, although intelligence will be more important the more developed the animal is. In a troupe of chimpanzees, typically numbering 20 to 50, there will emerge a dominant male who will stay in place until he is successfully defeated by a middle ranking male. The successful ‘Young Turk’ must carefully judge when it is optimum to present his challenge to the alpha male. If he makes it when he is too young, or hasn’t developed enough support among subordinate males, then he may be killed or seriously injured in the resulting fight. If he leaves it too late, he may be too physically weak due to age and will also lose the fight. To strike at precisely the right time requires forethought, impulse control, and social skill—such that alliances with other chimps can be developed—and the careful calculation of possible consequences.[10] These are all signs of intelligence and so we would expect a certain level of average intelligence to be maintained among chimpanzees, with the less intelligent almost always failing to breed, or failing to breed to any significant extent. The alpha male will be the most attractive to females and will fight subordinate males who attempt to have sex with the females, though some will still manage to do so behind his back or may even be permitted to do so to maintain an alliance.
