Genetic similarity, human altruism, and group selection

Genetic similarity, human altruism, and group selection

J. Philippe Rushton (1989)

Abstract: A new theory of attraction and liking based on kin selection suggests that people detect genetic similarity in others in order to give preferential treatment to those who are most similar to themselves. There are many sources of empirical and theoretical support for this view, including (1) the inclusive fitness theory of altruism, (2) kin recognition studies of animals raised apart, (3) assortative mating studies, (4) favoritism in families, (5) selective similarity among friends, and (6) ethnocentrism. Specific tests of the theory show that (1) sexually interacting couples who produce a child are genetically more similar to each other in blood antigens than they are either to sexually interacting couples who fail to produce a child or to randomly paired couples from the same sample; (2) similarity between marriage partners is most marked in the more genetically influenced of sets of anthropometric, cognitive, and personality characteristics; (3) after the death of a child, parental grief intensity is correlated with the child’s similarity to the parent; (4) long-term male friendship pairs are more similar to each other in blood antigens than they are to random dyads from the same sample; and (5) similarity among best friends is most marked in the more genetically influenced of sets of attitudinal, personality, and anthropometric characteristics. The mechanisms underlying these findings may constitute a biological substrate of ethnocentrism, enabling group selection to occur.

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Genetic Influence on Risk of Divorce

Genetic Influence on Risk of Divorce

Matt McGue and David T. Lykken (1992)

Department of Psychology, University of Minnesota

Abstract – Although it has long been recognized that there is increased risk of divorce among the children of divorced parents, the extent to which genetic and environmental factors contribute to this familial resemblance has been a matter of speculation only. In order to resolve the separate influence of genetic and environmental factors on risk of divorce, divorce status of 1,516 same-sex twin pairs (722 monozygotic. MZ, and 794 dizygotic, DZ), their parents, and their spouses’ parents was determined. Concordance for divorce was significantly higher in MZ than DZ twins; this was true overall, in both the male and female samples, for both younger and older twin pairs, and both when the twins’ parents had been divorced and when they had not been divorced. The robustness and magnitude of the MZ-DZ difference in divorce concordance indicates a strong influence of genetic factors in the etiology of divorce. Moreover, family background of both spouses contributed independently to couples’ divorce risk, suggesting that, in many cases, divorce may be largely the result of characteristics the two spouses bring to the union rather than to interaction effects. These results also suggest that the adjustment difficulties seen with some children of divorced parents may be dice to an interaction between genetic and environmental factors rather than environmental influences alone, as is assumed in many theories of divorce’s effects.

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Do People Make Environments or Do Environments Make People?

Do People Make Environments or Do Environments Make People?


ABSTRACT: This article discusses the influence of people’s genetic make-up on their mental states of happiness and depression. Contrary to the conventional wisdom, great fortune does not guarantee happiness; neither does great misfortune assure depression. Emotional states are surprisingly immune to “objective” social circumstances. A biological basis for this relative immunity is that people possess biological set points for these emotional states, rendering the effects of most life events transitory. Genotypes also have indirect effects. People react differently to psychological stressors depending on their genotypes. A susceptible person may succumb to depression, whereas a resilient person may remain unaffected. People also expose themselves to different social environments. Exposure to controllable life events is partly a result of genetic predispositions. Consilience requires that this biological individuality be considered in any understanding of human behavior, including the pursuit of happiness.

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Genetic influences on ‘environmental’ factors

Genetic influences on ‘environmental’ factors

A. A. E. Vinkhuyzen, S. van der Sluis, E. J. C. de Geus, D. I. Boomsma and D. Posthuma (2009)

Childhood environment, social environment and behavior, leisure time activities and life events have been hypothesized to contribute to individual differences in cognitive abilities and physical and emotional well-being. These factors are often labeled ‘environmental’, suggesting they shape but not reflect individual differences in behavior. The aim of this study is to test the hypothesis that these factors are not randomly distributed across the population but reflect heritable individual differences. Self-report data on Childhood Environment, Social Environment and Behavior, Leisure Time Activities and Life Events were obtained from 560 adult twins and siblings (mean age 47.11 years). Results clearly show considerable genetic influences on these factors with mean broad heritability of 0.49 (0.00–0.87). This suggests that what we think of as measures of ‘environment’ are better described as external factors that might be partly under genetic control. Understanding causes of individual differences in external factors may aid in clarifying the intricate nature between genetic and environmental influences on complex traits.

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The Savanna Principle

The Savanna Principle

Satoshi Kanazawa
Manage. Decis. Econ. 25: 41–54 (2004)


For instance, one of the entities that we know for sure did not exist in the EEA is television. The fundamental principles of EP would therefore imply that humans have difficulty recognizing and dealing with TV. This indeed appears to be the case. People who watch certain types of TV shows are more satisfied with their friendships, just like they are if they have more friends or spend more time socializing with them in real life. It appears that the human brain has difficulty distinguishing between real friends and imaginary ones they see on TV, because it did not exist in the EEA (Kanazawa, 2002). It is this fundamental observation, that our brain and its psychological mechanisms are strongly biased to view and respond to the environment as if it were still the EEA, which leads to the Savanna Principle.

It is true, as critics of EP often point out, that the EEA, tens of thousands of years past, is not directly observable. We can make inferences about it, based both on archeological records and ethnography of contemporary hunter-gatherer societies, but it is unlikely that we will ever know all the details of the EEA. It is therefore impossible for us to draw all the implications of the above observation for our current social behavior. However, there are certain things about our ancestral life in the EEA that we know reasonably well. We know that our ancestors lived in small bands not exceeding 200 individuals; they did not live in a metropolis where everybody can be anonymous. We know that all communications between people in the EEA were direct and face-to-face; they did not have telephones, computers or even writing that allowed them to communicate without facing each other. It is my suggestion in this paper that these few facts that we know about the EEA are sufficient to use the Savanna Principle to figure out which hypotheses about human behavior are likely to fail and why.

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De Gustibus Est Disputandum

De Gustibus Est Disputandum

SATOSHI KANAZAWA, Indiana University of Pennsylvania, 2001.

Principles of Evolutionary Psychology

Our preference for sweets and fats is an example of an evolved psychological mechanism (Barash 1982:144-47). Throughout most of human evolutionary history, procurement of sufficient calories to sustain our bodies physically was a particularly severe problem of adaptation (survival); malnutrition was a common problem. In this environment, those who had a “taste” for sweets and fats (which have higher calories) were better off physically than those who did not have the same taste. Those who had this taste therefore lived longer, led healthier lives and produced higher-quality offspring than those who didn’t. They in turn passed on their taste to their offspring, over many thousands of generations, until most of us living today have a strong preference for sweets and fats. (See Buss 1995:5-9 for other examples of evolved psychological mechanisms.)

Note that we do not consciously choose or decide to like sweets and fats. We just like them but otherwise don’t know why; sweet and fatty foods just taste good to us. […]

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Social sciences are branches of biology

Social sciences are branches of biology

Satoshi Kanazawa, 2004.

3. Puzzles: wage penalty for motherhood, wage reward for fatherhood (and bigger reward from boys than girls)

In a recent study, Budig and England (2001) find that mothers earn less than non-mothers with similar characteristics. The negative effect of motherhood on wage is greater for married mothers than for unmarried mothers. Their finding is in stark contrast to Lundberg and Rose’s (2000) discovery that fathers earn more than non-fathers with similar characteristics. In other words, there appears to be a wage penalty for motherhood and a wage reward for fatherhood.

Both Budig and England (2001) and Lundberg and Rose (2000) use a statistical technique called the fixed-effect model. By using two data points for each individual, before and after parenthood, the fixed-effect model controls for all unobserved heterogeneity, and allows these authors to rule out the possibility of selection bias. In other words, Budig and England (2001) demonstrate that it is not because women with lower earning capacities are more likely to become mothers that mothers earn less than non-mothers, and Lundberg and Rose (2000) demonstrate that it is not because men with higher earning capacities are more likely to become fathers that fathers earn more than non-fathers. It is motherhood itself that reduces wages, and it is fatherhood itself that increases them.

Further, Lundberg and Rose (2002) find, once again using the fixed-effect model, that such ‘wage reward’ for fatherhood is greater if the men have boys than if they have girls. Men earn more, and work longer hours, in response to the birth of sons than to that of daughters. What accounts for these peculiar patterns? What explains the puzzling fact that motherhood carries a wage penalty but fatherhood carries a wage reward, and that such wage reward for fatherhood is greater if the men have sons than if they have daughters?

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Precautionary principle : An Evolutionary Perspective

In his 2010 paper, “Why Liberals and Atheists Are More Intelligent”, Kanazawa stated :

When our ancestors faced some ambiguous situation, such as rustling noises nearby at night or a large fruit falling from a tree branch and hitting them on the head, they could attribute it either to impersonal, inanimate, unintentional forces (wind blowing gently to make the rustling noises among the bushes and leaves, a mature fruit falling by its own weight from the branch by the force of gravity and hitting them on the head purely by accident) or to personal, animate, intentional forces (a predator sneaking up on them to attack, an enemy hiding in the tree branches and throwing fruits at their head).

Given that the situation is inherently ambiguous, our ancestors could have made one of two errors of inference. They could have attributed the events to intentional forces when they are in fact caused by unintentional forces (false-positive or Type I error) or they could have attributed them to unintentional forces when they were in fact caused by intentional forces (false-negative or Type II error). The consequences of Type I errors were that our ancestors became unnecessarily paranoid and looked for predators and enemies where there were none. The consequences of Type II errors were that our ancestors were attacked and killed by predators or enemies when they least suspected an attack. The consequences of committing Type II errors are far more detrimental to survival and reproduction than the consequences of committing Type I errors. Evolution should therefore favor psychological mechanisms which predispose their carriers to commit Type I errors but avoid Type II errors, and thus overinfer (rather than underinfer) intentions and agency behind potentially harmless phenomena caused by inanimate objects. Evolutionarily speaking, it is good to be paranoid, because it might save your life (Haselton and Nettle 2006).

Recent evolutionary psychological theories therefore suggest that evolutionary origin of religious beliefs in supernatural forces may stem from such an innate bias to commit Type I errors rather than Type II errors. The human brain may be biased to perceive intentional forces (the hands of God at work) behind a wide range of natural physical phenomena whose exact causes are unknown. If these theories are correct, then it means that religion and religiosity have an evolutionary origin. It is evolutionarily familiar and natural to believe in God, and evolutionarily novel not to be religious.

Then, if the precautionary principle, so often despised by economists, is evolutionarily familiar, it appears that this attitude is highly beneficial because this will improve our reproductive success. As such, ideology like liberalism is maladaptative; by promoting unnatural attitude, it tends to decrease our reproductive success, unless the relation has been distorted by government’s laws (an example of this is provided by Kanazawa & Savage, 2009, p. 122). This is why liberalism correlates with higher IQ, and this is why high IQ is detrimental. Not surprising if the so-called “racism” correlates with low IQ. Given the precautionary principle, it is natural to distrust strangers. Again, this is because the consequence of Type II errors (thinking that the danger is not there when it is) does not worth the risk.